Birth outcomes after induced abortion: a nationwide register-based study of first births in Finland.

STUDY QUESTION Is the perinatal health of first-born children affected by the mother's previous induced abortion(s) (IAs)? SUMMARY ANSWER Prior IAs, particularly repeat IAs, are correlated with an increased risk of some health problems at first birth; even in a country with good health care quality. WHAT IS KNOWN ALREADY A positive association between IA and risk of preterm birth or a dose-response effect has been found in some previous studies. Limited information and conflicting results on other infant outcomes are available. STUDY DESIGN, SIZE AND DURATION Nationwide register-based study including 300 858 first-time mothers during 1996-2008 in Finland. PARTICIPANTS/MATERIALS, SETTING AND METHODS All the first-time mothers with a singleton birth (obtained from the Medical Birth Register) in the period 1996-2008 (n = 300 858) were linked to the Abortion Register for the period 1983-2008. MAIN RESULTS AND THE ROLE OF CHANCE Of the first-time mothers, 10.3% (n = 31 083) had one, 1.5% had two and 0.3% had three or more IAs. Most IAs were surgical (88%) performed before 12 weeks (91%) and carried out for social reasons (97%). After adjustment, perinatal deaths and very preterm birth (<28 gestational week) suggested worse outcomes after IA. Increased odds for very preterm birth were seen in all the subgroups and exhibited a dose-response relationship: 1.19 [95% confidence interval (CI) 0.98-1.44] after one IA, 1.69 (1.14-2.51) after two and 2.78 (1.48-5.24) after three IAs. Increased odds for preterm birth (<37 weeks) and low birthweight (<2500 g and <1500 g) were seen only among mothers with three or more IAs: 1.35 (1.07-1.71), 1.43 (1.12-1.84) and 2.25 (1.43-3.52), respectively. LIMITATIONS, REASONS FOR CAUTION Observational studies like ours, however large and well-controlled, will not prove causality. WIDER IMPLICATIONS OF THE FINDINGS In terms of public health and practical implications, health education should contain information of the potential health hazards of repeat IAs, including very preterm birth and low birthweight in subsequent pregnancies. Health care professionals should be informed about the potential risks of repeat IAs on infant outcomes in subsequent pregnancy. STUDY FUNDING/COMPETING INTEREST(S) National Institute for Health and Welfare and the Academy of Finland. No competing interests.