Associations between hypertensive diseases of pregnancy and birthweight outcomes in twin pregnancies: A large‐scale retrospective cohort study

OBJECTIVE: This study aimed to assess the association between hypertensive disorders of pregnancy (HDPs) and birthweight outcomes in twin pregnancies, an area that remains underexplored compared to the well-documented short- and long-term effects of HDPs in singleton pregnancies. METHODS: In this retrospective cohort study (2017-2025) of 4530 twin pregnancies, multinomial logit regression was used to evaluate associations of HDPs and their subtypes with small for gestational age (SGA) and birthweight discordance (≥20%). Interaction analyses by chorionicity and dichorionic (DC)-restricted sensitivity analyses were performed. RESULTS: Among 4530 twin pregnancies, 190 (4.2%) had gestational hypertension (GH) and 443 (9.8%) had preeclampsia (PE). After accounting for confounding factors and adjusting for multiple comparisons, PE was significantly associated with an increased risk of discordant twins with at least one SGA neonate (adjusted relative risk ratio [aRRR]: 2.05; 95% CI: 1.48-2.84), whereas GH showed no significant association. Specifically, early-onset PE (aRRR: 3.67; 95% CI: 2.23-6.01) and PE without severe features (aRRR: 2.00; 95% CI: 1.42-2.83) were independently associated with this elevated risk. Interaction analyses revealed that chorionicity did not significantly modify these risk effects. In sensitivity analyses restricted to DC twins, the positive association between PE and discordant twins with SGA remained robust, whereas the association with concordant twins with SGA did not retain statistical significance. CONCLUSION: Preeclampsia, rather than GH, is a significant independent risk factor for adverse fetal growth outcomes in twin pregnancies and is particularly associated with birthweight discordance complicated by SGA. These associations are fundamentally consistent across chorionicity types.