This large study examined nearly 478,000 women who attempted a vaginal birth after a previous C-section. The researchers used data from the Centers for Disease Control and Prevention covering births from 2020 to 2024. They applied a cumulative risk score ranging from -1 to 7 points, based on factors like BMI, diabetes, high blood pressure, and maternal age.
The main finding was a consistent pattern: as the risk score increased, the chance of a successful vaginal birth decreased. For example, a score of -1 linked to a 90.5% success rate, while a score of 4 or higher linked to a 44.8% success rate. Similarly, the risk of a newborn needing NICU care rose steadily with higher scores.
Among individual factors, having had a prior vaginal delivery was the strongest predictor of success, linked to an 86.4% success rate compared to 62.5% for those without one. The study also found that the number of providers performing these births remained stable during the observation period. Readers should understand that this tool helps predict outcomes for counseling but does not change the underlying risks associated with the health conditions included in the score.