First-trimester angiopoietin-2: relationships with maternal and placental characteristics

Angiopoietin-2 (Ang-2), synthesized by endothelial cells, is a marker of placental vascular remodeling. Ang-2 is expressed in the first trimester, and levels may therefore correlate to other parameters of placental vascular development. The aim of this study was to evaluate the relationships between Ang-2 and other maternal/placental factors in the first trimester. This was a prospective observational study of women presenting for first-trimester screening at 11 + 0 to 13 + 6 weeks. Consenting women underwent an ultrasound, physical examination, and blood draw. Maternal serum Ang-2 levels were determined using enzyme-linked immunosorbent assay. Results were evaluated with relation to maternal age, parity, race, body mass index (BMI), mean arterial pressure (MAP), smoking/caffeine use, and parameters of placental blood flow resistance. In 111 consecutive patients, serum Ang-2 ranged from 0.6 to 10.9 ng/mL. Ang-2 levels were unrelated to maternal age, race, parity, smoking, and caffeine intake. Significant negative correlations were observed with BMI (Pearson's R = -0.325; P < 0.0001) and MAP (Pearson's R = -0.287; P = 0.002). Ang-2 levels did not correlate with gestational age (Spearman's rho, 0.064; P = 0.5058), but a significant positive correlation with the crown-rump length was observed (Spearman's rho, 0.261; P = 0.006). Neither uterine artery notching nor umbilical artery Doppler parameters correlated with Ang-2 levels. We concluded that Ang-2 as a marker of placental angiogenesis has significant relationships with maternal risk factors associated with abnormal placental development.