Placental weight in the first pregnancy and risk for preeclampsia in the second pregnancy: A population-based study of 186 859 women

Objective: To study whether placental weight in the first pregnancy is associated with preeclampsia in the second pregnancy.

Study design: In this population-based study, we included all women with two consecutive singleton pregnancies reported to the Medical Birth Registry of Norway during 1999-2012 (n=186 859). Placental weight in the first pregnancy was calculated as z-scores, and the distribution was divided into five groups of equal size (quintiles). We estimated crude and adjusted odds ratios with 95% confidence intervals for preeclampsia in the second pregnancy according to quintiles of placental weight z-scores in the first pregnancy. The 3rd quintile was used as the reference group.

Results: Among women without preeclampsia in the first pregnancy, 1.4% (2507/177 149) developed preeclampsia in the second pregnancy. In these women, the risk for preeclampsia in the second pregnancy was associated with placental weight in the first pregnancy in both lowest (crude odds ratio (cOR) 1.30, 95% confidence interval (CI); 1.14-1.47) and highest quintile (cOR 1.20, 95% CI; 1.06-1.36). The risk associated with the highest quintile of placental weight was confined to term preeclampsia. Among women with preeclampsia in the first pregnancy, 15.7% (1522/9710) developed recurrent preeclampsia, and the risk for recurrent preeclampsia was associated with placental weight in lowest quintile in the first pregnancy (cOR 1.30, 95% CI; 1.10-1.55). Adjustment for interval between pregnancies, maternal diabetes, age, and smoking in the first pregnancy did not alter these estimates notably.

Conclusion: Placental weight in the first pregnancy might help to identify women who could be at risk for developing preeclampsia in a second pregnancy.