Severity of pulmonary hypertension and pregnancy outcomes: newer insights from the M-PAC registry

Abstract Background Pregnancy outcomes in women with pulmonary hypertension remain suboptimal. Pregnant women with pulmonary hypertension (PH) are placed in the modified WHO category IV, regardless of the severity or etiology of PH. Earlier studies have indicated that pregnancy outcomes may differ based on the etiology, with more favourable outcomes observed with PH related to left to right shunts. However, it is possible that the pregnancy outcomes may vary based on the severity of PH also. Purpose To analyse pregnancy outcomes in women with PH and investigate differences based on disease severity. Methods M-PAC Registry, is a single center prospective study of pregnancies in women with heart diseases, conducted between July 2016 and December 2019 in a low-and middle-income country from South Asia, whose methodology and outcomes have been published(1). The current study analysed pregnancies with PH enrolled in the M-PAC registry. The tricuspid regurgitation velocity obtained during transthoracic echocardiography, was used to estimate right ventricular systolic pressure (RVSP). Based on the estimated RVSP, PH was classified into three groups; mild (36-45 mm of Hg), moderate (46-64 mm of Hg) and severe (≥ 65 mm of Hg). The differences in the maternal and foetal outcomes among the groups were analysed. Results Of the 1029 pregnancies complicated by heart disease enrolled in the M-PAC registry, 352(34.2%)had PH. Among these 352 pregnancies, 186(52.8%) had mild, 73 (20.7%) had moderate and 93 (26.5%) had severe PH. Adverse maternal cardiac events occurred in 77 pregnancies (21.8%), with heart failure in 53(15.1%) and mortality in 10(2.8%). The composite adverse foetal event rate was 38.6%, foetal loss at 9.7%, low birth weight at 28.9%, and preterm labour at 7.1%. The mean (±standard deviation) RVSP was higher in pregnancies with adverse maternal outcome (58.81±16.9 vs 51.16±15.9; P < 0.001) or adverse foetal outcome (58.10±17.3 vs 49.52±14.9; P < 0.001)compared to those without. When comparing the three groups, pregnancies with mild PH exhibited significantly lower rates of adverse maternal and fetal events compared to those with severe and moderate PH (Fig-1 and Table-1). Mild PH was associated with outcomes similar to those without PH in the M-PAC registry. Conclusion The severity of PH significantly correlated with the adverse pregnancy outcomes. Women with mild PH tend to experience pregnancy outcomes comparable to those without PH, suggesting that pregnancy should not be deemed contraindicated in this subgroup. Therefore, re-evaluation of the placement of PH within the modified World Health Organization (mWHO) classification is warranted, considering the severity of PH.Figure 1:Pregnancy Outcomes & PH SeverityTable-1 PH Severity & Pregnacny Outcomes