Women who experience complications in their first pregnancy but deliver at full term are at increased risk of preterm delivery in their next pregnancy, according to a new Norwegian study.
The researchers behind the study, published in the latest edition of The BMJ, say although women who deliver at term are low risk of having preterm delivery in later pregnancies, it is not understood if pregnancy complications or poor outcomes at birth might increase the risk.
To find out, a research team in Norway and the USA used data from Norway’s Medical Birth Registry linking first and second pregnancies for 302,192 women between 1999 and 2015, looking at term complications of pre-eclampsia, placental abruption, stillbirth, neonatal death, and having a small baby.
They found that women with any of the five complications at term were had a substantially increased risk of preterm delivery in their next pregnancy – with the risk, compared to women with no complications, doubling with one complication and tripling if the woman had two or more.
The observational study established that the absolute risks for preterm delivery in second pregnancy were 3% with none of the five term complications; 6% after term pre-eclampsia; 7% after term placental abruption; 13% after term stillbirth; 10% after term neonatal death; and nearly 7% after term small for gestational age.
Although the researchers say they are unable to establish cause, they say their results are based on high-quality, population-based birth data, and were largely unchanged after a range of further analyses.
They conclude that serious complications in pregnancy at term “imply an increased risk not only of recurrence of the same outcome but also of preterm birth in a subsequent pregnancy. These findings might inform antenatal clinical care by helping to identify women at increased risk of preterm delivery”.
Kvalvik L, Wilcox A, Skjærven R et al. Term complications and subsequent risk of preterm birth: registry based study. BMJ 30 April 2020.
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