Association of discordance in birth weights of dichorionic twins with the incidence of preeclampsia in pregnant women.

OBJECTIVES: Preeclampsia (PE) is more common in multiple pregnancies, especially dichorionic twins, which often show birthweight discordance. The threshold of birthweight discordance linked to increased risk remains unclear, based largely on the Delphi consensus method. This study examines whether discordance independently predicts PE and identifies the most predictive threshold to guide prenatal care.

METHODS: We conducted a retrospective population-based cohort study of 2,546 women with dichorionic twins who delivered in Slovenia between 2013 and 2022, using data from the National Perinatal Information System. The association between twin birthweight discordance, the main independent variable, and PE, the main outcome variable, was determined using multivariate logistic regression. We calculated the crude odds ratio (OR) and adjusted odds ratio (aOR) with a 95 % confidence interval. ROC analysis determined the area under the curve (AUC), the sensitivity, and the false positive rate for predicting PE. Two-sided p-values <0.05 were considered statistically significant.

RESULTS: In our cohort PE occurred in 5.38 %. Compared with a birthweight discordance of <10 %, a discordance >25 % was identified as a statistically significant independent risk factor for PE development (aOR=1.66; 95 % CI 1.10-2.52; p=0.016). Birthweight discordance between 10 and 25 % was not significantly associated with PE. The AUC for predicting PE with birthweight discordance was significant at 55.2 % (51.6-58.8 %). However, at a birthweight discordance threshold of >25 %, only 10.2 % of pregnant women with PE could be identified with 5.8 % false-positive results.

CONCLUSIONS: This study revealed that a birthweight discordance >25 % in dichorionic twins significantly increases PE risk.