Fetal malposition in labour and health outcomes for women and their newborn infants: A retrospective cohort study

Introduction Occiput-posterior (OP) or occiput-transverse (OT) fetal malposition has a prevalence of 33–58% in the first-stage of labour with 12–22% persisting until delivery. Malposition is associated with significant maternal and neonatal morbidity. Most previous studies report the incidence and adverse maternal and fetal outcomes of persistent fetal malposition in the second stage of labour and do not include outcomes that may be present in the first stage of labour. Aims To assess the incidence and health outcomes for women and their newborn infants of a fetal malposition in the first or second stage of labour. Materials and methods A retrospective cohort study of 738 maternity records (randomly selected) from a tertiary hospital in New Zealand. Maternal and neonatal characteristics are described. Outcomes for women with a fetus in an OP or OT position in labour are compared to those for women with a fetus in an occiput-anterior position (OA). Results 499 (68%) women had an OP/OT positioned fetus and 239 (32%) had an OA positioned fetus on vaginal examination in labour. Women had similar characteristics except a body mass index ≥30 kg/m2 was more common in the OP/OT group. Fetal malposition appears to be more likely in women with a right-sided fetal occiput. Three quarters of OP/OT fetuses rotated anteriorly by birth. Fetal malposition compared to no malposition was associated with oxytocin augmentation, epidural use, a longer first stage of labour, fewer normal vaginal births, and more caesarean sections. Fetal malposition during labour was not associated with adverse neonatal outcomes. Conclusion Interventions such as maternal posture in the first and second stage of labour could potentially reduce the incidence of malposition and improve health outcomes for mothers.

the sample collected from? What is the reason for using a threshold of ≥6? Provide a reference to support the choice of this threshold. Explain the reason for not using fetal umbilical artery cord pH <7.0, and or base deficit ≥12 mmol/L.
Response: The sample for cord lactate levels were collected from umbilical arterial vessels. The phrase 'cord lactate' has been replaced with 'umbilical arterial lactate' in line 73. In addition, the revised wording has been applied to the Results section (lines 202 -203) and Table 4. The sentence 'Abnormal arterial cord lactates, considered a more accurate measure of metabolic acidosis than umbilical artery pH <7.0 and Base Excess <-12 mmol/l alone, were the standard measure of fetal acidosis at the hospital in 2018 with a clinical cutoff of ≥ 6 mmol/l, though revised to ≥ 6.1 mmol/l in 2019 [26].' has been added including the reference, in lines 77 -79.
14. Methods and materials: Provide additional details about sample size calculation. What formular/software was used for the sample size calculation? What were the input parameters?
Response: 'ClinCalc.com' was the software used for sample size calculations, this detail has been added to line 84. The input parameters are provided in line 85 i.e. a 16% incidence of caesarean section in the OP/OT group and a 10% incidence in the OA group with an accompanying citation for Akmal et al 2004 BJOG. 15. It is written in the manuscript that 1000 was the sample size (as documented in the section on methods and materials). In the abstract, the authors wrote that only 738 maternity records were randomly selected (see abstract). Provide details about the random selection. If necessary include a flow diagram to make it easier to understand. Clarify if there were exclusion criteria. Response: Details about the random selection of records have been moved from the Results to the Methods and Materials of the main text. Exclusion criteria are described in lines 56-57 of the Methods and Materials i.e. 'Women with a major fetal abnormality were not included'.
16. Clarify the reason for reporting relative risk in this retrospective study. Justify your answer with appropriate reference/s. Response: The following sentence has been added to the Results section 'Overall, 18% of fetuses Response: Thank you, we do understand why the wording might be confusing. While studies discussed in the paper by Martino et al have reported on outcomes during the first and second stage of labour, the fetal malposition was determined at birth or in the second stage of labour, and therefore may not reflect women who had a fetal malposition in the first stage before anterior fetal rotation. The studies by Neri et al (1995) and Gardberg et al (1994) report on outcomes of persistent malposition that was diagnosed in the second stage of labour. There is a paucity of evidence which dates back 20 years reporting outcomes related to malposition during the first stage as mentioned in the background (lines 42 -44) referring to duration of labour and caesarean section. In light of your feedback, the sentence has been rephrased as 'A strength of this study is the novel approach of assessing outcomes related to malposition that is diagnosed during first and second stage labour rather than only a persistent OP/OT in the second stage labour or at birth,' (lines 225 -227).
35. Discussion, third paragraph, sentence: "Data were sometimes not available for some of the study outcomes due to an absence of documentation in the medical records." Explain the reason for not reporting missing data.
Response: To provide further clarity, the following sentence has been added 'While missing data is not reported as a subset category, the denominators reflect the totals minus the missing data.' (lines 243-245).
36. Discussion, seventh paragraph, sentence: "However, in contrast, this study saw an increased use of oxytocin to augment labour after excluding IOL,…" "Excluding IOL" is difficult to understand. Revise the sentence.
Response: The sentence has been revised to "…after excluding women who had an induction of labour.' (line 265).
37. What is the explanation for the fewer postnatal catheterisations that were performed for women in the OP/OT group (9.6% cf.14.6% OA, P=0.043).
Response: The following sentence has been added 'It is not clear why there were fewer postnatal urinary catheterisations in the OP/OT group.' (lines 284 -285). 38. Are there measures to prevent OP position. Response: The last sentence has been revised to 'In addition, further research exploring effective maternal posture interventions and the impact of gravity on the fetal spine to correct sonographically confirmed fetal malposition during labour [34] could lead to significant improvements in maternal health.' (lines 295 -298).

Abstract:
The conclusion sentence does not match the aims sentence and should be re-written.
Response: We have revised the Conclusion to read 'Interventions such as maternal posture in the first and second stage of labour could potentially reduce the incidence of malposition and improve health outcomes for mothers.' (lines 20-22).

Introduction:
Why did the authors decide to include 2 nd stage malposition?
Response: We considered it important to have evidence of the incidences and outcomes of malposition at any time in labour so that the full extent of malposition on a continuum is reflected in a single sample, given that an occipito-anterior fetus may become an occipito-posterior fetus in the second stage in women with an epidural (Lieberman 2005) and that studies of malposition in the second stage do not reflect labour outcomes such as abnormal fetal heart rate in women who have a caesarean section in the first stage. Therefore, a single study that includes malposition at any stage in labour provides a comprehensive assessment of outcomes of malposition in labour which is comprehensible and useful to trialists, healthcare providers and consumers.

Methods and materials:
Line 57 -consider changing the word 'jiggling' to another word. Did the authors consider comparing 1st stage malposition versus persistent second stage malposition with regards to perinatal outcomes?
Response: A comparison of first stage malposition and persistent second stage malposition was outside the scope of this study which was to compare outcomes for women with OP/OT position to women with OA position. However, the sentence 'Differences in outcomes of malposition in the first stage of labour compared to the second stage could be the subject of further research.' has been added to the section where areas for future research are discussed (lines 294-295).
Were adverse outcomes different between fetuses who were malpositioned in the 1st stage of labor, but then did not persist in the 2nd stage?
Response: This was not within the scope of this study, which was a comparative study of OP/OT and OA fetal positions in a single cohort of women from first stage of labour.

Results:
It is surprising that the length of the second stage of labor did not differ based on malposition.
Why do the authors think that is?
Response: Thank you for drawing this to our attention, the following sentence has been inserted in the Discussion (lines 273-275) 'This likely reflects the 74% rate of anterior fetal rotation in the OP/OT group and that 80% of those with a persistent malposition at birth had a caesarean section, with significantly more caesareans performed in the first stage of labour.' What was the median duration of second stage in both groups?
Response: The median duration of the second stage was 1:10 median hours and minutes OP/OT and 1:05 median hours and minutes for OA. We have added this information in lines 271-272.
What were the indications for operative delivery?
Response: Indications for operative delivery are presented in Table 3 and discussed in the Results.
There was no significant difference between the groups.

Discussion:
The authors not the inaccuracy of digital examination for fetal position. They should add a sentence about how ultrasound confirmation is superior. Perhaps a future study can look at ultrasound verified fetal malposition.
Response: In the Discussion we refer to the inaccuracy of diagnosis by digital examination compared to sonographic diagnosis in lines 233 and 240. The words 'sonographically confirmed' now precede "fetal position" in the last sentence of the Discussion (lines 296-297).

Reviewer #2
Since it is a retrospective study where the data was gathered from the clinical documents, how complete and accurate was the information? in clinical practice, patients are managed by midwives, medical students and doctors of different level of training and experience. Furthermore, handwritings differ and sometimes it might be impossible to read what was written. Under the limitations of this study the authors must add the problems experienced in this respect.
Response: Totals for all outcomes reflect the data that was available for each outcome. The following sentence 'Whilst missing data are not reported as a subset category, the denominators reflect the totals minus the missing data.' has been added, according to the editors comment, to lines 243-244.
Missing data for location of placenta was fairly common due to the number of women under private care who often have their ultrasound scans in the community and the data is not then shared with the hospital. The text ', reflecting those receiving private scans in the community,' has been inserted into the sentence discussing this in the Discussion (lines 260-261). All entries of vaginal examinations in the maternity records at Auckland Hospital are verified by a qualified midwife or performed by obstetric registrars. The Methods and Materials now have the words 'by a midwife or obstetrician' follow the words "vaginal examination" in lines 54-55, as per Reviewer #1's comment. The following sentence has been added to the limitations, 'Though hand-written notes could sometimes be difficult to read on normal settings, they became readable by magnifying the script.' (lines 244-245).
Again, thank you for your very helpful comments.