North American Registry of Midwives (NARM) Practice Exam

At what point in labor are membranes most likely to rupture?

1. Beginning of the second stage

2. End of first stage

3. During transition phase

4. Active labor

The correct answer is: End of first stage

Membrane rupture, commonly known as "water breaking," is most prevalent at the end of the first stage of labor, which encompasses the period of cervical dilation until it is fully dilated at 10 centimeters. During this stage, the cervix softens and gradually opens in response to uterine contractions. As contractions intensify and frequency increases, the tension on the membranes also increases, making rupture more likely. At the end of the first stage, as the baby's head moves lower into the birth canal and pressure builds against the amniotic sac, it's common for membranes to rupture, either with a sudden release of fluid or a gradual leak. This phenomenon is biologically programmed to support the birthing process, providing crucial information regarding the timing and management of labor. While membranes can rupture at other points during labor, such as early in the second stage or during transition, the statistical norm places the end of the first stage as the most frequent occurrence. Active labor and transition refer to phases within the first stage, but the transition phase is characterized more by rapid cervical changes rather than a typical high incidence of membrane rupture.