Correlation between central and uterine haemodynamics in hypertensive disorders of pregnancy.

INTRODUCTION: Pregnancies affected by hypertensive disorders (HDP) have increased uterine artery pulsatility index (UTA PI) compared to healthy pregnancies. De novo increases in UTA PI in the third trimester have been reported, making these changes less attributable to inadequate spiral artery invasion, which is typically recognised as an early pregnancy phenomenon. Women with HDP are also known to have lower cardiac output and increased systemic vascular resistance. The aim of this study was to investigate the relationship between central and uterine haemodynamics, in both HDP and uncomplicated pregnancies.

METHODS: This was a prospective study in control pregnancies and those with HDP. Paired measurements of maternal haemodynamics, using a non-invasive device (USCOM-1A®), and uterine artery Doppler were performed in the third trimester.

RESULTS: There were 231 women in the HDP group and 378 women in the control group. Women with preterm HDP had significantly lower cardiac output (median (IQR) 6.0 (5.1-7.2) vs. 6.6 (5.8-7.5) L/min, p=0.002) and higher systemic vascular resistance (median (IQR) 1394 (1189-1670) vs. 1063 (915-1222) dynes-sec-cm5 , p<0.001) and UTA PI (median (IQR) 1.0 (0.75-1.4) vs. 0.67 (0.58-0.83) p<0.001) compared to controls. Conversely, in women with term HDP, there were no significant differences in heart rate, cardiac output or UTA compared to controls (all P>0.05), while systemic vascular resistance was significantly higher (median (IQR) 1315 (1099-1527) vs 1063 (915-1222) dynes-sec-cm5 , p<0.001). In multiple regression analysis, heart rate, mean arterial pressure and stroke volume were significantly associated with the mean UTA PI (all p<0.001).

CONCLUSION: Differences observed in the uterine artery resistance in the third trimester of pregnancy are mirrored in the central maternal haemodynamic parameters. Late pregnancy differences in the utero-placental circulation in preterm and term HDP are an index of maternal cardiovascular function rather than being related to inadequate spiral artery modelling and impaired placentation. This article is protected by copyright. All rights reserved.