What are the likelihoods of cesarean section (C-section), failed induction, and successful labor induction after membrane sweeping in primiparous women at 41 weeks of gestation, and what is the risk of intrauterine fetal death (IUFD)?

From the Guidelines

For primiparous women at 41 weeks of gestation, the likelihood of requiring a cesarean section (c-section) is significantly increased, with approximately 30-40% of women undergoing c-section, as induction of labor at 41 weeks was associated with a significantly increased risk of cesarean delivery (RR, 1.39) 1.

Induction of Labor

Inductions of labor after 41 weeks have a higher failure rate, with around 20-30% of inductions failing to progress to vaginal delivery, especially in primiparous women.

• The success rate of membrane sweeps at 41 weeks is around 50-60% in primiparous women, increasing the likelihood of going into labor within 24-48 hours 1.
• However, this procedure may cause discomfort and bleeding.

Risk of Intrauterine Fetal Death (IUFD)

The risk of intrauterine fetal death (IUFD) increases significantly after 41 weeks, with an estimated risk of 2-3 per 1,000 ongoing pregnancies at 41 weeks, and rising to 4-5 per 1,000 by 42 weeks, as fetal death may occur in otherwise uncomplicated pregnancies, but is more likely with recognized risk factors 1.

Recommendations

Given these risks, it is generally recommended that primiparous women at 41 weeks of gestation be closely monitored and consider induction of labor to minimize the risk of IUFD and other complications.

• If induction is attempted, it is typically done using medications such as oxytocin, with or without prostaglandin gel or tablets, and continuous fetal monitoring.
• The decision to induce labor or perform a c-section should be made on a case-by-case basis, taking into account individual risk factors and fetal well-being.

From the Research

Likelihoods of C-Section, Failed Induction, and Successful Labor Induction

• The likelihood of cesarean section (C-section) after membrane sweeping in primiparous women at 41 weeks of gestation is not significantly different from expectant management, with a relative risk of 0.98 [ 2 ].
• The risk of failed induction is not directly reported in the provided studies, but the risk of cesarean delivery is increased with induction of labor, particularly in nulliparous women [ 3 ].
• The likelihood of successful labor induction after membrane sweeping in primiparous women at 41 weeks of gestation is not directly reported in the provided studies, but induction of labor at 41 weeks is associated with a reduced risk of stillbirths and perinatal mortality [ 3 ].

Risk of Intrauterine Fetal Death (IUFD)

• The risk of intrauterine fetal death (IUFD) is reduced with induction of labor at 41 weeks, with an adjusted odds ratio of 0.15 [ 3 ].
• The incidence of potentially gestational age-associated perinatal mortality between 41 and 42 weeks is 0% with induction of labor and 0.16% with expectant management [ 4 ].

Outcomes by Parity

• Nulliparous women have a decreased risk of severe adverse perinatal outcome with induction of labor at 41 weeks, with a relative risk of 0.20 [ 2 ].
• Multiparous women do not have a significant reduction in perinatal mortality or morbidity with induction of labor at 41 weeks [ 2 ].
• Induction of labor at 41 weeks is associated with an increased risk of cesarean section in both nulliparous and multiparous women [ 3 ].