MATERNAL SERUM-FREE ALPHA-HUMAN AND FREE BETA-HUMAN CHORIONIC-GONADOTROPIN IN PREGNANCIES WITH INSULIN-DEPENDENT DIABETES-MELLITUS - IMPLICATIONS FOR SCREENING FOR DOWNS-SYNDROME

A study was performed to investigate the concentrations of the alpha a nd beta free sub-units of human chorionic gonadotrophin (free alpha-hC G and free beta-hCG) in maternal serum between 15 and 22 weeks of preg nancy in 126 pregnancies among 92 women with insulin-dependent diabete s mellitus (IDDM). Each IDDM pregnancy was matched with two control si ngleton pregnancies for gestational age (same completed week) and dura tion of sample storage (same calendar quarter). The median free alpha- hCG lever in the IDDM pregnancies was 0.86 multiples of the median (MO M) for pregnancies without IDDM at the same gestational age (P<0.002) (95 per cent confidence interval 0.80-0.94). The corresponding free be ta-hCG level was 0.96 MOM (95 per cent confidence interval 0.85-1.09). These results enable free alpha-hCG values to be adjusted so that ant enatal screening for Down's syndrome can be performed using this marke r in IDDM pregnancies as well as in non-diabetic pregnancies.