Risk of hypertensive disorders in pregnancies with non‐immune hydrops fetalis and single fetal effusions

Abstract Introduction Hydrops fetalis carries high risks of morbidity and mortality for the fetus, as well as obstetric risks such as hypertensive disorders, or mirror syndrome, for the pregnant person. We aimed to characterize the prevalence and types of hypertensive disorders diagnosed in pregnancies with non‐immune hydrops fetalis and single effusions, as well as to investigate fetal risk factors for the development of hypertension. Methods This was a secondary analysis of a prospectively enrolled cohort. We included pregnancies with non‐immune hydrops fetalis that demonstrated ≥2 fetal effusions (ascites, pleural effusion, pericardial effusion, and/or skin edema), as well as pregnancies with only one of these effusions. We excluded pregnancies that did not continue beyond 20 weeks gestation as most hypertensive disorders of pregnancy develop after this. Primary outcomes were the prevalence and types of hypertensive disorders diagnosed during pregnancy or within 6 weeks postpartum. Secondary outcomes were the prevalence of hypertensive disorders by number of fetal effusions and presence of an underlying fetal genetic disease. Results Among 116 pregnancies with fetal effusions, 22 (19%) developed hypertensive disorders of pregnancy, with 22% (19/85) and 10% (3/31) of pregnancies with non‐immune hydrops fetalis and single effusions affected, respectively ( p = 0.12). Of those with hypertensive disorders, 8 (36%) developed preeclampsia with severe features, 4 (18%) preeclampsia without severe features, 2 (9%) atypical preeclampsia, and 8 (36%) gestational hypertension; 82% of these diagnoses were made antepartum. The presence of a fetal genetic disease did not result in statistically significant increased risk of hypertensive disorders. Conclusions In this contemporary cohort that continued beyond 20 weeks gestation, 22% with non‐immune hydrops fetalis and 10% with single effusions developed a range of hypertensive disorders of pregnancy, with most arising in the antepartum period. These data allow clinicians to provide more evidence‐based counseling, anticipate obstetric risks, and consider close surveillance strategies for the development of hypertensive disorders in pregnancies with fetal effusions.