Prenatal Care and Birth Outcomes in Twins
Prenatal Care and Birth Outcomes in Twins
Abstract & Commentary
Synopsis: Women with twin gestations are more likely to receive intensive prenatal care and increased medical interventions that may result in more preterm births, while lowering the infant mortality rate for twins.
Source: Kogan MD, et al. JAMA 2000;283:335-341.
To determine the relationship between the intensity of prenatal care and the outcome for twin gestations in the United States between 1981-1997, Kogan and colleagues used data from the National Center for Health Statistics. Intensive prenatal care was defined as a high number of visits, exceeding the recommendation of the American College of Obstetricians and Gynecologists (ACOG) by approximately one SD beyond the mean number of visits for women initiating care within each trimester.
Kogan et al found that there has been a dramatic increase in intensive prenatal care for women with twins from 8.3% in 1981 to 22.7% in 1995. This figure also rose for patients with a single-term birth, from 3.3% to 6.3%. The number of twin births has increased 52% from 1980-1997. Kogan et al found that the preterm birth rate for twins rose from nearly 41% in 1981 to 55% in 1997. Surprisingly, the increased rates of preterm birth were most marked in women who received intensive prenatal care, rising from 35.1% to nearly 56%, a greater increase than that seen for women with twins who received only adequate prenatal care. This increase was noted primarily in births of growth restricted twins between 32-36 weeks gestation after induction of labor or first cesarean delivery. Most importantly, the infant mortality rate in twins for women who received intensive prenatal care declined dramatically from 27.6 per 1000 live births in 1983-1984 to 17.8 per 1000 live births in 1995-1996, a rate that is 50% lower than that observed with adequate prenatal care.
Kogan et al conclude that women with twin gestations are more likely to receive intensive prenatal care and increased medical interventions that may result in more preterm births, while lowering the infant mortality rate for twins.
Comment by Steven G. Gabbe, MD
While multiple births represent only 3% of all deliveries in the United States, in 1997 they accounted for 21% of all low birth weight deliveries, 14% of preterm births, and 13% of infant deaths. Obstetricians are well aware that the rate of multiple gestations has increased, and a visit to any neonatal intensive care unit will demonstrate the contribution to preterm births made by multiple gestations. The increase in multiple gestations, especially high-order multiple births, has been attributed to ovulation induction and other assisted reproductive technologies.
Reports from many perinatal centers have demonstrated that a well-organized program of prenatal care, including more frequent prenatal visits and serial ultrasound studies to evaluate fetal growth and well-being, can reduce adverse outcomes in twin gestations. When intrauterine growth restriction is detected, antepartum fetal surveillance is intensified and corticosteriods may be administered. The perinatal mortality rate may be increased in twins beyond 38 weeks gestation and, so, more twin births may be induced or delivered by cesarean section when that gestational age is reached. The data presented by Kogan et al clearly demonstrate these changes in practice patterns and explain the paradoxical observation that intensive prenatal care for twin gestations has increased in association with a rise in the preterm birth rate for twins. Most importantly, however, the infant mortality rate associated with intensive prenatal care has declined and has remained significantly lower than that for women receiving adequate or less than adequate prenatal care.
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