Cardiovascular function in normal pregnancy and fetal growth

Abstract

Background: Pregnancy is a challenge to a woman’s cardiovascular system, and extensive haemodynamic changes are required for optimal utero-placental circulation and fetal growth. The aim of this thesis was firstly to examine different aspects of vascular function in the same women longitudinally during normal pregnancy, and secondly to explore whether there is an association between maternal cardiovascular function, placental function, and fetal growth.

Methods and Main Results: Study I and II were prospective cohort studies investigating cardiovascular structure and function in 52 healthy women longitudinally at 14, 24 and 34 weeks gestation, and nine months postpartum. In Study I, brachial and central blood pressure, pulse-wave velocity, augmentation index, common carotid artery structure and endothelial function in the brachial artery (FMD) and in the forearm skin microcirculation was assessed. The study found that brachial and central blood pressure initially decreased and then increased. FMD and endothelium dependent microvascular reactivity increased during pregnancy. Pulse wave velocity and augmentation index decreased, reaching a nadir in the second trimester. In Study II, cardiac function, myocardial mechano-energetic efficiency (MEE), and ventricular-arterial coupling (VAC) were measured. Left ventricular (LV) mass and cardiac output (CO) increased during pregnancy. LV diastolic function decreased but MEE and VAC maintained during pregnancy. There was a positive correlation between first and second trimester heart rate, and birth weight centile. Study III was a cross-sectional study (n=56) investigating the association between first trimester vascular function and birth weight centile. Maternal first trimester vascular reactivity in the brachial artery, and in the forearm skin microcirculation, related positively to birth weight centile. Study IV was a cross-sectional study (n=53) investigating the association between levels of circulating maternal pregnancy-associated plasma protein A (PAPP-A), and first trimester maternal vascular function. PAPP-A correlated positively to first trimester maternal skin microvascular endothelial function index.

Conclusions: During normal pregnancy, there were profound structural and functional changes throughout the cardiovascular tree. These changes are probably necessary for sufficient fetal growth, which is supported by the observed relation between maternal heart rate, vascular vasodilator capacity, and fetal growth. Given that first trimester PAPP-A levels relate to placental function, our results suggest that placental function can be reflected by first trimester endothelium dependent skin microvascular reactivity.