First trimester aneuploidy antenatal screening use BHCG as a marker for trisomy 18 and 21 in conjunction with other parameters and ultrasound imaging results.
In uncomplicated intrauterine pregnancies, typically levels double exponentially in the first 8 weeks of gestation, peaking at 10 weeks and decreasing until the 16th week of pregnancy where they remain constant until term.
Healthy non pregnant women have serum levels <5 IU/L.
For diagnostic purposes, hCG results should always be used in conjunction with other data, eg, patient medical history, symptoms, results of other tests, clinical impressions, etc. This assay is used for the detection of pregnancy only.
