Women who have experienced stillbirth in a previous pregnancy may be up to four times higher risk of stillbirth in a subsequent pregnancy, according to researchers.
Stillbirth - the death of a fetus after 20 weeks gestation - occurs in approximately 1 in 160 pregnancies in the US, with the majority happening before labor.
Poor fetal growth, placental problems - such as placental abruption - birth defects, infections and chronic health conditions among mothers are some of the known causes of stillbirth.
But as study author Sohinee Bhattacharya and colleagues from the UK's University of Aberdeen note, the cause of stillbirth is often unclear, and it is important to gain a better understanding of factors that may contribute to increased risk of stillbirth.
"Stillbirth is one of the most common adverse obstetric outcomes and a traumatic experience for parents yet until recently was largely ignored," they note. "Couples who have experienced a stillbirth need to understand why it happened and want to know the risk for future pregnancies."
For their study, Bhattacharya and colleagues set out to see how a history of stillbirth may impact the risk of experiencing stillbirth in subsequent pregnancies.
The team analyzed data from 13 cohort and three case-controlled studies involving 3,412,079 women from the US, Australia, Scotland, Denmark, Israel, Norway, Sweden, the Netherlands, among other high-income countries.
Of these women, 99.3% (3,387,538) had a live birth in an initial pregnancy, while 0.7% (24,541) of the women had a stillbirth in an initial pregnancy - defined in the study as the death of a fetus after 20 weeks of pregnancy or a weight of at least 400 g at birth.
Pregnancies after a stillbirth 'should be closely monitored for fetal compromise'
The researchers identified 14,283 stillbirths in a subsequent pregnancy. Of these, 606 (2.5%) occurred among women who experienced stillbirth in a previous pregnancy, while 0.4% occurred among women who had no history of stillbirth.
After adjusting for potential confounders, such as maternal age, smoking status during pregnancy and socioeconomic status, the team calculated that women who experienced a stillbirth in a previous pregnancy had up to four times greater risk of experiencing stillbirth in a subsequent pregnancy, compared with women who had no history of stillbirth.
The authors note that only two studies included in their analysis included women who had a history of unexplained stillbirth, and as such, the subsequent risk of stillbirth among these women was unclear.
Still, the team says their findings support previous research suggesting a history of stillbirth as an important risk factor for stillbirth recurrence, which may have important implications for clinical practice. They add:
"Current management of pregnancies should take account of pregnancy history and make use of pre-pregnancy counseling services.
Based on the available evidence identified by this review, a stillbirth in an initial pregnancy was associated with an increased risk of a subsequent stillbirth, and pregnancies after a stillbirth should be closely monitored with a view to intervene at the first sign of fetal compromise."
In July 2014, Medical News Today reported on a study associating Cesarean section in a first birth with greater risk of subsequent stillbirth and ectopic pregnancy.