Maternal serum screening for fetal Down syndrome using alpha-fetoprotein, human chorionic gonadotrophin, and unconjugated estriol in adolescents

Study Objective: To learn whether accuracy and false-positive rate of our maternal serum screening program for fetal Down syndrome differed in adolescents compared with adults. In addition, we studied the degree to which overestimated gestational age accounted for screen-positive results and the rate at which amniocentesis was elected by patients in different age groups. Design: Maternal serum screening using human chorionic gonadotropin (hCG), alpha-fetoprotein, unconjugated estriol and age was offered for fetal Down syndrome to all women between 15 and 20 weeks gestation who were less than or equal to 35 years of age at date of delivery. Women found to have a risk for fetal Down syndrome of ≥1:274 were considered screen-positive. If gestational age was confirmed by ultrasound, then genetic counseling and amniocentesis were offered. Results: Of 10,627 women screened, 2,237 (21.1% of population screened) were between ages 12 and 19 years. Of these adolescents, 175 (7.5%) were screen positive. Of these 175, 114 (65.1%) were found by ultrasonographic examination to have overestimated gestational age, and compared with adult women (ages 20-34 years); this was statistically significant (p < 0.003). Of the remaining 61 patients, 13 (21.3%) were lost to follow-up. The remaining 48 were offered genetic counseling and amniocentesis, of whom 38 (79.2%) elected to have amniocentesis. In the total population screened, four of seven Down syndrome cases were detected, one in a 19-year-old. In the three cases not detected, one was in a 19-year-old and one was in a 22-year-old. Conclusions: Fetal Down syndrome screening may not be as sensitive in younger women as in older women, however, counseling and management in adolescents need not differ from that of adults. Appropriate diagnostic procedures should be offered to all women at increased risk for fetal Down syndrome.