A longitudinal study of maternal cardiovascular function from preconception to the postpartum period.

OBJECTIVE: Our objective was to investigate the extent of changes in maternal cardiovascular function, lipids and renal function during normal pregnancy from preconception to postpartum period.
METHODS: In this prospective study of 54 normal pregnancies, detailed hemodynamics were performed preconception, at 6, 23 and 33 weeks during pregnancy and 16 weeks postpartum.
RESULTS: Although the greatest reduction of blood pressures (BPs) and augmentation index occurred in early pregnancy (Δbrachial systolic: 4 ± 7  mmHg, Δcentral systolic: 7 ± 7  mmHg; P < 0.001), the peripheral vascular resistance reached a nadir (Δ: 222 ± 215 dynes.s.cm; P < 0.001) by the second trimester. The greatest increase in cardiac output occurred by the second trimester (Δ: 0.6 ± 1 l/min, P < 0.001), whereas the heart rate increased maximally by the third trimester (Δ: 13 ± 11  bpm; P = 0.001). The unadjusted aortic pulse wave velocity decreased in the second trimester (P < 0.001), however, when adjusted for mean arterial pressure this was not significant (P = 0.06). BPs were lower (Δ brachial systolic: 5 ± 8  mmHg; P < 0.001) and augmentation index higher (Δ: 2.5 ± 7%; P = 0.01) postpartum than preconception. The cholesterol:high-density lipoprotein ratio, serum low density lipoprotein and serum creatinine all fell (P < 0.001) in the first trimester.
CONCLUSION: We have shown that normal pregnancy, irrespective of parity, is associated with significant changes commencing very early in pregnancy, continuing throughout pregnancy, and some of these changes persisted postpartum. Therefore, first trimester or postpartum baselines will underestimate the true extent of pregnancy-related changes. Prospective studies of cardiovascular function from preconception to postpartum will provide more reliable estimates of the influence of cardiovascular maladaptation during pregnancy complications and their effect on longer term cardiovascular function.