Elsevier

Obstetrics & Gynecology

Volume 102, Issue 2, August 2003, Pages 287-293
Obstetrics & Gynecology

Impact of labor induction, gestational age, and maternal age on cesarean delivery rates

https://doi.org/10.1016/S0029-7844(03)00531-3Get rights and content

Abstract

Objective

To quantify the impact of labor induction and maternal age on cesarean delivery rates in nulliparous and multiparous women between 36 and 42 weeks’ gestation.

Methods

We performed a retrospective cohort study on 14,409 women delivering at two teaching hospitals in metropolitan Boston during 1998 and 1999. Women who had contraindications to labor, including a prior cesarean delivery, were excluded. The risks for cesarean delivery by induction status, gestational age by completed week between 36 and 42 weeks, maternal age <35, 35–39, and ≥40 years, and stratified by parity, were calculated by logistic regression.

Results

In nulliparas, labor induction was associated with an increase in cesarean delivery from 13.7% to 24.7% (adjusted odds ratio [OR] 1.70; 95% confidence interval [CI] 1.48, 1.95]). In multiparas, induction was associated with an increase from 2.4% to 4.5% (OR 1.49; 95% CI 1.10, 2.00). Other variables that placed a nulliparous woman at increased risk for cesarean delivery included maternal age of at least 35 years and gestational ages over 40 weeks. For multiparas, only maternal age 40 years or older and gestational age of 41 weeks were associated with an increase in cesarean deliveries.

Conclusion

Induction of labor, older maternal age, and gestational age over 40 weeks each independently increase the risk for cesarean delivery in both nulliparous and multiparous women. Although the relative risk from induction is similar in nulliparas and multiparas, the absolute magnitude of the increase is much greater in nulliparas (11% versus 2.1%).

Section snippets

Materials and methods

Our sample was collected from Beth Israel Deaconess Medical Center and Brigham and Women’s Hospital in Boston, the two largest obstetric services in the city. The delivery services at each of these two institutions are comprised of a variety of practice models, including resident practices, maternal–fetal medicine services, midwifery services caring for community health center patients and health maintenance organization patients, and conventional private practices staffed by one to six

Results

Overall, the primary cesarean delivery rate in the cohort was 10.8%. The difference in cesarean delivery rates between the two hospitals was a function of different rates of assisted vaginal delivery. The proportions of women in both institutions who delivered spontaneously were virtually identical (80.3% versus 80.0%).

Among the 7372 nulliparous women in the sample, 2227 (30%) had induced labor. Induced nulliparas had a 24.7% cesarean delivery rate, compared with a 13.7% cesarean delivery rate

Discussion

Our study demonstrates that labor induction, parity, maternal age, and birth weight extremes played significant roles in determining risk for cesarean delivery in our cohort of ethnically diverse and relatively low-risk obstetric patients. Women with hypertension and diabetes also had an increased risk for cesarean delivery but did not contribute substantially to the overall cesarean delivery rate because of their low prevalence. Induction was associated with a 70% increase in the risk of

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    Citation Excerpt :

    This result is consistent with the lack of harmful effects by induction for FGR in the DIGITAT trial [8]. Maternal age and nulliparity have already been reported in the literature as prognostic factors for caesarean delivery [5,28]. An abnormal umbilical artery Doppler velocimetry is a risk factor characteristic of the FGR population, and several authors have shown that this abnormality is a risk factor for caesareans [29].

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