Detection of hydatidiform mole in maternal serum screening programmes for Down's syndrome.

Objective: To determine how frequently hydatidiform mole will be detected in a maternal serum Down's syndrome screening programme.

Methods: Affected pregnancies were identified using a national register. Unconjugated oestriol (uE3) and human chorionic gonadotrophin (hCG) were measured in stored serum samples and alphafetoprotein (AFP) levels were available from previous neural tube defect screening at 15-20 weeks gestation. Methods: Ten pregnancies with a complete mole (i.e., hydropic placenta without a fetus), nine with stored serum samples and one with an AFP level only.

Results: The median values were 0.08, 0.13 and 1.83 multiples of the normal median for AFP, uE3 and hCG respectively. Six out of nine (67%) tested for all three markers had a high risk of Down's syndrome given maternal age and the marker levels.

Conclusions: Many molar pregnancies that have not presented clinically before 15 weeks will be detected through Down's syndrome screening.