The predictive value of hCG β subunit levels in pregnancies achieved by in vitro fertilization and embryo transfer: an international collaborative study

Serial human chorionic gonadotropin (hCG) β subunit measurements of 300 pregnancies achieved by in vitro fertilization (IVF) were obtained by 15 IVF centers worldwide. Hormonal curves were established for 164 normal singleton pregnancies, 25 normal multiple gestations, 60 chemical pregnancies, 41 first-trimester spontaneous abortions, and 10 ectopic pregnancies. In comparison to the normal singleton pregnancy curve, chemical pregnancies and spontaneous abortions showed statistically lower hCG levels. hCG levels of ectopic pregnancies, compared with normal singleton gestations, were lower from days 7 to 14. It is concluded that β-hCG determinations of in vitro fertilized pregnancies allow pregnancy diagnosis as early as 7 to 9days after embryo transfer (ET) and will permit early discrimination between normal and abnormal IVF pregnancies. A single β-hCG determination on day 9 after ET may discriminate chemical, ectopic pregnancy or impending miscarriage from a normal gestation. An hCG determination on day 17 will predict early normal development of an IVF pregnancy.