Abstract
Background Induction of labor is a common obstetric procedure associated with an increased risk of adverse outcomes. The purpose of this study is to describe maternal characteristics and recent trends in induction of labor based on maternal age and race/ethnicity.
Methods We used the Matched Perinatal Service System (PSS) and Hospital Inpatient records of women delivering in KPSC hospitals between1997–2008 (n=289,576). The PSS database includes all births in KPSC hospitals, ICD-9-CM codes from hospitalization in all KPSC hospitals, and infant birth certificate records. Pregnancies were identified using PSS; maternal and infant characteristics were obtained from the birth certificate, and maternal and infant outcomes were obtained from ICD-9-CM codes. Indication for induction of labor was determined using ICD-9-CM procedure codes (73x) and subjects were grouped into spontaneous labor, clinically indicated, and elective (inductions for which no medical or obstetrical indications was documented) induction groups. We compared event rates in the earliest (1997–1998) versus recent (2007–2008) periods.
Results The elective induction rates increased from 5.4% (2,888 of 53,600) in 1997–1998 to 9.9% (4,384 of 44,094) in 2007–2008 (p<.001). The indicated induction rates increased from 3.4% (1,813 of 53,600) in 1997–1998 to 5.7% (2,523 of 44,094) in 2007–2008 (p<.001). Electively-induced women were more likely to be white, educated, to have initiated prenatal care early in the pregnancy, and smoked during pregnancy compared with those with spontaneous onset of labor. From 1997–1998 to 2007–2008, elective induction rate increased among whites (7.6% [1,177 of 15,506] to 13.2% [1,298 of 9,845], respectively; p<.001), Hispanics (4.9% [1,207 of 24,898] to 9.4% [2,271 of 24,249], respectively; p<.001), and Asian/Pacific-Islanders (3.9% [195 of 4,968] to 6.2% [322 of 5,196], respectively; p<.001). African-Americans had the largest relative increase (4.8% [260 of 5,430] to 10.3% [396 to 3,843], respectively; p<.001). The increases in the rate of elective and indicated inductions were similar according to maternal age categories.
Conclusions Our findings indicate elective induction of labor is rising faster than the rate of indicated induction of labor. The increase in elective induction rate is disconcerting; largely because of the known increased risk this patient population has for adverse perinatal outcome.
