Term Elective Induction of Labor and Pregnancy Outcomes Among Obese Women and Their Offspring

Abstract

Objective: To evaluate whether elective induction of labor between 39 through 41 weeks of gestation, as compared with expectant management, is associated with reduced cesarean delivery and other adverse outcomes among obese women and their offspring.

Methods: We conducted a retrospective cohort study using the 2007-2011 California Linked Patient Discharge Data-Birth Cohort File of 165,975 singleton, cephalic, nonanomalous deliveries to obese women. For each gestational week (39-41), we used multivariable logistic regression models, stratified by parity, to assess whether elective induction of labor or expectant management was associated with lower odds of cesarean delivery and other adverse outcomes.

Results: At 39 and 40 weeks of gestation, cesarean delivery was less common in obese nulliparous women who were electively induced compared with those who were expectantly managed (at 39 weeks of gestation, frequencies were 35.9% vs 41.0%, respectively [P<.05]; adjusted odds ratio [OR] 0.82, 95% CI 0.77-0.88). Severe maternal morbidity was less frequent among electively induced obese nulliparous patients (at 39 weeks of gestation, 5.6% vs 7.6% [P<.05]; adjusted OR 0.75, 95% CI 0.65-0.87). Neonatal intensive care unit admission was less common among electively induced obese nulliparous women (at 39 weeks of gestation, 7.9% vs 10.1% [P<.05]; adjusted OR 0.79, 95% CI 0.70-0.89). Patterns were similar among obese parous women at 39 weeks of gestation (crude frequencies and adjusted ORs [95% CIs] were as follows: for cesarean delivery, 7.0% vs 8.7% [P<.05] and 0.79 [0.73-0.86]; for severe maternal morbidity, 3.3% vs 4.0% [P<.05] and 0.83 [0.74-0.94]; for neonatal intensive care unit admission: 5.3% vs 7.4% [P<.05] and 0.75 [0.68-0.82]). Similarly, elective induction at 40 weeks of gestation was associated with reduced odds of cesarean delivery, maternal morbidity, and neonatal intensive care unit admission among both obese nulliparous and parous patients.

Conclusion: Elective labor induction after 39 weeks of gestation was associated with reduced maternal and neonatal morbidity among obese women. Further prospective investigation is necessary.

Figure 1

The top of this flow chart shows the number of women excluded from our sample due to study ineligibility (eg, BMI less than 30, pre-existing maternal conditions, multiple gestations) or missing data. Numbers of excluded observations do not overlap. The bottom of this flowchart represents the number of obese women analyzed at each gestational week (39 weeks through 41 weeks), stratified by parity. Some of these numbers overlap, because obese women who were expectantly managed at one gestational week could be electively induced at a later week. In each comparison (eg, elective induction at 39 weeks of gestation compared with expectant management), spontaneous and medically indicated deliveries that occurred during the index week were excluded. As a consequence, week-specific counts may not sum to the total number of observations.*Pre-existing medical conditions include chronic hypertension, pre-existing or gestational diabetes, pre-existing cardiac disease, pre-existing renal disease, pre-existing liver or biliary tract disorder, vasa or placental previa, or isoimmunization.

Figure 2

Adjusted odds ratios for elective labor induction, as compared to expectant management, and pregnancy outcomes among obese women. A–K display adjusted odds ratios, stratified by parity, for elective induction of labor (compared with expectant management) and pregnancy outcomes among obese women and their offspring. Models were adjusted for maternal age, education, and race and ethnicity; first-trimester prenatal care initiation; payment source for delivery; birth year; obesity class; and delivery at a teaching hospital. Cesarean delivery (A), operative vaginal delivery* (B), severe maternal morbidity^† (C), infant death^‡ (D), neonatal intensive care unit (NICU) admission^§ (E), macrosomia (≥4,500 g) (F), chorioamnionitis (G), meconium aspiration syndrome (H), respiratory distress syndrome (I), shoulder dystocia (J), and brachial plexus injury^‖ (K). *Mode of delivery was a three category outcome modeled using multinomial logistic regression. ^†Includes postpartum hemorrhage, third-or-fourth degree perineal lacerations, unplanned surgical procedure, uterine rupture, maternal intensive care unit admission, sepsis, and endometritis. ^‡Models for infant death did not converge at 41 weeks of gestation. ^§Number of observations with missing values on NICU admission, by parity (nulliparous; parous): 39 weeks of gestation (21; 5), 40 weeks of gestation (1; 30), 41 weeks of gestation (12; 5). ^‖Models for brachial plexus injury did not converge among nulliparous patients at 41 weeks of gestation.

Figure 2

Adjusted odds ratios for elective labor induction, as compared to expectant management, and pregnancy outcomes among obese women. A–K display adjusted odds ratios, stratified by parity, for elective induction of labor (compared with expectant management) and pregnancy outcomes among obese women and their offspring. Models were adjusted for maternal age, education, and race and ethnicity; first-trimester prenatal care initiation; payment source for delivery; birth year; obesity class; and delivery at a teaching hospital. Cesarean delivery (A), operative vaginal delivery* (B), severe maternal morbidity^† (C), infant death^‡ (D), neonatal intensive care unit (NICU) admission^§ (E), macrosomia (≥4,500 g) (F), chorioamnionitis (G), meconium aspiration syndrome (H), respiratory distress syndrome (I), shoulder dystocia (J), and brachial plexus injury^‖ (K). *Mode of delivery was a three category outcome modeled using multinomial logistic regression. ^†Includes postpartum hemorrhage, third-or-fourth degree perineal lacerations, unplanned surgical procedure, uterine rupture, maternal intensive care unit admission, sepsis, and endometritis. ^‡Models for infant death did not converge at 41 weeks of gestation. ^§Number of observations with missing values on NICU admission, by parity (nulliparous; parous): 39 weeks of gestation (21; 5), 40 weeks of gestation (1; 30), 41 weeks of gestation (12; 5). ^‖Models for brachial plexus injury did not converge among nulliparous patients at 41 weeks of gestation.