The risk of vaginal bleeding within the first 16 weeks of pregnancy is greater for first-time expectant mothers who have had a medication abortion than for those who have never had an abortion, according to a prospective cohort study of nulliparous Chinese women.1 The risk is greatest for women whose medication abortion occurred before seven weeks’ gestation or resulted in curettage or complications. For women who have had a surgical abortion, however, the risk of vaginal bleeding early in a subsequent pregnancy is similar to the risk for women who have had a medication abortion.
Vaginal bleeding is a sign of a high-risk pregnancy and has been associated with past surgical abortion. To explore the association between vaginal bleeding and medication abortion, this study compared rates of vaginal bleeding among pregnant women who had had a medication abortion with those among women who had had a surgical or no abortion.
From 1998 to 2001, investigators recruited women who were 4–16 weeks pregnant from 83 antenatal clinics in Beijing, Chengdu and Shanghai. Eligible women were aged 20–34, had not given birth before and had previously undergone one first-trimester abortion (surgical or medication) or no abortion. Participants completed questionnaires at enrollment, at 28–30 weeks and at delivery, providing information on their reproductive and medical history, including the current pregnancy. Women’s reports of vaginal bleeding were examined overall and for two periods of pregnancy: up to recruitment (the first period) and during follow-up (the second period). Log binomial regression analysis was used to calculate the relative risk of vaginal bleeding while controlling for study center, age, income, residence, season at conception and history of chronic disease.
A total of 14,399 women participated—4,841 of whom had had a medication abortion, 4,705 a surgical abortion and 4,853 no abortion. The mean age at recruitment was 26. Most of the women had at least a high school degree; lived in a city; and were industrial or service workers, or farmers. Levels of tobacco and alcohol use, as well as of chronic disease, were low.
Overall, rates of vaginal bleeding, up to the first follow-up, among women with a history of medication abortion, surgical abortion and no abortion were 17%, 17% and 14%, respectively. After adjustments for potential confounders, the risk of vaginal bleeding was significantly higher for women who had had a medication abortion than for those who had had no abortion (relative risk, 1.2). When medication abortion and vaginal bleeding were examined by period of pregnancy, the increased risk was observed only in the first period (1.3). However, no differences in the risk of vaginal bleeding were found between women who had undergone a medication abortion and those who had had a surgical abortion.
When rates of vaginal bleeding during the first period of pregnancy were compared by gestational age at recruitment, women who had had a medication abortion had a higher rate at every gestational week than women who had had no abortion. However, they had similar rates to women who had had a surgical abortion. No difference in rates was observed among the three groups later in pregnancy.
Finally, the investigators stratified women who had had a medication abortion according to characteristics of the abortion and then compared their risk of vaginal bleeding during the first period of pregnancy with that of women with no abortion history. The risk was similarly elevated for women who had had a medication abortion before age 25 and those who had had one later; the risk also was elevated for women with an interpregnancy interval of less than 12 months and those with longer intervals (relative risk, 1.2–1.3). However, compared with women who had had no abortion, those who had had a medication abortion before seven weeks’ gestation had a significantly greater risk of vaginal bleeding (1.3); women who had had curettage or complications following a medication abortion also experienced a significantly greater risk of vaginal bleeding (1.6 and 2.0, respectively).
The investigators acknowledge the potential underreporting of abortion history among women who had not experienced any pregnancy complications prior to the interview. They also note that the rate of vaginal bleeding, reported by some women at four weeks, might not have fully reflected the rate when recruitment ended at 16 weeks. Finally, given the young age and limited abortion experience of most study participants, the results may not apply to women who have had multiple medication abortions. The investigators conclude that the risk of vaginal bleeding early in pregnancy is more strongly associated with the previous use of mifepristone than with no abortion, especially when the medication abortion took place before seven weeks’ gestation and resulted in curettage or complications.—A. Kott