Medical Abortion Found as Safe as Surgical Termination

BETHESDA, Md., Aug. 15 -- Medical abortion does not lead to extra adverse effects on outcomes of a first subsequent pregnancy, compared with surgical abortion, found a nationwide Danish registry.

The registry revealed essentially no differences between the outcomes of subsequent pregnancies of 2,710 women who had first-trimester medical abortions and 9,104 who had surgical abortions.

There were similar rates of ectopic pregnancy, spontaneous abortion, preterm birth, and births with low birth weight, Jun Zhang, Ph.D., M.D., of the National Institute of Child Health and Human Development, and colleagues, reported in the Aug. 16 issue of The New England Journal of Medicine.

Dr. Zhang and colleagues reviewed outcome data on the 11,814 early-pregnancy terminations included in the Danish National Induced Abortion Registry. The registry has maintained computerized records of all induced abortions performed in Denmark since 1973.

Surgical and medical procedures were coded separately. The researchers also recorded the type and dosage of drugs used to perform medical abortions -- mifepristone, misoprostol, or a combination of the two, or other prostaglandin analogs.

"Our nationwide cohort study provides evidence that medical abortion is at least as safe as surgical abortion with respect to the risks of ectopic pregnancy, spontaneous abortion, low birthweight, and preterm birth in the first subsequent pregnancy," the authors concluded.

The effect of medical abortion on subsequent pregnancy outcomes had remained unclear despite the fact that more than 360,000 women in the United States had the medical procedure from 2000 (when the FDA approved mifepristone for the indication) to 2004. Use of the medical alternative to surgical abortion continues to increase, the authors stated.

Of 30,349 women included in the Danish abortion registry, 16,883 had a total of 17,170 pregnancies after the abortion. After exclusion of pregnancies for various reasons (primarily because abortion occurred after nine weeks' gestation), 11,814 pregnancies involving 11,682 women formed the basis for the analysis.

Outcomes of subsequent pregnancies consisted of 10,018 live births, 1,468 spontaneous abortions, 36 stillbirths, and 274 ectopic pregnancies. Comparing outcomes of pregnancies after medical abortions versus those after surgical abortions, the investigators found no difference in the adjusted relative risk for:

• Ectopic pregnancy, 2.4% versus 2.3% (RR 1.04, CI 0.76-1.41)
• Spontaneous abortion, 12.2% versus 12.7% (RR 0.87, CI 0.72-1.05)
• Preterm birth, 5.4% versus 6.7% (RR 0.88, CI 0.66-1.18)
• Low birth weight, 4.0% versus 5.1% (RR 0.82. CI 0.61-1.11)

The small number of stillbirths precluded any meaningful statistical analysis, the authors stated. Gestational age at medical abortion had no significant correlations with any of the adverse outcomes.

Rates of adverse outcomes in the study were consistent with those reported in previous studies, Dr. Zhang and colleagues noted. Additionally, the rate of failed medical abortion followed by a surgical procedure (6.9%) also was consistent with rates in previous clinical studies.

"Because our study drew from the entire population of Denmark during the study period and because follow-up was almost complete, the study was not susceptible to selection bias," the authors wrote. "The large sample also provided sufficient power to detect a small effect, if one truly existed."