Methods
From 2008-2011, we assembled a cohort of women and their neonates who were born in any of the 25 hospitals in the Maternal-Fetal Medicine Units Network. This APEX study was designed to develop quality measures for intrapartum obstetric care. The APEX study was approved by the institutional review board at each participating institution under a waiver of informed consent. This article is a planned secondary analysis of the data that were collected during APEX.
A full description of the methods of data collection has been described previously. In short, any patient who delivered at a hospital, was at least 23 weeks of gestation, and had a live fetus on admission was included. Data were collected on randomly selected days, chosen by computer-generated random selection, that occurred over a 3-year period (March 2008 to February 2011). The medical records for all eligible women and babies were abstracted by trained and certified research personnel and entered into a web-based data entry system. Data that were recorded included demographic characteristics, details of the medical and obstetric history, information about intrapartum and postpartum events, and maternal and neonatal outcomes. Maternal data were collected until discharge, and neonatal data were collected up until discharge or until 120 days of age, whichever came first.
The present analysis includes nulliparous women with singleton, vertex, nonanomalous gestations who delivered from 38 0/7 to 41 6/7 weeks. We excluded women who delivered at >41 6/7 weeks of gestation because postdated pregnancies, by definition, is an indication for induction. Additionally, women in our analysis did not have a scheduled nonmedically indicated cesarean delivery. Additionally, they did not have any of the following problems: pregestational or gestational diabetes mellitus, placenta accreta, placenta previa, placental abruption, use of anticoagulation, previous myomectomy, cocaine/methamphetamine use, chronic hypertension, or preeclampsia diagnosed at <38 weeks of gestation. This was done to ensure that we had a low-risk cohort that was eligible for a nonmedically indicated induction as opposed to an indicated induction. Women were classified as having had a nonmedically indicated induction if they were coded as having had an elective induction or if an induction was performed without any other medical indication apparent in the chart. The study group assignment to nonmedically indicated vs expectantly treated was assigned after the entire data set was collected.
Maternal outcomes that were chosen a priori were postpartum hemorrhage, third- and fourth-degree lacerations, peripartum infection, mode of delivery, time from admission to delivery, and delivery to discharge. Neonatal outcomes chosen a priori were neonatal intensive care unit (NICU) admission, hyperbilirubinemia that required treatment, an adverse respiratory outcome composite (respiratory distress syndrome, continuous positive airway pressure, or ventilator support started within 24 hours of birth on ≥1 days delivery), and an adverse neonatal outcome composite (5-minute Apgar score <4, skeletal fracture other than of the clavicle, facial nerve palsy, brachial plexus palsy, subgaleal hemorrhage, ventilator support within 24 hours on ≥2 days, hypoxic ischemic encephalopathy, stillbirth after hospital admission, or neonatal death).
Maternal and neonatal outcomes for women who underwent nonmedically indicated induction within each week of gestation were compared with those of women who reached that week and were treated expectantly (ie, they did not undergo a nonmedically indicated induction). For example, women who underwent a nonmedically indicated induction at 38 weeks of gestation were compared with those who did not undergo a nonmedically indicated induction at 38 weeks of gestation and thus were expectantly treated from gestational week 38. Women in the expectantly treated group could go on to go into labor or to have an indication for delivery. Women who had an indication for induction and were delivered while in the expectant treatment group remained in the expectant treatment group. Multivariable regression was used to adjust for hospital, maternal age, race/ethnicity, body mass index, cigarette use, and insurance status. Odds ratios, adjusted means, and 95% confidence intervals are presented. All tests were 2-tailed, and a probability value of < .05 was used to define statistical significance. No imputation for missing data was performed. Analyses were performed with SAS software (SAS Institute Inc, Cary, NC).
Results
Data were collected from 115,502 women, of whom 31,169 women met our inclusion criteria. Most of the eligible women were in their twenties, were non-Hispanic white, and were nonsmokers. Most women had a body mass index of >25 kg/m 2 . Women who underwent nonmedically indicated induction were more likely to have private insurance, be of older maternal age, and be obese ( Table 1 ).
| Demographic | Weeks of gestation, n (%) | |||||
|---|---|---|---|---|---|---|
| 38 | 39 | 40 | ||||
| Nonmedically indicated induction (n = 210) | Expectant management (n = 28,468) | Nonmedically indicated induction (n = 815) | Expectant management (n = 23,212) | Nonmedically indicated induction (n = 1676) | Expectant management (n = 14,086) | |
| Maternal age, y | ||||||
| <20 | 25 (11.9) | 5547 (19.5) | 108 (13.3) | 4421 (19.1) | 208 (12.4) | 2618 (18.6) |
| 20-24.9 | 67 (31.9) | 7607 (26.7) | 262 (32.2) | 6164 (26.6) | 403 (24.1) | 3674 (26.1) |
| 25-29.9 | 72 (34.3) | 7144 (25.1) | 254 (31.2) | 5850 (25.2) | 499 (29.8) | 3500 (24.9) |
| 30-34.9 | 29 (13.8) | 5914 (20.8) | 132 (16.2) | 4901 (21.1) | 387 (23.1) | 3079 (21.9) |
| ≥35 | 17 (8.1) | 2256 (7.9) | 59 (7.2) | 1876 (8.1) | 179 (10.7) | 1215 (8.6) |
| Race/ethnicity | ||||||
| Non-Hispanic white | 77 (36.7) | 13,518 (47.5) | 516 (63.3) | 11,203 (48.3) | 1018 (60.7) | 7081 (50.3) |
| Non-Hispanic black | 80 (38.1) | 5785 (20.3) | 133 (16.3) | 4669 (20.1) | 269 (16.1) | 2782 (19.8) |
| Non-Hispanic Asian | 9 (4.3) | 1895 (6.7) | 53 (6.5) | 1505 (6.5) | 100 (6.0) | 798 (5.7) |
| Hispanic | 35 (16.7) | 5461 (19.2) | 80 (9.8) | 4363 (18.8) | 219 (13.1) | 2565 (18.2) |
| Other | 9 (4.3) | 1809 (6.4) | 33 (4.1) | 1472 (6.3) | 70 (4.2) | 860 (6.1) |
| Body mass index, kg/m 2 | ||||||
| <25 | 38 (18.1) | 3962 (14.1) | 128 (15.8) | 3022 (13.2) | 167 (10.0) | 1620 (11.7) |
| 25-29.9 | 65 (31.0) | 11,552 (41.2) | 302 (37.3) | 9512 (41.6) | 632 (37.9) | 5692 (41.0) |
| 30-34.9 | 57 (27.1) | 7680 (27.4) | 231 (28.5) | 6294 (27.5) | 507 (30.4) | 3966 (28.6) |
| 35-39.9 | 30 (14.3) | 3080 (11.0) | 102 (12.6) | 2545 (11.1) | 202 (12.1) | 1635 (11.8) |
| ≥40 | 20 (9.5) | 1772 (6.3) | 47 (5.8) | 1501 (6.6) | 159 (9.5) | 979 (7.1) |
| Smoking | 14 (6.7) | 2178 (7.7) | 53 (6.5) | 1803 (7.8) | 143 (8.5) | 1116 (7.9) |
| Private insurance | 112 (53.3) | 15,540 (55.1) | 580 (71.3) | 12,724 (55.3) | 1160 (69.5) | 7726 (55.4) |
Neonatal complications were either less frequent or not different in association with nonmedically indicated induction ( Tables 2-4 ). In particular, NICU admission (odds ratio [OR], 0.66; 95% confidence interval [CI], 0.47–0.93) and the respiratory composite (OR, 0.62; 95% CI, 0.41–0.94) were lower among women who underwent nonmedically indicated induction at 39 and at 40 weeks of gestation, respectively.
| Variable | Nonmedically indicated induction, n (%) | Expectant management, n (%) | Odds ratio a | 95% CI |
|---|---|---|---|---|
| Neonatal outcomes | ||||
| Neonatal intensive care unit admission | 12 (5.7) | 2201 (7.7) | 1.17 | 0.63–2.20 |
| Respiratory composite | 3 (1.4) | 574 (2.0) | 1.62 | 0.48–5.49 |
| Hyperbilirubinemia requiring treatment | 9 (4.3) | 1288 (4.5) | 1.09 | 0.53–2.24 |
| Neonatal composite | 0 | 220 (0.8) | — | — |
| Maternal outcomes | ||||
| Postpartum hemorrhage | 0 | 519 (1.9) | — | — |
| Third- and fourth-degree lacerations | 8 (3.8) | 1710 (6.0) | 0.54 | 0.26–1.13 |
| Peripartum infection | 5 (2.4) | 3009 (10.6) | 0.39 | 0.16–0.98 |
| Mode of delivery | ||||
| Spontaneous vaginal | 124 (59.1) | 19246 (67.6) | ||
| Operative vaginal | 15 (7.1) | 2797 (9.8) | 0.88 | 0.50–1.55 |
| Cesarean section | 71 (33.8) | 6425 (22.6) | 1.50 | 1.08–2.08 |
| Median (interquartile range) | Adjusted mean a (95% CI) | Median (interquartile range) | Adjusted mean a (95% CI) | |
|---|---|---|---|---|
| Time from labor and delivery admission to delivery, hr | 16 (14–20) | 17.85 (16.67–19.03) b | 11 (7–16) | 13.93 (13.70–14.16) |
| Time from delivery to discharge, d | 2 (2–3) | 2.81 (2.51–3.11) | 2 (2–3) | 2.70 (2.64—2.75) |
a Adjusted for maternal age, race/ethnicity, body mass index, cigarette use, insurance status, and hospital stay
| Variable | Nonmedically indicated induction, n (%) | Expectant management, n (%) | Odds ratio a | 95% CI |
|---|---|---|---|---|
| Neonatal outcomes | ||||
| Neonatal intensive care unit admission | 41 (5.0) | 1809 (7.8) | 0.66 | 0.47–0.93 |
| Respiratory composite | 14 (1.7) | 482 (2.1) | 0.69 | 0.39–1.20 |
| Hyperbilirubinemia requiring treatment | 47 (5.8) | 1004 (4.3) | 1.01 | 0.73–1.40 |
| Neonatal composite | 7 (0.9) | 178 (0.8) | 1.51 | 0.68–3.35 |
| Maternal outcomes | ||||
| Postpartum hemorrhage | 9 (1.2) | 442 (2.0) | 0.79 | 0.39–1.58 |
| Third- and fourth-degree lacerations | 35 (4.3) | 1451 (6.3) | 0.60 | 0.42–0.86 |
| Peripartum infection | 47 (5.8) | 2576 (11.1) | 0.66 | 0.49–0.90 |
| Mode of delivery | ||||
| Spontaneous vaginal | 511 (62.7) | 15366 (66.2) | ||
| Operative vaginal | 94 (11.5) | 2314 (10.0) | 1.10 | 0.87–1.40 |
| Cesarean section | 210 (25.8) | 5532 (23.8) | 1.13 | 0.94–1.36 |
| Median (interquartile range) | Adjusted mean a (95% CI) | Median (interquartile range) | Adjusted mean a (95% CI) | |
|---|---|---|---|---|
| Time from labor and delivery admission to delivery, hr | 14 (10–19) | 17.28 (16.66–17.91) b | 11 (7–17) | 14.20 (13.95–14.45) |
| Time from delivery to discharge, d | 2 (2–3) | 2.78 (2.62–2.94) | 2 (2–3) | 2.71 (2.64–2.77) |
a Adjusted for maternal age, race/ethnicity, body mass index, cigarette use, insurance status, and hospital stay
| Variable | Nonmedically indicated induction, n (%) | Expectant management, n (%) | Odds ratio a | 95% CI |
|---|---|---|---|---|
| Neonatal outcomes | ||||
| Neonatal intensive care unit admission | 126 (7.5) | 1172 (8.3) | 0.87 | 0.71–1.06 |
| Respiratory composite | 26 (1.6) | 321 (2.3) | 0.62 | 0.41–0.94 |
| Hyperbilirubinemia requiring treatment | 95 (5.7) | 578 (4.1) | 1.02 | 0.80–1.30 |
| Neonatal composite | 8 (0.5) | 125 (0.9) | 0.55 | 0.26–1.15 |
| Maternal outcomes | ||||
| Postpartum hemorrhage | 35 (2.2) | 297 (2.2) | 1.09 | 0.75–1.60 |
| Third- and fourth-degree lacerations | 99 (5.9) | 938 (6.7) | 0.82 | 0.66–1.03 |
| Peripartum infection | 143 (8.5) | 1724 (12.2) | 0.87 | 0.72–1.05 |
| Mode of delivery | ||||
| Spontaneous vaginal | 930 (55.5) | 8861 (62.9) | ||
| Operative vaginal | 176 (10.5) | 1453 (10.3) | 1.05 | 0.88–1.26 |
| Cesarean section | 570 (34.0) | 3772 (26.8) | 1.30 | 1.15–1.46 |
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