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.

Risk factors for severe perineal trauma during childbirth: An updated meta-analysis

Several studies have investigated the importance of maternal, fetal factors and intrapartum characteristics in predicting severe perineal lacerations. The purpose of the present systematic review is to accumulate current evidence and provide estimated effect sizes for the various risk factors described. We reviewed Medline, Scopus, Clinicaltrials.gov, EMBASE, Cochrane Central Register of Controlled Trials CENTRAL and Google Scholar for published studies in the field for observational studies as well as randomized controlled trials. Two researchers independently assessed the included studies and documented outcomes. Data extraction was performed using a modified data form that was based in Cochrane`s data collection form for intervention reviews for RCTs and non-RCTs. Forty-three articles were selected for inclusion in the present systematic review. The analyzed population reached 716,031 parturient of whom 22,280 (3,1%) sustained third- and fourth-degree perineal lacerations. Several risk factors were identified. Instrumental delivery [RR 3.38 (2.21, 5.18)], midline episiotomy [RR 2.88 (1.79, 4.65)] and a persistent occiput posterior position [RR 2.73 (2.08, 3.58)] were associated with the higher risk of developing severe perineal lacerations. Mediolateral episiotomy did not increase, but was also not protective against perineal lacerations [RR 1.55 (0.95, 2.53)]. Several factors contribute to the development of severe perineal lacerations. The present meta-analysis presents accumulated data that may help physicians estimate risks and provide appropriate patient counseling.