Maternal and Fetal Hemodynamic Adaptations to Pregnancy and Clinical Outcomes in Maternal Cardiac Disease

Background: Although insufficient maternal cardiac output (CO) has been implicated in poor outcomes in mothers with heart disease (HD), maternal-fetal interactions remain incompletely understood. We sought to quantify maternal-fetal hemodynamics with the use of magnetic resonance imaging (MRI) and explore their relationship with adverse events. Methods: Pregnant women with moderate or severe HD (n = 22; mean age 32 ± 5 years) were compared with healthy control women (n = 21; 34 ± 3 years). An MRI was performed during the third trimester at peak output (maternal-fetal) and 6 months postpartum with return of maternal hemodynamics to baseline (reference). Phase-contrast MRI was used for flow quantification and was combined with T1/T2 relaxometry for derivation of fetal oxygen delivery/consumption. Results: Third-trimester CO and cardiac index (CI) measurements were similar in HD and control groups (CO 7.2 ± 1.5 vs 7.3 ± 1.6 L/min, P = 0.79; CI 4.0 ± 0.7 vs 4.3 ± 0.7 L/min/m,² P = 0.28). However, the magnitude of CO/CI increase (Δ, peak pregnancy − reference) in the HD group exceeded that in the control group (CO 46 ± 24% vs 27 ± 16% [P = 0.007]; CI 51 ± 28% vs 28 ± 17% [P = 0.005]). Fetal growth and oxygen delivery/consumption were similar between groups. Adverse cardiovascular outcomes (nonmutually exclusive) in 6 HD women included arrhythmia (n = 4), heart failure (n = 2), and hypertensive disorder of pregnancy (n = 1); premature delivery was observed in 2 of these women. The odds of a maternal cardiovascular event were inversely associated with peak CI (odds ratio 0.10, 95% confidence interval 0.001-0.86; P = 0.04) and Δ,CI (0.02, 0.001-0.71; P = 0.03). Conclusions: Maternal-fetal hemodynamics can be well characterised in pregnancy with the use of MRI. Impaired adaptation to pregnancy in women with HD appears to be associated with development of adverse outcomes of pregnancy.