Role of Maternal Anogenital Distance Measurement in Prediction of Perineal Tears during Vaginal Delivery: A Prospective Cohort Study

Abstract

Introduction: Almost 85% of women suffer from perineal trauma during vaginal birth, which can have long-term consequences. Anogenital Distance (AGD) is a novel and useful parameter for predicting perineal tears during vaginal delivery. Aim: To determine the accuracy and cut-off values of AGD in predicting ≥2nd degree perineal tears. Materials and Methods: A prospective cohort study was conducted in the Department of Obstetrics and Gynaecology at GTB Hospital, New Delhi, India, from January 2021 to April 2022, including 80 patients in group 1 and 80 in group 2. Group 1 consisted of patients who experienced ≥2nd degree perineal tears during vaginal delivery, while group 2 included patients with an intact perineum or up to 1st degree tears. Anthropometric data such as Anus to Clitoris Distance (AGDac) and Anus to Fourchette Distance (AGDaf) (anus to fourchette distance), as well as labour parameters like foetal position, duration of the second stage, induction of labour and birth weight, were noted. Receiver Operating Curves (ROC) were plotted to obtain cut-off values for AGDac and AGDaf in predicting ≥2st degree perineal tears. Unpaired t-tests and Chi-square tests were used to compare quantitative and qualitative parameters, respectively. Results: The mean AGDac (75.99 vs. 77.05) and AGDaf (33.50 vs. 34.52) were lower in group 1 compared to group 2. AGDaf (75%) showed better sensitivity for predicting ≥2st degree perineal tears and anal sphincter injury compared to AGDac (60%). The specificity of AGDaf (55%) was better for predicting ≥2st degree perineal tears, while AGDac (51%) was more specific for sphincter injury. Foetal head position (p=0.016) and birth weight (p=0.002) were identified as the strongest risk factors for tears. Group 1 patients reported more bowel (25% vs. 10%) and prolapse symptoms (11.5% vs. 3.75%) compared to group 2 patients at six weeks postpartum. Conclusion: Perineal length, as measured antenatally by AGD (both AGDac and AGDaf), is useful in predicting the occurrence of perineal tears during vaginal delivery. If found to be short, obstetricians can exercise greater caution during delivery, potentially reducing the incidence of anal sphincter injuries and their long-term consequences.

Keywords

• anus to clitoris
• anus to fourchette
• anal sphincter
• episiotomy