Medline ® Abstracts for References 5,6

BACKGROUND: Although rare, placental abruption is implicated in disproportionately high rates of perinatal morbidity and mortality. Understanding geographic and temporal variations may provide insights into possible amenable factors of abruption. We examined abruption frequencies by maternal age, delivery year, and maternal birth cohorts over three decades across seven countries.

METHODS: Women that delivered in the US (n = 863,879; 1979-10), Canada (4 provinces, n = 5,407,463; 1982-11), Sweden (n = 3,266,742; 1978-10), Denmark (n = 1,773,895; 1978-08), Norway (n = 1,780,271, 1978-09), Finland (n = 1,411,867; 1987-10), and Spain (n = 6,151,508; 1999-12) were analyzed. Abruption diagnosis was based on ICD coding. Rates were modeled using Poisson regression within the framework of an age-period-cohort analysis, and multi-level models to examine the contribution of smoking in four countries.

RESULTS: Abruption rates varied across the seven countries (3-10 per 1000), Maternal age showed a consistent J-shaped pattern with increased rates at the extremes of the age distribution. In comparison to births in 2000, births after 2000 in European countries had lower abruption rates; in the US there was an increase in rate up to 2000 and a plateau thereafter. No birth cohort effects were evident. Changes in smoking prevalence partially explained the period effect in the US (P = 0.01) and Sweden (P<0.01).

CONCLUSIONS: There is a strong maternal age effect on abruption. While the abruption rate has plateaued since 2000 in the US, all other countries show declining rates. These findings suggest considerable variation in abruption frequencies across countries; differences in the distribution of risk factors, especially smoking, may help guide policy to reduce abruption rates.

OBJECTIVE: Women who have experienced a placental abruption have a risk of recurrence, but exact information to quantify this risk is currently not available. We studied the incidence and recurrence rate of placental abruption in a subsequent pregnancy and the influence of hypertensive disorders.

STUDY DESIGN: We conducted a retrospective national cohort study of all singleton pregnancies that ended from 1999-2007 in the Netherlands. A longitudinal linked national cohort of these women with information on a subsequent singleton delivery was used. We calculated and compared incidence and recurrence rates of placental abruption for women in total, stratified by gestational age of first placental abruption and by the presence of a hypertensive disorder in their first pregnancy.

RESULTS: We studied 1,570,635 women of which 3496 (0.22%) experienced a placental abruption. Information was available on a subsequent singleton delivery for 264,424 deliveries. Of these, 521 women (0.20%) had a placental abruption in the first pregnancy vs 214 women(0.08%) in the second pregnancy. The risk of placental abruption in a subsequent pregnancy was significantly higher in women with a previous placental abruption compared with women without (5.8% vs 0.06%; adjusted odds ratio [aOR], 93; 95% confidence interval [CI], 62-139). Women with a placental abruption that occurred at term in their first pregnancy were more at risk for recurrence (aOR, 188; 95% CI, 116-306) than women with a preterm (aOR, 52; 95% CI, 25-111) or early preterm (<32 weeks of gestation) placental abruption in their first pregnancy (aOR, 39; 95% CI, 13-116). Placental abruption was more frequent among women with a hypertensive disorder compared with normotensive women (0.44% vs 0.16%; odds ratio, 2.7; 95% CI, 2.3-3.3). Women with a hypertensive disorder were less at risk for recurrence than were normotensive women (aOR, 0.68; 95% CI, 0.27-1.6). No interaction between a hypertensive disorder in the first pregnancy and the recurrence risk was found.

CONCLUSION: Women with a placental abruption in their first pregnancy have a greatly increased risk of placental abruption in a subsequent pregnancy. Hypertensive disorders increase the risk of placental abruption but do not increase the recurrence rate in a subsequent pregnancy. We suggest elective induction from 37 weeks of gestation for women with a history of placental abruption at term in a previous pregnancy.