Delayed luteo–placental shift of progesterone production in IVF pregnancy

Objective : To observe absolute and relative levels of progesterone, 17α‐hydroxyprogesterone (17‐OHP) and human chorionic gonadotrophin (hCG) in in vitro fertilization (IVF) pregnancies after withdrawal of luteal support. Method : Single blood samples were obtained from 41 pregnant women following IVF treatment and 43 normal pregnant women at various weeks gestation within the first trimester. Progesterone, 17‐OHP and hCG were measured by immunoassay. Results : Serum levels of progesterone, but not of hCG, in IVF pregnancies were significantly greater than in normal pregnancies up to 8 weeks post‐conception, despite discontinuing luteal support 2 weeks after conception. The ratio of progesterone to 17‐OHP, a predominantly ovarian product, in normal pregnancies rose between 4 and 9 weeks but did not change over the same period in IVF pregnancies. Conclusion : The luteal contribution to maternal serum levels of progesterone is much higher in IVF pregnancies compared with normal pregnancies. This is sustained throughout the first trimester without the need for luteal support and obscures the placental contribution of progesterone for much longer than in normal pregnancies. Progesterone or hCG supplements may therefore be unnecessary in IVF pregnancy.