Physiologic childbirth and active management of the third stage of labor : A latent class model of risk for postpartum hemorrhage

Background
Postpartum hemorrhage (PPH) is a threat to maternal mortality worldwide. Evidence supports active management of third stage labor (AMTSL) for preventing PPH. However, trials of AMTSL include women at varying risk levels, such as women undergoing physiologic labor and those with labor complications. Counseling women about their risk for PPH and AMTSL is difficult as many women who appear low-risk can still have PPH.

Methods
This study uses outcomes of 2322 vaginal births from a hospital midwifery service in the United States to examine risks for PPH and effectiveness of AMTSL. Using a latent class analysis approach, physiologic birth practices and other risk factors for PPH were analyzed to understand if discrete classes of clinical characteristics would emerge. The effect of AMTSL on the PPH outcome was also considered by class.

Results
A four-class solution best fit the data; each class was clinically distinct. The two largest Classes (A and B) represented women with term births and lower average parity, with higher rates of nulliparity in Class B. Class A women had more physiologic birth elements and less labor induction or labor dysfunction compared with Class B. PPH and AMTSL use was higher in Class B. In Class B, AMTSL lowered risk for PPH. However, in Class A, AMTSL was associated with higher risk for PPH and delayed placental delivery (>30 minutes).

Discussion
AMTSL may not be as beneficial to women undergoing physiologic birth. Further study of the etiology of PPH in these women is indicated to inform preventive care.