First-trimester screening

A combination of a special ultrasound test (measuring nuchal translucency and possibly other factors such as nasal bone size) and a biochemical analysis of PAPP-A (Pregnancy-associated plasma protein A) and free β-hCG (ß-chain of the human chorionic gonadotropin) in the mother’s blood serum. The test can be performed between weeks 11+0 and 14+0 of a pregnancy to determine the likelihood of fetal chromosomal disorders (e.g. trisomy 21).