Comparison of body composition change, measured with bioelectrical impedance analysis, between singleton and twin pregnancy: A prospective cohort study.

Objectives: To determine the difference of body composition change measured by bioelectrical impedance analysis (BIA) between singleton and twin pregnancy.

Study Design: A prospective study was performed in pregnant women admitted to maternal-fetal intensive care unit in Seoul National University Bundang Hospital from June to August 2023. Twenty one patients were enrolled (9 singleton and 12 twin pregnancies) and underwent BIA at the admission. Maternal obstetric baseline characteristics were reviewed.

Results: There was no statistical difference between singleton and twin pregnancies in terms of maternal age and gestational ages at the tests and other obstetric complications. The phase angle was significantly lower in twin pregnancies than in singleton pregnancies (5.1° vs. 6.2°, p = 0.007) and the difference was more distinct in the lower extremities (right; left; both; p < 0.05). The mean values of total body water (TBW), intracellular water (ICW), and extracellular water (ECW) measured in the whole body, trunk, and extremities were not statistically different between the twin and singleton pregnancy groups; however, the ratio of ECW to TBW was significantly higher in twin pregnancies than in singleton pregnancies (0.40 vs. 0.39, p = 0.001). All ECW/TBW ratios measured in the trunk and extremities presented with the same results as ECW/TBW ratios measured in the whole body (all: p < 0.05). The T-score was significantly higher in the twin group than in the singleton group (4.4 vs. 1.2, p = 0.001).

Conclusions: Twin pregnancies had a lower phase angle and higher ECW/TBW ratio compared to singleton pregnancies.