Complications in first pregnancy linked to preterm birth in second pregnancy

Women who experience complications during their first pregnancy may have an increased risk for preterm birth during their second pregnancy, according to research published in BMJ.

“Clinical guidelines for identifying pregnancies at risk of preterm birth do not mention previous complications in a term first pregnancy as a risk factor,” Liv G. Kvalvik, MD, PhD, associate professor and postdoctoral fellow at the University of Bergen in Bergen, Norway, and colleagues wrote.

Kvalvik and colleagues used population-based data from the Medical Birth Registry of Norway from 1999 to 2015. The registry contains data on births past 16 weeks gestation and includes participants’ demographic information, medical history, pre- and postnatal information, smoking status and gestational age.

Researchers evaluated the occurrence of adverse birth outcomes in full-term pregnancies, including preeclampsia, placental abruption, stillbirth, neonatal death and infants who were small for their gestational age.

 

Women who experience complications during their first pregnancy may have an increased risk for preterm birth during their second pregnancy, according to research published in BMJ.

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A total of 302,192 women who gave birth to a second child during the study period were included in the study.

Kvalvik and colleagues found the risk for preterm birth was 5.9% during the first pregnancy among all women included in the study. In women who had a full-term birth during the first pregnancy, 4.2% experienced preeclampsia, 2.4% had infants who were small for their gestational age, 0.2% experienced placental abruption and 0.2% experienced a stillbirth.

Among women who had a preterm birth during their first pregnancy, the risk for preterm birth during their second pregnancy was 18.1%, according to the researchers. They determined the relative risk was 5.5 (95% CI, 5.3-5.7).

Among women who had a full-term birth during their first pregnancy, Kvalvik and colleagues found the absolute risk of preterm birth during the second pregnancy was 3.1% in those who did not have complications. For those with complications during their first pregnancy, the absolute risk was 6.1% after preeclampsia, 7.3% after placental abruption, 13.1% after stillbirth and 10% after a neonatal death.

Compared with having a first pregnancy and birth without complications, the risk for preterm birth doubled with any one complication during the first pregnancy (RR = 2, 95% CI, 1.9-2.1; absolute risk = 6.2%), and more than tripled with two or more complications (RR = 3.5; 95% CI, 2.9-4.2; absolute risk = 10.9%).

“These findings might inform antenatal clinical care by helping to identify women at increased risk of preterm delivery,” Kvalvik and colleagues wrote. “Further exploration of the causal factors underlying these shared risks might provide insight into fundamental biological mechanisms that link a broad range of pregnancy complications.” – by Erin Michael

Disclosures: Kvalvik reports receiving grants from the US-Norway Fulbright Foundation for Educational Exchange during the conduct of the study. Please see study for all other authors’ relevant financial disclosures.