- Background Elevated midtrimester human chorionic gonadotropin (hCG) is associated with adverse maternal and perinatal outcome. The aims of the study were to evaluate the association between elevated hCG and fetal arterial circulation and to determine the relationship between maternal and perinatal complications and elevated hCG. Methods Pulsatility indices (PI) of middle cerebral artery (MCA) and umbilical artery (UA) were determined prospectively in 72 consecutive patients with abnormal maternal serum hCG (> 2.5 MoM). Each patient had between two to four US scans during pregnancy. Patients with known structural or chromosomal anomalies were excluded from the study. Results Out of 72 women with hCG > 2.5 MoM, 48% (35/72) had hCG > 3.5 and 24% (17/72) had. hCG levels > 4.5 MoM. MCA PI was lower in women with hCG > 4.5 MoM between 28 and 36 wks' gestation, but not between 18 and 27 wks' gestation (fig). No differences of MCA PI were found when the cutoff point of hCG was 3.5. PI of the UA was not different between the groups. Women with hCG levels > 4.5 MoM had a higher prevalence of PIH and preeclampsia, preterm deliveries and cesarean sections in comparison to women with hCG < 4.5 MoM. Birthweight was lower and the rate of Apgar score < 7 was higher. No differences were not found with cutoff 3.5MoM. Conclusions Maternal midtrimester hCG > 4.5 mom is associated with cerebral blood flow redistribution and with higher rates of maternal and perinatal complications in comparison to maternal hCG of 2.5–4.5 MoM.