The influence of pregnancy termination on the outcome of subsequent pregnancies: a retrospective cohort study

OBJECTIVE To compare the incidences of preterm delivery, cervical incompetence treated by cerclage, placental implantation or retention problems (ie, placenta praevia, placental abruption and retained placenta) and postpartum haemorrhage between women with and without a history of pregnancy termination. DESIGN  A retrospective cohort study using aggregated data from a national perinatal registry. SETTING All midwifery practices and hospitals in the Netherlands. PARTICIPANTS All pregnant women with a singleton pregnancy without congenital malformations and a gestational age of ≥20 weeks who delivered between January 2000 and December 2007. MAIN OUTCOME MEASURES Preterm delivery, cervical incompetence treated by cerclage, placenta praevia, placental abruption, retained placenta and postpartum haemorrhage. RESULTS A previous pregnancy termination was reported in 16 000 (1.2%) deliveries. The vast majority of these (90-95%) were performed by surgical methods. The incidence of all outcome measures was significantly higher in women with a history of pregnancy termination. Adjusted ORs (95% CI) for cervical incompetence treated by cerclage, preterm delivery, placental implantation or retention problems and postpartum haemorrhage were 4.6 (2.9 to 7.2), 1.11 (1.02 to 1.20), 1.42 (1.29 to 1.55) and 1.16 (1.08 to 1.25), respectively. Associated numbers needed to harm were 1000, 167, 111 and 111, respectively. For any listed adverse outcome, the number needed to harm was 63. CONCLUSIONS In this large nationwide cohort study, we found a positive association between surgical termination of pregnancy and subsequent preterm delivery, cervical incompetence treated by cerclage, placental implantation or retention problems and postpartum haemorrhage in a subsequent pregnancy. Absolute risks for these outcomes, however, remain small. Medicinal termination might be considered first whenever there is a choice between both methods.