Figure 8.Circulating maternal steroid hormone levels throughout early pregnancy. The first-trimester relationship of these steroid hormones to human chorionic gonadotropin (hCG) is shown.ProgestogensProgesterone o–o–o- 17-a-hydroxyprogesterone -Δ-Δ-Δ-Estrogens17- β -estradiol – Ÿ – Ÿ – Ÿ Estriol -o-o-o- Estrone -x-x-x-Human chorionic gonadotropin (hCG)-Δ-Δ-Δ- (From ref. 89, with permission)