New Method Paves the Way for Fewer Serious Birth Injuries

According to a study by the University of Gothenburg, high birth weight is the main risk factor for birth injuries to the anal sphincter muscles in women giving birth. This new method of predicting risks could improve care and reduce injuries.

Five percent of all women giving birth to their first child in Sweden suffer birth injuries in the form of obstetric anal sphincter injuries (OASI), which affect the muscles responsible for controlling gas and bowel movements. These injuries can lead to long-term problems and affect both physical health and quality of life. The aim of this study, published in the Journal of Clinical Epidemiology, was to develop and validate a predictive model that can assess the risk of such a condition before vaginal delivery. The study is based on registry data from all 45 maternity facilities in Sweden for the period 2009 to 2017. A total of around 600,000 singleton births with cephalic presentation, the most common form of delivery, were examined.

Larger Babies Increased the Risk the Most

Prediction models were developed for three common birth scenarios: first vaginal birth, vaginal birth after cesarean section, and second vaginal birth. A variety of risk factors were taken into account, such as the baby’s birth weight, obstetric assistance with, for example, a vacuum extractor, the size and age of the mother, and previous anal sphincter injuries. The baby’s birth weight proved to be the strongest predictor of OASI in all birth scenarios – larger babies increased the risk of severe vaginal tears. In women who gave birth to their second child vaginally, a previous anal sphincter injury was a strong indicator of a repeat injury. A third risk factor was the use of a vacuum extractor.

The prediction model for women giving birth vaginally for the second time was the most accurate, followed by the models for first vaginal birth and vaginal birth after a cesarean section. However, the reliability of all three models was comparable to similar and established prediction tools used in other areas such as cardiovascular disease and breast cancer.

Tool for Assessing the Risk of Severe Birth Injuries

The lead author of the study is Jennie Larsudd-Kåverud, PhD student in obstetrics and gynecology at the University of Gothenburg and obstetrician at Sahlgrenska University Hospital: “The statistical models used in this study enabled us to distinguish at-risk individuals at the same level as other prediction models currently widely used in healthcare,” she explains.

Until now, there has been no clinically used tool that can predict the risk of OASI during childbirth as accurately as this newly developed calculator. The aim is to reduce the number of injuries through timely and appropriate measures. According to the researchers, the models developed provide both medical professionals and pregnant women with a tool for assessing the risk of severe birth injuries. If the risk is low, concerns can be alleviated. If the risk is higher, there is an opportunity for more careful joint planning and prevention.