“Until recently, a first birth at full term was considered a reduced risk for a preterm delivery in the next pregnancy,” said researcher Jennifer Dunne. “However, there is emerging evidence that a complicated first pregnancy, regardless of whether the baby was delivered early or at full-term, increases the subsequent risk of a baby being born prematurely.”
Preeclampsia increases risk of preterm birth
For the study, the researchers analyzed data from more than 125,000 women who had multiple births in Australia between 1998 and 2015. They paid close attention to four major pregnancy complications that could increase the risk of preterm birth: preeclampsia, stillbirth, low birth weight, and placental abruption.
The study showed that preeclampsia played the biggest role in increasing the risk for preterm birth. For women who delivered preterm as a result of preeclampsia, there was a higher risk for delivering early a second time if preeclampsia returned.
“When both pregnancies were complicated by preeclampsia, the risk of a subsequent preterm birth increased 10-fold after an initial term birth and 17-fold when the first birth was preterm, compared to women who had an uncomplicated first pregnancy,” Dunne said. “This study also found that there was a three-fold higher risk of women experiencing a subsequent case of pre-eclampsia after a preterm birth in the first pregnancy that was not complicated by preeclampsia.”
Preeclampsia not the only pregnancy risk
While preeclampsia was linked with the strongest risk of preterm birth, the researchers also learned that any of the four major pregnancy complications may contribute to early deliveries.
“Having any of the four complications in their first pregnancy puts women at an increased risk of a preterm birth in their next pregnancy, regardless of whether that first birth ended at full term or preterm,” said Dunne. “Likewise, women whose first pregnancy ended in preterm delivery were at an increased risk for each pregnancy complication in the second pregnancy.”
Moving forward, the researchers hope more work is done in this area to better understand women’s health risks during pregnancy and delivery.
“The findings of this study will help clinicians to better identify women who are at an increased risk of either a preterm birth or complications in their subsequent pregnancies,” Dunne said. “Further research is now needed to reveal the specific pathways that explain these strong links between pregnancy complications and preterm births, whether they be genetic, pathological, and behavioral or recurrent issues.”