General Obstetrics and Gynecology ObstetricsPlacenta previa in singleton and twin births in the United States, 1989 through 1998: A comparison of risk factor profiles and associated conditions☆
Section snippets
Cohort composition
Data for this large, population-based retrospective cohort study were derived from the US natality data files from 1989 to 1998. These data are assembled by the National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention, under a cooperative agreement with all the 50 states and the District of Columbia. These natality data files, produced annually, include statistical data from birth that are provided to the NCHS by the individual states, under the Vital
Results
Placenta previa was recorded in 2.8 (n = 104,754) and 3.9 (n = 3,793) per 1,000 singleton and twin live births, respectively (Table I).
Maternal characteristic Singleton births Twin births Number of births Placenta previa* Rate Unadjusted RR 95% CI Number of births Placenta previa* Rate Unadjusted RR 95% CI Total 37,956,020 2.8 — 961,578 3.9 — Maternal age
Comment
Despite small differences in the magnitude and strength of the association of risk factors for placenta previa between the singleton and twin cohorts, risk factor profiles appear fairly similar. Nonetheless, placenta previa occurs 40% more frequently among twin pregnancies than singleton pregnancies without any obvious patterns. Obvious strengths of this study include the large, population-based nature of the data, perhaps the largest series on placenta previa ever reported to date. In
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