Which of the Following Allows a Pregnant Mother to Provide Oxygen to Her Developing Baby?

Cochrane Database Syst Rev. 2012 Dec; 2012(12): CD000136.

Maternal oxygen assistants for fetal distress

Monitoring Editor: Bukola Fawole, 1000 Justus Hofmeyr, and Cochrane Pregnancy and Childbirth Grouping

University of Ibadan, Department of Obstetrics and Gynaecology, College of Medicine, IbadanNigeria

University of the Witwatersrand, Academy of Fort Hare, Eastern Cape Department of Wellness, Section of Obstetrics and Gynaecology, Due east London Hospital Circuitous, Frere and Cecilia Makiwane Hospitals, Individual Bag X 9047, East LondonEastern CapeSouth Africa, 5200

Abstract

Background

Maternal oxygen administration has been used in an endeavor to lessen fetal distress past increasing the available oxygen from the mother. This has been used for suspected fetal distress during labour, and prophylactically during the second phase of labour on the supposition that the 2nd stage is a time of high risk for fetal distress.

Objectives

The objective of this review was to assess the furnishings of maternal oxygenation for fetal distress during labour and to appraise the furnishings of condom oxygen therapy during the second phase of labour on perinatal result.

Search methods

We searched the Cochrane Pregnancy and Childbirth Grouping'due south Trials Register (22 Oct 2012) and searched reference lists of retrieved studies.

Selection criteria

Randomized trials comparing maternal oxygen administration for fetal distress during labour and prophylactic oxygen administration during the 2nd stage of labour with a control grouping (dummy or no oxygen therapy).

Data collection and analysis

Both review authors assessed eligibility and trial quality. Data were extracted, checked and entered into Review Manager software. For dichotomous data, we calculated relative risks (RR) and 95% confidence intervals (CI). For continuous data, we calculated weighted mean differences and 95% CI.

Chief results

We located no trials addressing maternal oxygen therapy for fetal distress. We included two trials which addressed prophylactic oxygen assistants during labour. Abnormal string blood pH values (less than 7.2) were recorded significantly more than oft in the oxygenation group than the control group (RR 3.51, 95% CI i.34 to 9.19). In that location were no other statistically significant differences betwixt the groups. There were conflicting conclusions on the effect of the elapsing of oxygen administration on umbilical avenue pH values betwixt the two trials.

Authors' conclusions

Implications for practice
In that location is not enough evidence to support the employ of condom oxygen therapy for women in labour, nor to evaluate its effectiveness for fetal distress.

Implications for research
In view of the widespread use of oxygen administration during labour and the possibility that it may be ineffective or harmful, at that place is an urgent need for randomized trials to assess its effects.

Plain language summary

Maternal oxygen administration for fetal distress

Too fiddling evidence to show whether oxygen administration to the woman during labour is beneficial to the babe.

Some babies show signs of distress, such as unusual heart rates or the passing of a bowel motion (meconium) during their mother'due south labour. This may exist caused past a lack of oxygen passing from the woman to the baby through the placenta. Sometimes, women may be encouraged to exhale extra oxygen through a facemask (oxygen administration) to increase the oxygen bachelor to the unborn babe. A review of two trials found too piddling evidence to show whether oxygen administration to the adult female during the 2nd phase of labour is benign to the baby. No trials of oxygen assistants when the baby is showing signs of distress were constitute. Further inquiry is needed.

Background

The diagnosis of suspected fetal distress during labour, usually on the basis of fetal heart rate parameters or fetal scalp claret pH measurement, is always considered an emergency. The importance fastened to information technology derives from the perceived association of fetal hypoxia (low oxygen levels) with perinatal morbidity/mortality and long‐term disability (Marlow 1999).

Physiological studies support the notion of a human relationship between maternal oxygenation and fetal wellbeing. In a randomized cross‐over written report, fetal habituation to vibroacoustic stimulation was normal in 17 of 18 women with normal pregnancies at term, but in only two of the 18 when breathing a 12% oxygen in nitrogen mixture (Leader 1988). Thus, among other measures, maternal oxygen therapy is commonly employed, albeit empirically, in the clinical management of suspected fetal distress. So deeply entrenched is its utilize in clinical exercise that healthcare workers virtually intuitively administer oxygen at the first suspicion of fetal distress. Oxygen administration has also been used prophylactically in the second stage of labour on the assumption that this is a time of high risk for fetal distress.

Despite this widespread use, controversy persists concerning the benefits of administered maternal oxygen for the fetus. Some studies suggest a beneficial effect (Althabe 1967; Gare 1969; McNamara 1993; Willcourt 1983). Other authors report otherwise. Saling 1963 attributed the transient rise in partial pressure of oxygen (PO2) followed by a simultaneous drib in fetal pH and a rising in fractional pressure level of carbon dioxide (PCO2) afterwards maternal oxygen therapy to the effects of hypoxia‐induced vasoconstriction of placenta vessels. Perreault 1992 constitute no consequence on umbilical string blood gas values post-obit a brief period of maternal hyper‐oxygenation immediately before caesarean section. Estimation of these studies is difficult every bit they were conducted in diverse clinical settings, and applying differing methodologies and variable biochemical techniques for blood gas and fetal acid‐base of operations assessment. Extrapolating from creature studies, Lofaso 2007 cautions that the inhibitory effects of hyperoxia may compromise oxygenation afterward oxygen administration, particularly in preterm infants. However, Simpson 2005 demonstrated increased fetal oxygen saturation following maternal oxygen administration during the starting time phase of labour. The increment was more pronounced in fetuses with fetal oxygen saturation less than 40%, compared with those with college oxygen content. This effect was reported to persist for more than half an hour after the oxygen was discontinued.

In support of the argument that maternal oxygen therapy has an observable effect on fetal oxygenation, Meschia 1999 contends that when the oxygen content is considered rather than focusing on fetal PO2 changes lone, oxygen therapy tin can cause similar increments in maternal and fetal blood. Glazier 1999 describes the oxygen content of the blood perfusing the placenta from the umbilical arteries as the single most of import determinant of oxygen transfer from maternal to fetal blood.

Given the electric current level of uncertainty about the use of oxygen during labour, it is not strange that the indications, duration, mode of administration and the optimal concentration remain contentious. Surprisingly, no randomized clinical trials accept to our knowledge assessed the effectiveness of maternal oxygen therapy for fetal distress.

This review evaluated the effects of maternal oxygen therapy during labour in women with or without suspected fetal distress.

Objectives

To appraise, from the all-time available evidence, the effects of maternal oxygen therapy for fetal distress (part 1), and prophylactic maternal oxygen therapy (part 2), on intervention rates and neonatal outcome.

Methods

Criteria for considering studies for this review

Types of studies

All published, unpublished and ongoing randomized controlled trials comparison the outcome of maternal oxygen administration for fetal distress during labour (part 1) and rubber oxygen administration during the second stage of labour (office 2) on clinically meaningful outcomes, with a control group (dummy or no oxygen therapy); with adequate allocation concealment; violations of allocated management and exclusions after allocation not sufficient to materially bear on outcomes. We excluded quasi‐randomized trials (due east.1000. those randomized by engagement of birth or hospital number) from the assay.

Types of participants

Office 1: women with suspected fetal distress during or prior to labour.
Part 2: women without suspected fetal distress during the second stage of labour.

Types of interventions

Maternal oxygen administration versus dummy or no oxygen administration.

Types of outcome measures

The following measures of intervention and neonatal well‐existence were prespecified:

1. assisted vaginal delivery;

2. caesarean section;

3. maternal dissatisfaction;

4. abnormal fetal heart charge per unit tracing;

5. cord arterial pH less than seven.2;

6. Apgar score less than seven at one minute;

7. Apgar score less than seven at 5 minutes;

8. neonatal resuscitation;

9. neonatal encephalopathy;

10. serious neonatal morbidity or expiry;

11. babyhood disability.

Nosotros included the outcomes if clinically meaningful; reasonable measures were taken to minimise observer bias; missing data were insufficient to materially influence conclusions; data were available for analysis co-ordinate to original allocation, irrespective of protocol violations; data were available in a format suitable for analysis.

Search methods for identification of studies

Electronic searches

We searched the Cochrane Pregnancy and Childbirth Group's Trials Annals past contacting the Trials Search Co‐ordinator (22 October 2012).

The Cochrane Pregnancy and Childbirth Grouping'due south Trials Register is maintained by the Trials Search Co‐ordinator and contains trials identified from:

1. monthly searches of the Cochrane Key Register of Controlled Trials (CENTRAL);

2. weekly searches of MEDLINE;

3. weekly searches of EMBASE;

4. handsearches of 30 journals and the proceedings of major conferences;

5. weekly current awareness alerts for a further 44 journals plus monthly BioMed Central email alerts.

Details of the search strategies for Cardinal, MEDLINE and EMBASE, the listing of handsearched journals and conference proceedings, and the list of journals reviewed via the current sensation service can be found in the 'Specialized Register' section within the editorial information about the Cochrane Pregnancy and Childbirth Group.

Trials identified through the searching activities described higher up are each assigned to a review topic (or topics). The Trials Search Co‐ordinator searches the register for each review using the topic listing rather than keywords.

In the previous version of the review, nosotros too carried out an additional search of CENTRAL (The Cochrane Library 2007, Event 3). Please see Appendix i for search terms used.

Searching other resources

We conducted a transmission search of the reference lists of all identified papers.

We did non use whatever language restrictions.

Data collection and analysis

For the methods used in previous updates, please seeAppendix 2.

For the methods to exist used in future updates, please meetAppendix iii.

Selection of studies

Two review authors independently assessed for inclusion all the potential studies we identified as a result of the updated search. We resolved any disagreement through discussion.

No new studies were included equally part of this update.

Results

Clarification of studies

The search strategy identified half dozen reports of studies for potential inclusion. Sirimai 1997 prospectively randomized 160 women with normal labour to receive either oxygen throughout the 2d stage of labour or no oxygen. Thorp 1995 also randomized 86 women at the onset of the 2d phase of labour to receive oxygen administration past face mask or no oxygen. These two studies met the inclusion criteria for this review (see tabular array of 'Characteristics of included studies').

Iv studies (Jozwik 2000; Lawes 1988; Simpson 2005; Nesterenko 2012) were excluded from the review (see table of 'Characteristics of excluded studies'). Lawes 1988 investigated the effect of maternal oxygen concentration (50% versus 33%) on neonatal status in women who had caesarean department under general anaesthesia. This study was excluded because the study design was not randomized and thus did not come across the inclusion criteria for this review. Jozwik 2000 compared 17 women in the second stage of labour who were given oxygen past confront mask with 343 controls and 24 women scheduled for constituent caesarean section who had sixty% oxygen at 15 litres/minute for xv minutes compared with 116 controls. Nosotros excluded the study because information technology was non a randomized controlled trial. Simpson 2005 prospectively evaluated three intrauterine resuscitation techniques, namely administration of intravenous fluid, maternal position and oxygen administration. Maternal fluid administration and position were evaluated using randomized design, simply investigation of the furnishings of oxygen assistants was not past a randomized design. We too excluded this trial. In that location were ii study reports for the Nesterenko 2012 trial. This was a randomized, double‐blind, controlled study. Nesterenko 2012 investigated the effects of maternal oxygen administration (2L/min) for at least thirty minutes before commitment on maternal and umbilical cord claret concentrations of SOD and glutathione (GSSG); 30 women were randomized to Oxygen group and 26 women into the Room Air group. This trial was excluded because maternal oxygen administration was not for fetal distress and participants were not specifically stated to be in the second stage of labour.

Risk of bias in included studies

In the study of Thorp 1995, randomization was by sealed envelopes, but no further details were given. One woman randomized to the oxygenation group was excluded because of caesarean department for cord prolapse before total cervical dilation. An imbalance in the analgesia received by the oxygenation grouping compared with the command group is not accounted for (narcotic merely: 12% versus 41% in the control group, P < 0.05; epidural: 71% versus xviii%, respectively). No masking by ways of dummy oxygen therapy was used. Compliance with oxygen therapy was reasonable.

The method of randomization in the study of Sirimai 1997 was non stated. The written report was available in abstract grade only and contained minimal data for analysis. It was, however, included because there were not plenty good quality trials addressing the question. Interpretation of the findings from the trial consequently needs to exist done with circumspection.

Effects of interventions

We found no trials that assessed the effects of maternal oxygen therapy in fetal distress. 2 randomized trials (Sirimai 1997; Thorp 1995) assessed the use of safe maternal oxygen therapy during the second stage of uncomplicated labour. Randomization was not employed in a Polish trial (Jozwik 2000) that also assessed prophylactic maternal oxygen therapy during labour. We excluded this trial.

Nosotros sought all the prespecified outcomes listed under 'Types of consequence measures'. We included two additional outcomes (string arterial blood oxygen content (mg/dl) and cord arterial blood oxygen saturation (%)) after give-and-take betwixt the review authors.

Abnormal string claret pH values (< 7.two) were significantly more than frequent in the oxygenation group than the controls (relative risk 3.51, 95% conviction interval (CI) 1.34 to ix.19). There was a tendency towards reduced cord arterial blood oxygen content and oxygen saturation in mothers treated with oxygen compared with controls: weighted mean difference (WMD) ‐0.80, 95% CI ‐2.29 to 0.69 and WMD ‐4.40, 95% CI ‐11.22 to 2.42 respectively. Other blood gas parameters also tended to favour the control grouping. These differences betwixt the groups were not statistically significant.

Data on the issue of duration of oxygen administration were not presented in a compatible format suitable for combination. In the Thorp 1995 trial, those receiving oxygenation for less than 10 minutes had college umbilical artery pH values than those receiving oxygenation for longer than 10 minutes and the umbilical artery pH was as well significantly higher in infants receiving oxygenation for less than 10 minutes than controls. The duration of maternal oxygen administration had no effect on cord arterial blood pH in the Sirimai 1997 trial.

Discussion

There were conflicting observations about the furnishings of the duration of maternal oxygenation on cord arterial blood pH in the 2 trials. Whereas Thorp 1995 suggested that curt‐term oxygenation may be beneficial and long‐term oxygenation harmful, Sirimai 1997 reported that prolonged use of oxygen did non touch on fetal acid‐base of operations status. However, neither trial addressed the question of the duration of oxygen therapy in a randomized format. Thus the conclusions should exist regarded equally speculative.

It is difficult to depict firm conclusions from some of the measures of outcome in this review as they suffered from small-scale numbers or wide confidence intervals, or both. These included Apgar scores less than seven at 1 and five minutes, assisted vaginal commitment, caesarean section, and the string arterial blood oxygen saturation.

Maternal oxygen assistants did not significantly affect the cord claret arterial blood oxygen content and the need for neonatal resuscitation. Withal, at that place were significantly more infants whose mothers received oxygen with cord arterial pH less than 7.2 compared with the infants of controls.

Remarkably, no trials on maternal oxygen administration for fetal distress were identified.

Authors' conclusions

Implications for practice

The evidence available for this review does not support the use of prophylactic maternal oxygen therapy during labour. We are not aware of randomized clinical trials to guide practice concerning the therapeutic use of maternal oxygen therapy for fetal distress.

Implications for enquiry

In view of the widespread use of maternal oxygen therapy for fetal distress and the lack of consensus concerning its usefulness or possible harmfulness, it is virtually important that advisable randomized trials be carried out in this field. Trials should specify whether the supine position, which may impair fetal oxygenation, was systematically avoided.

In that location are apparent gaps between basic medical science information and clinical practise. The post-obit areas need elucidation upon which subsequent clinical research could be based.

1. The response of umbilical cord vessels to hyper‐oxygenation.

2. The effect of the duration of hyper‐oxygenation on umbilical cord vessels.

3. The effect of hyper‐oxygenation on umbilical cord blood gas and fetal acid‐base of operations status.

4. The assessment of the most reliable indicator(south) of materno‐fetal exchange and fetal well‐being.

Doppler studies may be a useful way to appraise the fetal response to maternal oxygen therapy.

What'south new

Date	Event	Description
12 November 2012	New citation required just conclusions have not changed	Ane new trial identified and excluded.
22 October 2012	New search has been performed	Search updated.

History

Protocol beginning published: Upshot 2, 1996
Review first published: Issue ii, 1996

Date	Issue	Description
11 February 2008	Amended	Converted to new review format.
30 June 2007	New search has been performed	We identified one new trial when nosotros reran the search in June 2007. The trial (Simpson 2005) was excluded in this update.
25 June 2003	New citation required and conclusions have changed	Noun amendment
23 June 2003	New search has been performed	We identified 2 new trials when we reran the search in March 2003. 1 has been included (Sirimai 1997) and one excluded (Jozwik 2000) in this update.

Appendices

Appendix 1. Primal search terms

Authors searched CENTRAL (The Cochrane Library 2007, Result 3) using the terms 'oxygen*' and 'maternal*' and 'fetal or foetal' and 'distress' .

Appendix 2. Methods of data collection and analysis used in previous versions

Data collection and analysis

Choice of studies

We independently assessed for inclusion all potential trials we identified equally a upshot of the search strategy, without consideration of the results. Nosotros resolved any disagreement through word.

Information extraction and management

We designed a form to extract data. Both authors independently extracted data using the agreed course. We resolved discrepancies through word. We used the Review Managing director software (RevMan 2003) to double enter all the data. When information regarding any of the above was unclear, we contacted the authors of the original reports to provide further details.

Assessment of gamble of bias in included studies

We assessed the validity of each report using the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2005). Methods used for the generation of the randomization sequence was described for each trial.

(1) Option bias (randomization and allocation concealment)

We assigned a quality score for each trial, using the following criteria:
(A) adequate concealment of allocation: such as telephone randomization, consecutively‐numbered sealed opaque envelopes;
(B) unclear whether acceptable concealment of resource allotment: such as list or table used, sealed envelopes, or study does not study any concealment approach;
(C) inadequate concealment of resource allotment: such every bit open listing of random‐number tables, use of instance record numbers, dates of nascency or days of the week.

(2) Attrition bias (loss of participant e.m. withdrawals, dropouts, protocol deviations)

Nosotros assessed completeness to follow up using the following criteria:
(A) less than 5% of loss of participants;
(B) v% to 9.9% of loss to follow upwards;
(C) ten% to nineteen.ix% loss of participants;
(D) more than twenty% loss of participants.

(3) Operation bias (blinding of participants, researchers and event cess)

Nosotros assessed blinding using the following criteria:
(ane) blinding of participants (yes/no/unclear);
(2) blinding of caregiver (yes/no/unclear);
(3) blinding of consequence assessment (yes/no/unclear).

Measures of handling effect

We carried out statistical analysis using the Review Director software (RevMan 2003). We used fixed‐effect meta‐assay for combining data in the absenteeism of pregnant heterogeneity if trials were sufficiently like. If nosotros found heterogeneity, we explored this past sensitivity assay followed by random‐furnishings if required.

Dichotomous data

For dichotomous information, nosotros presented results equally summary relative adventure with 95% conviction intervals (CI).

Continuous information

For continuous data, nosotros used the weighted hateful departure (WMD) when outcomes were measured in the same mode between trials. Nosotros intended to utilize standardized mean divergence to combine trials that measured the aforementioned outcome, but used different methods.

Dealing with missing information

We analyzed data on all participants with available information in the grouping to which they were allocated, regardless of whether or not they received the allocated intervention. If in the original reports participants were non analyzed in the group to which they were randomized, and there was sufficient data in the trial study, we restored them to the right group.

Assessment of heterogeneity

Nosotros applied test of heterogeneity betwixt trials using the I² statistic. Nosotros considered Iⁱⁱ values greater than 50% every bit indicating substantial heterogeneity (Higgins 2005).

Appendix three. Methods of data collection and analysis to be used in future updates of this review

Data collection and analysis

Selection of studies

2 review authors will independently appraise for inclusion all the potential studies nosotros identify as a result of the search strategy. Nosotros will resolve any disagreement through discussion or, if required, we will consult a third review author.

Data extraction and management

We volition pattern a form to excerpt data. For eligible studies, two review authors will excerpt the data using the agreed course. We will resolve discrepancies through discussion or, if required, we will consult the third review writer. Nosotros will enter information into Review Manager software (RevMan 2011) and cheque for accuracy.

When information regarding whatsoever of the in a higher place is unclear, nosotros will attempt to contact authors of the original reports to provide farther details.

Assessment of hazard of bias in included studies

Ii review authors volition independently assess risk of bias for each study using the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). We will resolve whatever disagreement past discussion or by involving a third assessor.

(1) Random sequence generation (checking for possible selection bias)

We will draw for each included study the method used to generate the allocation sequence in sufficient item to allow an cess of whether it should produce comparable groups.

We volition assess the method as:

• low chance of bias (any truly random procedure, e.g. random number table; computer random number generator);

• high risk of bias (any non‐random procedure, eastward.g. odd or fifty-fifty date of nascence; hospital or clinic tape number); or

• unclear risk of bias.

 (two) Allotment concealment (checking for possible selection bias)

We will depict for each included written report the method used to conceal allocation to interventions prior to assignment and volition assess whether intervention allotment could have been foreseen in accelerate of, or during recruitment, or changed later assignment.

We will assess the methods every bit:

• low risk of bias (e.k. telephone or central randomisation; consecutively numbered sealed opaque envelopes);

• high take a chance of bias (open random allocation; unsealed or non‐opaque envelopes, alternation; date of birth);

• unclear risk of bias.

(3.i) Blinding of participants and personnel (checking for possible operation bias)

We volition describe for each included study the methods used, if whatsoever, to blind study participants and personnel from noesis of which intervention a participant received. We volition consider that studies are at low adventure of bias if they were blinded, or if we judge that the lack of blinding would be unlikely to affect results. We volition appraise blinding separately for different outcomes or classes of outcomes.

We volition assess the methods as:

• low, high or unclear adventure of bias for participants;

• low, loftier or unclear risk of bias for personnel.

(three.2) Blinding of upshot cess (checking for possible detection bias)

We will describe for each included study the methods used, if whatsoever, to blind consequence assessors from knowledge of which intervention a participant received.  We volition assess blinding separately for different outcomes or classes of outcomes.

We will assess methods used to blind outcome assessment as:

• low, high or unclear risk of bias.

(iv) Incomplete consequence data (checking for possible attrition bias due to the amount, nature and handling of incomplete event data)

We will draw for each included study, and for each outcome or class of outcomes, the abyss of data including attrition and exclusions from the analysis. We will land whether attrition and exclusions were reported and the numbers included in the analysis at each stage (compared with the total randomised participants), reasons for attrition or exclusion where reported, and whether missing data were balanced across groups or were related to outcomes.  Where sufficient information is reported, or tin be supplied by the trial authors, we will re‐include missing data in the analyses which we undertake.

We will assess methods as:

• low risk of bias (e.g. no missing outcome data; missing outcome information counterbalanced beyond groups);

• high risk of bias (e.m. numbers or reasons for missing data imbalanced beyond groups; 'every bit treated' analysis done with substantial departure of intervention received from that assigned at randomisation);

• unclear risk of bias.

(five) Selective reporting (checking for reporting bias)

Nosotros will draw for each included study how we investigated the possibility of selective effect reporting bias and what nosotros found.

We volition appraise the methods as:

• depression risk of bias (where it is clear that all of the study's pre‐specified outcomes and all expected outcomes of involvement to the review take been reported);

• high adventure of bias (where not all the report's pre‐specified outcomes have been reported; one or more reported primary outcomes were not pre‐specified; outcomes of interest are reported incompletely and so cannot be used; report fails to include results of a key outcome that would take been expected to have been reported);

• unclear hazard of bias.

(6) Other bias (checking for bias due to problems not covered by (ane) to (5) higher up)

We will describe for each included study any of import concerns we have nearly other possible sources of bias.

We will appraise whether each study was free of other issues that could put it at take chances of bias:

• low risk of other bias;

• high risk of other bias;

• unclear whether there is risk of other bias.

(7) Overall take chances of bias

We will make explicit judgements virtually whether studies are at loftier chance of bias, according to the criteria given in the Handbook (Higgins 2011). With reference to (one) to (half-dozen) in a higher place, we will assess the likely magnitude and direction of the bias and whether we consider it is likely to impact on the findings.  We volition explore the impact of the level of bias through undertaking sensitivity analyses ‐ see Sensitivity analysis.

Measures of handling effect

Dichotomous data

For dichotomous data, we will present results as summary risk ratio with 95% confidence intervals.

Continuous data

For continuous data, we volition use the hateful divergence if outcomes are measured in the aforementioned way betwixt trials. We will use the standardised mean departure to combine trials that measure out the same consequence, merely employ different methods.

Dealing with missing data

For included studies, we will note levels of compunction. We volition explore the touch of including studies with high levels of missing information in the overall cess of treatment effect past using sensitivity analysis.

For all outcomes, we will bear out analyses, as far as possible, on an intention‐to‐treat footing, i.e. we will try to include all participants randomised to each group in the analyses, and all participants will be analysed in the grouping to which they were allocated, regardless of whether or not they received the allocated intervention. The denominator for each outcome in each trial will exist the number randomised minus any participants whose outcomes are known to exist missing.

Assessment of heterogeneity

Nosotros will assess statistical heterogeneity in each meta‐analysis using the T², I² and Chi² statistics. We will regard heterogeneity every bit substantial if I² is greater than 30% and either T² is greater than zero, or there is a low P value (less than 0.x) in the Chi² test for heterogeneity.

Assessment of reporting biases

If in that location are 10 or more than studies in the meta‐analysis we will investigate reporting biases (such as publication bias) using funnel plots. Nosotros volition appraise funnel plot asymmetry visually, and employ formal tests for funnel plot asymmetry. For continuous outcomes we will use the test proposed by Egger 1997, and for dichotomous outcomes we volition use the exam proposed by Harbord 2006. If disproportion is detected in any of these tests or is suggested by a visual assessment, we will perform exploratory analyses to investigate it.

Information synthesis

We will comport out statistical assay using the Review Manager software (RevMan 2011). We will use fixed‐effect meta‐assay for combining data where it is reasonable to presume that studies are estimating the same underlying treatment effect: i.e. where trials are examining the same intervention, and the trials' populations and methods are judged sufficiently similar. If there is clinical heterogeneity sufficient to expect that the underlying treatment effects differ between trials, or if substantial statistical heterogeneity is detected, nosotros will utilize random‐effects meta‐assay to produce an overall summary if an boilerplate treatment effect beyond trials is considered clinically meaningful. The random‐furnishings summary will be treated every bit the boilerplate range of possible handling furnishings and we volition discuss the clinical implications of treatment effects differing between trials. If the average treatment effect is non clinically meaningful nosotros will not combine trials.

If we use random‐effects analyses, the results volition be presented as the average handling effect with 95% confidence intervals, and the estimates of  T² and I².

Subgroup analysis and investigation of heterogeneity

If nosotros place substantial heterogeneity, we will investigate it using subgroup analyses and sensitivity analyses. We will consider whether an overall summary is meaningful, and if it is, utilise random‐effects assay to produce it.

Sensitivity analysis

We volition bear out sensitivity assay to explore the furnishings of trial quality assessed by allocation concealment and other risk of bias components, by omitting studies rated equally inadequate for these components. We will restrict this to the primary outcomes.

Notes

New search for studies and content updated (no alter to conclusions)

Data and analyses

Comparison 1

Maternal oxygen for fetal distress

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Assisted vaginal delivery	0	0	Run a risk Ratio (M‐H, Stock-still, 95% CI)	0.0 [0.0, 0.0]
2 Caesarean section	0	0	Risk Ratio (M‐H, Stock-still, 95% CI)	0.0 [0.0, 0.0]
iii Maternal dissatisfaction	0	0	Take chances Ratio (One thousand‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
iv Abnormal fetal centre rate tracing	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
5 Cord arterial pH < seven.2	0	0	Chance Ratio (Thou‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
6 Apgar score < 7 at 1 infinitesimal	0	0	Risk Ratio (Yard‐H, Stock-still, 95% CI)	0.0 [0.0, 0.0]
7 Apgar score < seven at 5 minutes	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
viii Neonatal resuscitation	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
ix Neonatal encephalopathy	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
10 Serious neonatal morbidity or death	0	0	Risk Ratio (Chiliad‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
xi Childhood inability	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]

Comparison 2

Safe maternal oxygen

Upshot or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Assisted vaginal delivery	i	85	Risk Ratio (G‐H, Stock-still, 95% CI)	1.07 [0.07, xvi.60]
2 Caesarean section	1	85	Take chances Ratio (M‐H, Fixed, 95% CI)	0.54 [0.05, 5.70]
three Maternal dissatisfaction	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
4 Aberrant fetal heart rate tracing	1	85	Risk Ratio (One thousand‐H, Stock-still, 95% CI)	1.25 [0.46, three.42]
5 Cord arterial pH < 7.2	two	245	Take a chance Ratio (Thousand‐H, Fixed, 95% CI)	3.51 [i.34, nine.19]
6 Apgar score < seven at 1 minute	i	85	Take a chance Ratio (M‐H, Fixed, 95% CI)	0.15 [0.01, 2.88]
7 Apgar score < 7 at five minutes	1	85	Run a risk Ratio (M‐H, Fixed, 95% CI)	0.36 [0.01, 8.53]
8 Neonatal resuscitation	1	85	Risk Ratio (1000‐H, Stock-still, 95% CI)	0.92 [0.34, 2.51]
nine Neonatal encephalopathy	0	0	Take a chance Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
x Serious neonatal morbidity or death	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
11 Childhood disability	0	0	Risk Ratio (G‐H, Stock-still, 95% CI)	0.0 [0.0, 0.0]
12 String arterial blood oxygen content (ml/dl)	1	67	Mean Departure (Four, Fixed, 95% CI)	‐0.80 [‐2.29, 0.69]
13 Cord arterial blood oxygen saturation (%)	1	67	Hateful Departure (IV, Fixed, 95% CI)	‐4.40 [‐11.22, 2.42]

Analysis

Comparison 2 Prophylactic maternal oxygen, Effect i Assisted vaginal delivery.

Assay

Comparison ii Condom maternal oxygen, Outcome 2 Caesarean section.

Analysis

Comparison 2 Prophylactic maternal oxygen, Consequence iv Abnormal fetal center rate tracing.

Analysis

Comparison 2 Safety maternal oxygen, Outcome v String arterial pH < 7.2.

Analysis

Comparison two Condom maternal oxygen, Upshot vi Apgar score < 7 at i minute.

Assay

Comparing 2 Prophylactic maternal oxygen, Issue 7 Apgar score < 7 at v minutes.

Assay

Comparison two Prophylactic maternal oxygen, Event eight Neonatal resuscitation.

Analysis

Comparison 2 Prophylactic maternal oxygen, Effect 12 Cord arterial blood oxygen content (ml/dl).

Analysis

Comparing 2 Safety maternal oxygen, Outcome 13 Cord arterial claret oxygen saturation (%).

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Methods	"Prospective randomization". Method of randomization was non stated.
Participants	Inclusion criteria: women with normal labour in the 2d stage.
Interventions	Maternal oxygen administration throughout the 2nd stage compared with no oxygen.
Outcomes	Umbilical string arterial blood pH. Conclusion: oxygen assistants during normal labour has no consequence on fetal acid‐base of operations status, prolonged utilize of oxygen did not result in deterioration of fetal blood gas values.
Notes	Bangkok, Thailand. 80 women in handling group compared with eighty controls. Abstract study only. Authors to be contacted.
Risk of bias
Bias	Authors' judgement	Back up for judgement
Allotment concealment	Unclear risk	Unclear

Methods	Randomization by sealed envelopes.
Participants	Inclusion criteria: spontaneous or induced labour at term; normal labour at the onset of second stage. Exclusion criteria: respiratory disease; diabetes; hypertension; pre‐eclampsia; meaning fetal heart rate abnormalities.
Interventions	Maternal oxygen administration with face mask at flow charge per unit of 10 L/minute, compared with no oxygen assistants.
Outcomes	Umbilical cord arterial blood gas measurement; Apgar score < seven at i minute; Apgar score < seven at 5 minutes; infants requiring resuscitation.
Notes	Kansas Urban center, Missouri, United states of america. 86 women were randomized into the study: 44 in the command group and 42 in the treatment group. One adult female randomized to receive oxygen administration excluded considering she was inappropriately randomized at 8 cm and required caesarean section before reaching full cervical dilation. Significantly fewer women in the oxygenation group had received narcotic analgesia lone (12% versus 41%, P < 0.05). Epidural analgesia had been used in 71% versus 48% respectively. Caesarean section was performed in 2% and 5% respectively, for dystocia, and vacuum delivery in ii% of each group. Of 39 women assessed for compliance, 27 had perfect compliance, 6 had lxxx%, iv had fifty‐70% and 2 kept the mask on for 30‐38% of the 2d phase.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment	Unclear risk	Unclear

Characteristics of excluded studies [ordered past study ID]

Study	Reason for exclusion
Jozwik 2000	Excluded considering report was not randomized. Methods: prospective selection (non‐randomized) of patients. Inclusion criteria: women with normal singleton term pregnancy in labour or scheduled for elective caesarean section. Mothers should be gratuitous from disease of the respiratory system, diabetes and hypertension. Outset stage of labour should not last for more than 12 hours. Women should not be on fertility drug before pregnancy. For constituent caesarean section, fetal lie must exist longitudinal and Apgar score after 5 minutes should exist matured (maximal). Interventions: maternal oxygen assistants with face mask in 2nd phase of labour, or women scheduled for elective caesarean section given 60% oxygen at 15 Fifty/min for xv minutes. Amazement induced with Iv Thiopental 350 mg and maintained with Isoflurane at minimum alveolar concentration (MAC) 0.viii% and N2O/O2 ratio of 4:two in study subjects. Induction was done with normal anaesthetic gases in controls. Outcome measures: umbilical cord arterial and venous blood gas measurement. Results: for second stage of labour, 17 women given oxygen compared with 343 controls. 24 women scheduled for elective caesarean section given oxygen were compared with 116 controls. Conclusion: oxygen supplementation for 15 minutes during the second stage of labour or in women undergoing elective caesarean department has no meaningful influence on acrid‐base status and values of blood gases.
Lawes 1988	Excluded because did not meet inclusion criteria. 35 women undergoing caesarean section under general amazement were allocated randomly to breathe a mixture with either 50% or 33% oxygen. Mean values for umbilical venous blood were: PO2 3.9 kPa and 3.7 kPa; PCO2 6.2 kPa and 6.ii kPa; pH 7.xxx and 7.31 (50% and 33% groups, respectively, P > 0.05). No differences were found between groups for 1‐ or 5‐ infinitesimal Apgar scores.
Nesterenko 2012	Excluded because did not meet inclusion criteria. Randomized, double‐blind, controlled trial determined the biological and clinical effects of oxygen administration to women in labour for at least 30 minutes before delivery. Participants were 56 women with uncomplicated term pregnancies. Report outcomes were concentrations of superoxide dismutase (SOD) and glutathione (GSSG) in maternal and umbilical cord claret. Maternal and umbilical string blood concentrations of SOD and GSSG did non differ betwixt the two groups at baseline and later delivery.
Simpson 2005	Excluded because evaluation of the effects of maternal oxygen assistants was not by randomized design. Methods: prospective evaluation of the efficacy of intrauterine resuscitation techniques on FSpO2. Inclusion criteria: healthy nulliparous women with singleton fetus in cephalic presentation undergoing induction of labour with oxytocin, having epidural anaesthesia and with reassuring fetal centre rate pattern at the time of enrollment. Mothers should be free of medical or obstetric complication or history of smoking, asthma, chronic or acute pulmonary or cardiac disease. Interventions: starting time stage ‐ randomized comparison of 500 ml or m ml IV fluid bolus of lactated Ringers solution over a twenty‐minute catamenia for pre‐epidural hydration with woman in left lateral position 15 minutes prior to IV fluid bolus, during the bolus and 15 minutes afterwards the bolus was completed. Second phase: randomized evaluation of the effects of maternal position sequence (supine with the head of the bed elevated 30 degrees, left lateral and right lateral) on FSpO2. Third phase: non‐randomized evaluation of the furnishings of maternal oxygen administration (x Fifty/min). Outcome measures: FSpO2, 1‐minute Apgar score, 5‐infinitesimal‐Apgar score. Results: 42 women were randomized in the trial of the consequence of Four fluid while 51 women were randomized for the evaluation of the effect of position sequences. 49 women received oxygen at 10 L/min. This was not a randomized evaluation. Four fluid bolus of 1 000 ml had a greater effect on FSpO2 than IV bolus of 500 ml. Fetal oxygen saturation was higher in the lateral position. Oxygen administration increased FSpO2. The effect persisted for more than than thirty minutes after oxygen was discontinued.

Contributions of authors

GJ Hofmeyr prepared the original version of the review. B Fawole updated the review in June 2003 and 2012, and has primary responsibility for maintaining the review.

Sources of support

Internal sources

• University of the Witwatersrand (GJ Hofmeyr), South Africa.

• The Harold Katz Fund, Academy of the Witwatersrand (GJ Hofmeyr), South Africa.

External sources

• South African Medical Enquiry Council (GJ Hofmeyr), South Africa.

• The Nuffield Provincial Hospitals Trust, London (GJ Hofmeyr), Uk.

• HRP‐UNDP/UNFPA/WHO/World Bank Special Program in Human Reproduction, Geneva (B Fawole), Switzerland.

Declarations of involvement

None known.

References

References to studies included in this review

Sirimai 1997 {published data only}

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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7045413/

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