Levels of human chorionic gonadotropin in healthy pregnant Nigeria women.

Serum levels of human chorionic gonadotropin (hCG) were measured in venous blood samples of 100 healthy pregnant Nigerian women from weeks 5 to 40, using a batasubunit, hCG--specific radioimmunoassay. By week 5 hCG concentration was 3.39 +/- 2.35 Iu/ml (mean +/- SEM). An exponential rise occurred from week 5 to 8, during which period a direct relationship was observed between serum hCG levels and the gestational age (r2 = 0.996; p less than 0.001). The calculated mean doubling-time of hCG concentration, during this period of exponential increase was 5.08 days. A peak hCG concentration of 62.61 +/- 0.81 Iu/ml was attained at week 8, followed by a progressive decrease in concentration from week 9. The decrease in concentration reached a nadir by week 17 with a value of 4.77 +/- 2.48 Iu/ml. Between weeks 17 and 40 no significant difference in weekly mean values was detected. The respective mean values of hCG for the three trimesters were 25.79 Iu/ml for the first (n = 32), 8.91 Iu/ml for the second (n = 86) and 5.18 Iu/ml for the third (n = 110). There was no secondary peak of hcG concentration during the third trimester. The significance of these data is discussed.