OP02.01: Endometriosis and impaired placentation: longitudinal cohort study estimating uterine arteries Doppler trajectories in singleton pregnancies

The correlation between endometriosis and adverse obstetric outcomes is still under debate. A defective deep placentation has been proposed as potential pathogenic mechanisms. The present study aimed to investigate the impact of endometriosis on uterine arteries pulsatility index (UtA-PI) during pregnancy. Prospective, longitudinal cohort study carried out from 2016 to 2021 at IRCSS San Raffaele Hospital, Milan. Pregnant women with endometriosis and matched healthy controls with a 1:2 ratio were included (n=140). Ultrasound measurements at 11–34 weeks were performed according to ISUOG guidelines. Primary outcome was the comparison of mean UtA-PIs between endometriosis and controls. Secondary outcomes were 1st trimester serum biomarkers, pregnancy and perinatal complications. A multilevel linear mixed model (LMM) analysis of 262 Doppler observations was performed. No significant differences were observed neither in mean/z-score UtA-PIs nor in 1st trimester serum biomarkers. Higher yet not significant proportions of small for gestational age (SGA) fetuses (8.5% vs. 3.2%) and neonates (14.9% vs. 9.7%) were observed in endometriosis. A significant effect of gestational age (GA) modelled with a quadratic polynomial was described in the LMM (p = .007). The presence of endometriosis had a negative yet not significant effect, although the significant interaction term between group and GA (p = .018) was suggestive for a more progressive decrease of UtA-PI in cases during gestation. UtA-PI values were 8.9% lower in patients who conceived by ART (p = .001) and type of conception retained a significant effect for every passing week of gestation (p = .021). The prevalence of gestational diabetes (p = .007), gestational hypothyroidism (p = .002) and preterm birth (p = .03) was higher in endometriosis. Endometriosis does not seem to be associated with a clinically measurable impaired placental perfusion, suggesting that other mechanisms may be involved in the pathogenesis of abnormal pregnancy outcomes.