The association between sonographic fetal head circumference, obstetric anal sphincter injury and mode of delivery: A retrospective cohort study

A pre-post implementation study of a care bundle to reduce perineal trauma in unassisted births conducted by midwives

PROBLEM

The perineal-bundle is a complex intervention widely implemented in Australian maternity care facilities.

BACKGROUND

Most bundle components have limited or conflicting evidence and the implementation required many midwives to change their usual practice for preventing perineal trauma.

AIM

To measure the effect of perineal bundle implementation on perineal injury for women having unassisted births with midwives.

METHODS

A retrospective pre-post implementation study design to determine rates of second degree, severe perineal trauma, and episiotomy. Women who had an unassisted, singleton, cephalic vaginal birth at term between two time periods: January 2011 - November 2017 and August 2018 - August 2020 with a midwife or midwifery student accoucheur. We conducted logistic regression on the primary outcomes to control for confounding variables.

FINDINGS

data from 20,155 births (pre-implementation) and 6273 (post-implementation) were analysed. After implementation, no significant difference in likelihood of severe perineal trauma was demonstrated (aOR 0.86, 95% CI 0.71-1.04, p = 0.124). Nulliparous women were more likely to receive an episiotomy (aOR 1.49 95% CI 1.31-1.70 p < 0.001) and multiparous women to suffer a second degree tear (aOR 1.18 95% CI 1.09-1.27 p < 0.001).

DISCUSSION

This study adds to the growing body of literature which suggests a number of bundle components are ineffective, and some potentially harmful. Why, and how, the bundle was introduced at scale without a research framework to test efficacy and safety is a key concern.

CONCLUSION

Suitably designed trials should be undertaken on all proposed individual or grouped perineal protection strategies prior to broad adoption.

Factors associated with spontaneous vaginal birth in nulliparous women: A descriptive systematic review

PROBLEM

Spontaneous vaginal birth (SVB) rates for nulliparous women are declining internationally.

BACKGROUND

There is inadequate understanding of factors affecting this trend overall and limited large-scale responses to improve women's opportunity to birth spontaneously.

AIM

To undertake a descriptive systematic review identifying factors associated with spontaneous vaginal birth at term, in nulliparous women with a singleton pregnancy.

METHODS

Quantitative studies of all designs, of nulliparous women with a singleton pregnancy and cephalic presentation, who experienced a SVB at term were included. Nine databases were searched (inception to October 2022). Two reviewers undertook quality appraisal; Randomised Controlled Trials (RCTs) with high risk of bias (ROB 2.0) and other designs with (QATSDD) scoring ≤ 50% were excluded.

FINDINGS

Data were abstracted from 90 studies (32 RCTs, 39 cohort, 9 cross-sectional, 4 prevalence, 5 case control, 1 quasi-experimental). SVB rates varied (13%-99%). Modifiable factors associated with SVB included addressing fear of childbirth, low impact antenatal exercise, maternal positioning during second-stage labour and midwifery led care. Complexities arising during pregnancy and regional analgesia were shown to decrease SVB and other interventions, such as routine induction of labour were equivocal.

DISCUSSION

Antenatal preparation (low impact exercise, childbirth education, addressing fear of childbirth) may increase SVB, as does midwifery continuity-of-care. Intrapartum strategies to optimise labour progression emerged as promising areas for further research.

CONCLUSION

Declining SVB rates may be improved through multi-factorial approaches inclusive of maternal, fetal and clinical care domains. However, the variability of SVB rates testifies to the complexity of the issue.

Neonatal head circumference as a risk factor for obstetric anal sphincter injuries: a systematic review and meta-analysis

OBJECTIVE

Between 53% and 79% of women will sustain some degree of perineal laceration during vaginal delivery. Third- and fourth-degree perineal lacerations are known as obstetric anal sphincter injuries. Timely diagnosis and prompt treatment of obstetric anal sphincter injuries can help to prevent the development of severe consequences like fecal incontinence, urinary incontinence, and rectovaginal fistula. Neonatal head circumference is routinely measured postpartum but is often not mentioned as a risk factor for obstetric anal sphincter injuries in clinical guidelines. Thus far, no review article on the risk factors for obstetric anal sphincter injuries has discussed the role of neonatal head circumference. This study aimed to review and analyze the relationship between head circumference and the occurrence of obstetric anal sphincter injuries among previous studies to conclude whether head circumference should be recognized as an important risk factor.

DATA SOURCES

Through study screening on Google Scholar, PubMed, Scopus, and Science Direct for articles published between 2013 to 2023, followed by assessment of eligibility, this study ended up reviewing 25 studies, 17 of which were included in the meta-analysis.

STUDY ELIGIBILITY CRITERIA

Only studies that reported both the neonatal head circumference and the occurrence of obstetric anal sphincter injuries were included in this review.

METHODS

The included studies were appraised using the Dartmouth Library risk of bias assessment checklist. Qualitative synthesis was based on the study population, findings, adjusted confounding factors, and suggested causative links in each study. Quantitative synthesis was conducted using calculation and pooling of odds ratios and inverse variance using Review Manager 5.4.1.

RESULTS

A statistically significant association between head circumference and obstetric anal sphincter injuries was reported in 21 of 25 studies; 4 studies reported that head circumference was a true independent risk factor. A meta-analysis of the studies that reported neonatal head circumference as a dichotomous categorical variable with a cutoff point of 35±1 cm yielded statistically significant pooled results (odds ratio, 1.92; 95% confidence interval, 1.80-2.04).

CONCLUSION

The risk for obstetric anal sphincter injuries increased as the neonatal head circumference increased-this should be considered in decision-making during labor and postpartum management to attain the best outcome.

Birthweight difference between deliveries and the risk of obstetric anal sphincter injury in parous women

INTRODUCTION AND HYPOTHESIS

While obstetric anal sphincter injury (OASI) is less frequent in parous compared to nulliparous women, it remains a major concern affecting quality of life of women worldwide. The aim of this study was to evaluate the association between birthweight (BW) difference between deliveries and risk of OASI in parous women.

METHODS

We performed a retrospective case-control study including parous women with at least one previous vaginal delivery who were diagnosed with OASI. The control group consisted of parous women who did not have OASI during vaginal delivery. Controls were matched in a 1:2 ratio by year of birth, maternal age, and parity. Medical history, obstetric background, and current labor-related data were compared. Further univariate and multivariable analyses were performed, assessing for risk factors for OASI.

RESULTS

One hundred eight parous women who had a diagnosis of OASI and a control group of 216 parturients who delivered without OASI were included in the final analysis. Differences between the current BW and the preceding and maximal previous BW were evaluated. There were significantly higher rates of women who had a larger neonate with > 500 g difference between the current and previous BW in the OASI group than in those with no OASI (28.7% vs. 12.30%, respectively; p < 0.001). Following a multivariable analysis for the dependent parameter of OASI, the following parameters were found to be independently associated with OASI outcome: previous operative vaginal delivery, BW ≥ 90th percentile, and current BW ≥ 500 g compared to previous maximal BW.

CONCLUSIONS

In parous women, neonatal BW increase between deliveries of > 500 g is associated with OASI.

Can sonographic fetal head circumference measurement help predict Obstetric Anal Sphincter Injury?

OBJECTIVE

Obstetric Anal Sphincter Injuries (OASIS) occur in 2 to 19% of vaginal deliveries in the United States. Neonatal parameters such as birthweight above 4000g or neonatal head circumference above 37 cm are known risk factors for OASIS. We hypothesized that sonographic fetal Head Circumference (sfHC) size assessed by ultrasound antenatally could help predict OASIS.

METHODS

This study is a retrospective cohort study between 2005 and 2016. Antenatal ultrasound Head Circumference (sfHC) assessment, maternal demographics, and labor and delivery data were abstracted and compared in women with and without OASIS.

RESULTS

Of 2057 pregnant women that had sfHC assessment, 121 (5.8%) had OASIS. In the unadjusted analysis, sfHC above the 90^th percentile was associated with OASIS OR 1.12 (1.02-1.23) p=0.015. When adjusted for gestational age at delivery, maternal age, race, prolonged 2^nd stage, BMI, infant gender, and intrapartum oxytocin use, sfHC above the 90^th percentile remained significantly associated with OASIS (OR=1.13, 95% CI 1.00-1.27, p=0.050).

CONCLUSION

In our cohort, sfHC above the 90^th percentile was associated with a greater risk of OASIS. As OASIS significantly impacts short and long-term health outcomes such as perineal pain, dyspareunia, urinary and fecal incontinence, sfHC could be an additional antenatal marker to help clinicians counsel pregnant women about the risk of OASIS.