Unconjugated Estriol
Estriol comprises 90% of the estrogens circulating in maternal blood in normal pregnancies, reflecting estriol secretion by fetal liver and by placenta. Unconjugated estriol level is good indicator of fetal well-being and placental function. The determination of unconjugated estriol is intended to be used, in conjunction with other screening markers (hCG, AFP, …), in risk assessment of Down syndrome (trisomy 21) in the 2nd trimester of pregnancy.