The role of fetal head circumference in the formation of obstetric anal sphincter injuries following vacuum deliveries among primiparous women

Predelivery sonographic predictors of obstetric anal sphincter injury among nulliparous women

OBJECTIVE

Data available at admission to delivery of nulliparous has rarely been investigated for prediction of obstetric anal sphincter injury (OASI). The aim of the present study was to study risk factors for OASI in nulliparous based on information available at admission.

METHODS

A retrospective study of all nulliparous women undergoing labor, during March 2011 to January 2021 was performed. We compared women with OASI following delivery to those without by univariate and multivariable regression.

RESULTS

A total of 30 262 deliveries were included and 4181 (13.4%) of those were delivered by an emergent cesarean delivery. OASI followed 453 (1.5%) deliveries. Women in the OASI group were younger 29 ± 4.4 versus 30 ± 4.8, P = 0.001. In a multivariable regression analysis, higher sonographic estimated fetal weight was positively associated with OASI occurrence (aOR, 95% CI: 1.13 [1.00-1.29]). Maternal age was inversely associated with OASI occurrence (adjusted odds ratio [aOR], 95% confidence interval [CI] 0.95 [0.92-0.97]).

CONCLUSION

Sonographic fetal weight estimation is an independent risk factor for OASI occurrence that may be available at admission for delivery among nulliparous women.

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.

A dynamic prediction score for obstetric anal sphincter injury among nulliparous women delivering vaginally

OBJECTIVE

To develop a risk score for obstetric anal sphincter injury (OASI) occurrence among nulliparous women delivering vaginally, based on data available at admission for delivery and as labor progresses.

METHODS

A retrospective study of all nulliparous women who delivered vaginally between March 2011 and January 2021. Characteristics were compared between OASI and no-OASI groups. Multivariable analyses were performed to identify independent risk factors for OASI occurrence.

RESULTS

OASI occurred in 453 (1.7%) of 26 081 women who met the inclusion criteria. The following variables were independently associated with OASI: maternal height (adjusted odds ratio [aOR] 0.97, 95% confidence interval (CI) 0.95-0.99), hypertensive disorders (aOR 1.74, 95% CI 1.03-2.95), sonographic fetal weight estimation (aOR 1.00, 95% CI 1.00-1.00), second-stage duration (aOR 1.00, 95% CI 1.00-1.00), occiput posterior position (aOR 2.87, 95% CI 1.79-4.62), and episiotomy performance (aOR 0.63, 95% CI 0.47-0.84). In a risk score based on variables available at admission for delivery, the presence of two factors was associated with 4.3% OASI risk. Upon incorporating intrapartum variables, the presence of two risk factors was associated with 2.9% OASI rate.

CONCLUSION

A dynamic risk score for OASI occurrence based on data available at admission for delivery and as delivery progresses can assist in counseling regarding OASI risk. A dynamic risk score for obstetric anal sphincter injury occurrence based on data available at admission for delivery and intrapartum was developed.

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

BACKGROUND

There is no consensus to the implications of an increased sonographic fetal head circumference (HC) and its impact on delivery.

AIM

To examine if there is any association between sonographic fetal HC, obstetric anal sphincter injury (OASIS) and mode of delivery.

MATERIALS AND METHODS

A retrospective cohort study of term, singleton births between April 2017 and March 2019 at a large regional hospital in Australia with a third trimester ultrasound. Logistic regressions were performed investigating sonographic fetal HC and additional risk factors for OASIS. Further multinomial logistic regressions assessed the relationship between the sonographic HC and mode of delivery. Odds ratios and their 95% CIs were reported.

RESULTS

Of 667 eligible women, 487 (73%) had vaginal births, with 32 (6.6%) sustaining an OASIS and 180 (27%) had caesarean sections (CS). The sonographic fetal HC did not show an association with OASIS (odds ratio 1.005; CI 0.99-1.01, P = 0.447). A statistically significant association (P < 0.05) with OASIS was found with Asian ethnicity (4.38; 1.5-11.32), prolonged second stage (≥2 h) (4.26; 1.57-10.49) and occiput posterior position (4.01; 1.08-11.92). For women with a sonographic fetal HC ≥ 90th percentile, the odds of having CS compared to a spontaneous vaginal birth are 2.77 (95% CI: 1.36, 5.62; P = 0.005) times higher than those who have a HC < 90th percentile.

CONCLUSION

This study does not support the use of sonographic fetal HC in assessing a woman's risk of sustaining an OASIS. Sonographic fetal HC is associated with mode of delivery.

The role of sonographic head circumference in the occurrence of subgaleal hemorrhage following vacuum delivery

OBJECTIVE

Subgaleal hemorrhage (SGH) is a severe neonatal morbidity that is associated with vacuum-assisted delivery (VAD). Large sonographic head circumference (sHC) was previously associated with complicated VAD. Nevertheless, the association of large sHC with SGH formation following VAD is underreported. We aim to evaluate the role of sonographic head circumference (sHC) with SGH formation following attempted VAD.

METHODS

A retrospective case-control study. Cases comprised singleton pregnancies for whom attempted VAD resulted in SGH with an sHC measured within 2 weeks from delivery. Controls were VAD deliveries which not resulted in SGH, with an sHC measured within 2 weeks from delivery. We matched controls in a 1:1 ratio by gestational age, parity and year of delivery.

RESULTS

Overall, 118 women were included in the SGH study group and were matched to 118 controls. Baseline maternal and fetal characteristics were similar between the groups except for higher neonatal birth weight in the SGH group (median 3422 vs. 3195 grams, p = .001). sHC did not vary between groups (median 336 mm in SGH groups vs. 333, p = .08). Rate of sHC >90th and >95th percentile did not significantly differ between the groups (13.6% vs. 8.5%, 6.8% vs. 3.4%, p = .21, p = .37, for SGH vs. controls, respectively). In multivariate regression analysis, sHC was not found to be independently associated with SGH - aOR (95% CI) 1.004 (0.97-1.03). Receiver operating characteristic curves of sHC for SGH formation underlined an area under the curve of 0.58 (95% CI) (0.51-0.65).

CONCLUSIONS

sHC is not associated with SGH formation following VAD.

The association between vacuum-assisted vaginal delivery and anal sphincter injury

INTRODUCTION

Vacuum-assisted vaginal delivery (VAVD) is considered a major risk factor for obstetric anal sphincter injuries (OASIS). However, it is difficult to estimate its true contribution to the occurrence of OASIS, as its performance may be confounded by other determinants. Therefore, we aimed to evaluate the association of VAVD with OASIS among primiparous women compared to SVD.

METHODS

A retrospective cohort study including all primiparous women who vaginally delivered a cephalic singleton gestation during the years 2011 to 2020. As VAVDs were not performed before 34 gestational weeks, we capped the cohort at this gestational age. Women were allocated into two groups: VAVDs and spontaneous vaginal deliveries (SVD). We compared women with OASIS to those without and performed a multivariate analysis including factors that were found significant in the univariate analysis. We further divided the whole cohort into different subcategories. The primary outcome was the rate of OASIS in VAVD compared to SVD.

RESULTS

Overall, 23,272 primiparous vaginal deliveries were available for evaluation. Of these, 3595 delivered by VAVD and 19,677 delivered spontaneously. OASIS occurred in 421 (1.8%) of the deliveries. OASIS were more common in VAVDs than in SVDs [83 (2.3%) vs. 338 (1.7%), respectively, OR (95% CI) 1.35 (1.06-1.72), p = 0.01]. After multivariate regression analysis, OASIS were not found to be independently associated with the mode of delivery [aOR 1.21 (95% CI) 0.88-1.68, P = 0.23]. In a categorical analysis of OASIS rates by risk factors and mode of delivery, VAVD was not associated with an increase in OASIS among women giving birth to neonates weighing > 3500 g compared to SVD [OR (95% CI) 1.02 (0.65-1.62), P = 0.90].

CONCLUSION

Among primiparous women VAVD did not increase the risk of OASIS compared to SVD.

Risk factors for obstetric anal sphincter injury among parous women

PURPOSE

Nulliparity and operative vaginal delivery are established risk factor for obstetric anal sphincter injury (OASI). However, risk factors for OASIS occurrence among parous women delivering vaginally are not well-established. We aimed to study the risk factors for OASI occurrence among parous women.

METHODS

A retrospective study including all parous women who delivered vaginally at term during 2011-2019 at a university hospital. Deliveries of parous women with OASI were compared to deliveries without OASI. The risk factors associated with OASI were investigated.

RESULTS

Overall, 35,397 women were included in the study with an OASI rate of 0.4% (n = 144). A higher rate of only one previous vaginal delivery was noted in the OASI group (78.5% vs. 46.4%, OR [95% CI] 4.20, 2.82-6.25, p < 0.001). The rate of vacuum-assisted deliveries was comparable between the study groups. The median birth weight was higher among the OASI group (3566 vs. 3300 g, p < 0.001), as was the rate of macrosomic neonates (19.4% vs. 5.5%, OR [95% CI] 4.15, 2.74-6.29, p < 0.001). On multivariate logistic regression analysis, only two factors were independently positively associated with the occurrence of OASI: a history of only one previous vaginal delivery (adjusted OR [95% CI] 4.34, 2.90-6.49, p = 0.001), and neonatal birth-weight (for each 500 g increment) (adjusted OR [95% CI] 2.51, 1.84-3.44, p < 0.001).

CONCLUSIONS

Among parous women, the only factors found to be independently positively associated with OASI were the order of parity and neonatal birth-weight. Vacuum-assisted delivery was not associated with an increased risk of OASI among parous women.