IntroductonSince 1986, approximately 1.6 million induced abortions have been performed in the United States each year. 1 As the vast majority of women who undergo abortion eventually wish to deliver, it is important to identify possible deleterious effects of induced abortion on future pregnancy outcome. Many studies report that a single induced abortion does not increase a woman's risk for delivering a lowbirth-weight infant in a subsequent pregnancy.2-6 However, the effect of multiple induced abortions is less clear.7 Multiple induced abortions may increase the likelihood of pregnancy loss or of preterm delivery resulting in a low-birth-weight infant in two general ways: cervical trauma from forced mechanical or rapid dilatation during the abortion procedure, or cervical and uterine adhesions due to curettage or infection.Most studies of the risks of induced abortion on future reproductive outcome were conducted before a large proportion of women had the opportunity to have two, three, or more induced abortions.We report results from a population-based study of risk of low birth weight in women with multiple induced abortions prior to their first birth.
MethodsThe Washington State birth certificate uses a check-box format to record information on demographic characteristics, complications of labor and delivery, and birth outcome. Information on history of prior induced abortions-specifically, the number ofprior induced abortions and the date ofthe last induced or spontaneous abortion-was added to the birth certificate in 1984.Women without a prior live birth who resided in one of the three most urban counties of Washington State (King, Pierce, and Spokane) and who delivered a live-born singleton infant between January 1, 1984, and December 31, 1987, were eligible for study. Because only a small proportion of Washington residents are non-White, this analysis was restricted to White women. Two thousand women without a history of induced abortion and 2000 women with one prior abortion were randomly sampled from the population using the birth certificate tapes. All eligible women with two (n = 1852), three (n = 522), and four or more (n = 173) induced abortions prior to their birth were identified. Six women were excluded for delivering infants with birth weights considered out of range (less than 450 g [n = 4], greater than 7000 g [n = 2]). The total study population consisted of 6541 White women.Unconditional logistic regression8 was used to provide parameter estimates of the risk of low birth weight (less than 2500 g) associated with one, two, three, and four or more prior induced abortions