Induced abortion and subsequent pregnancy duration.
OBJECTIVE
To examine whether induced abortion influences subsequent pregnancy duration.


METHODS
Women who had their first pregnancies during 1980, 1981, and 1982 were identified in three Danish national registries. A total of 15,727 women whose pregnancies were terminated by first-trimester induced abortions were compared with 46,026 whose pregnancies were not terminated by induced abortions. All subsequent pregnancies until 1994 were identified by register linkage.


RESULTS
Preterm and post-term singleton live births were more frequent in women with one, two, or more previous induced abortions. After adjusting for potential confounders and stratifying by gravidity, the odds ratios of preterm singleton live births in women with one, two, or more previous induced abortions were 1.89 (95% confidence interval [CI] 1.70, 2.11), 2.66 (95% CI 2.09, 3.37), and 2.03 (95% CI 1.29, 3.19), respectively. Odds ratios of post-term singleton live births in women with one, two, or more previous induced abortions were 1.34 (95% CI 1.24, 1.44), 1.50 (95% CI 1.26, 1.78), and 1.58 (95% CI 1.09, 2.28), respectively.


CONCLUSIONS
The study showed an increase in preterm and post-term pregnancies after induced abortions. The risk of post-term delivery was high regardless of the interpregnancy interval, whereas increased risk of preterm delivery was seen mainly when interpregnancy intervals were longer than 12 months.
Zhou
W
W
Danish Epidemiology Science Centre, and the Department of Epidemiology and Social Medicine, Aarhus University, Denmark.
Sørensen
H T
HT
Olsen
J
J
D000028:Abortion, Induced; D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D016015:Logistic Models; D007752:Obstetric Labor, Premature / Q000453:epidemiology; D016017:Odds Ratio; D010298:Parity; D011247:Pregnancy; D018566:Pregnancy, High-Risk; D011273:Pregnancy, Prolonged; D012307:Risk Factors; D013997:Time Factors