Pregnancy Test

 

The most common pregnancy test measures the beta subunit of human chorionic gonadotropin (β-hCG). This hormone is produced by the placental trophoblastic cells to maintain progesterone production of the corpus luteum.

 

β-hCG becomes positive in the serum 9 days following conception and 14 days in the urine.

It doubles every 48 hours during early pregnancy, peaking at 100,000 mIU/ml at 8-10 weeks gestation, and falls before plateauing until delivery.

Less than expected values suggest ectopic pregnancy, abortion, or the wrong dates.

Higher than expected values can occur with multiple gestation, molar pregnancy, trisomy 21, or the wrong dates.

 

β-hCG is thought to be responsible for many of the symptoms of pregnancy, including morning sickness.