Objective: To investigate the relationship between unexplained elevated second-trimester free ß-human chorionic gonadotropin (ß-hCG) levels and pregnancy complications as well as adverse pregnancy outcomes. Methods: The study cohort comprised 2,110 non-smoking women with chromosomal and structurally normal fetuses at low-risk for both Down’s syndrome (risk !1:250) and neural tube defects (maternal serum ·-fetoprotein !2.0 MoM). A free ß-hCG value of 62.0 MoM was used to define the populations with elevated levels of free ß-hCG. Descriptive statistics, ¯2 test, Fisher’s exact test, and logistic regression analysis were used for statistical analysis, and p ! 0.05 was considered statistically significant. Results: The mean maternal age of the study group was significantly lower than in controls (27.9 B 4.3 and 30.6 B 5.1 years, respectively, p ! 0.05), while the proportion of primigravidas was significantly higher compared to that of controls (p ! 0.05). After adjustment of the 2 groups according to maternal age and parity, we observed an increased incidence of preeclampsia among women with elevated free ß-hCG levels in relation to controls (p ! 0.05). However, a logistic regression analysis demonstrated that the free ß-hCG level was not a predictor of the occurrence of preeclampsia. No significant relationship was found with the incidence of gestational diabetes, oligohydramnios, polyhydramnios, pregnancy-related hypertension, intrauterine growth retardation, preterm delivery, spontaneous abortion and stillbirths (p 1 0.05).