Abstract

Objective Twin pregnancies are at increased risk of developing hypertensive disorders of pregnancy (HDP) compared with singleton pregnancies, resulting in a substantially higher rate of maternal and perinatal complications. The strain caused by twin pregnancy on the maternal cardiovascular system has not been studied extensively. The objective of this study was to evaluate the changes in maternal cardiac morphology and diastolic function in a cohort of women with normotensive and those with hypertensive twin pregnancies. Methods This was a cross-sectional study conducted at a tertiary referral university center. Women with singleton or twin pregnancy were enrolled prospectively to undergo maternal transthoracic echocardiography throughout pregnancy. Multiples of the median (MoM) were calculated for each index using a reference group of uncomplicated singleton pregnancies (n = 411) in order to adjust for changes associated with gestational age. Cardiac findings were indexed for body surface area and compared among normotensive twin pregnancies, singleton pregnancies complicated by HDP and twin pregnancies complicated by HDP. Results The total cohort included 119 HDP singleton pregnancies, 52 normotensive twin pregnancies and 24 HDP twin pregnancies. Left ventricular mass index (LVMi) MoM (median (interquartile range)) did not differ between singleton pregnancies complicated by HDP and normotensive twin pregnancies, but was significantly higher in HDP twin compared with HDP singleton pregnancies (1.31 (1.08–1.53) vs 1.17 (0.98–1.35), P = 0.032). Two diastolic indices, left atrial volume index MoM (1.12 (0.66–1.38) vs 0.65 (0.55–0.84), P = 0.003) and E/e′ MoM (1.29 (1.09–1.54) vs 0.99 (0.99–1.02), P = 0.036), were significantly higher in HDP twin compared with normotensive twin pregnancies. In normotensive twin compared with HDP singleton pregnancies, stroke volume index (SVi) MoM was higher (1.20 (1.03–1.36) vs 1.00 (0.81–1.15), P = 0.004) and total vascular resistance index (TVRi) was lower (0.73 (0.70–0.86) vs 1.29 (1.04–1.56), P < 0.0001). In contrast, SVi MoM was lower (1.10 (1.02–1.35) vs 1.20 (1.03–1.36), P = 0.018) and TVRi was higher (1.00 (0.88–1.31) vs 0.73 (0.70–0.86), P = 0.029) in HDP twin compared with normotensive twin pregnancies. Conclusion The maternal cardiovascular system is altered severely in twin pregnancy with or without HDP. Despite the low total vascular resistance, cardiac changes in normotensive twin pregnancies are comparable to those seen in singleton pregnancies complicated by HDP, reflecting the high cardiovascular demand imposed by twin pregnancy.