Biochemical screening for aneuploidy in ovum donor pregnancies.

Objective: The purpose of this study was to compare the screening efficacy for aneuploidy detection in ovum donor pregnancies with the use of either the age of the ovum donor or the ovum recipient.

Study Design: Second-trimester biochemical screening for aneuploidy with alpha-fetoprotein, unconjugated estriol, and human chorionic gonadotropin was performed on maternal serum samples that were submitted prospectively from singleton ovum donor pregnancies. The calculation of aneuploidy risks were performed separately with the age of the ovum donor or the ovum recipient. Risks of >1 in 295 and >1 in 100 were used as cutoff values for the identification of screen-positive pregnancies for Down syndrome and trisomy 18, respectively.

Results: Samples from 93 ovum donor pregnancies were identified. The mean ages of the ovum donors and recipients were 27 years (range 20-38.5 years) and 43.6 years (range, 25.9-54.3 years), respectively. When the age of the ovum donor was used in the determination of aneuploidy risk, there were 9 screenpositive pregnancies (9.7%), whereas the use of the age of the ovum recipient resulted in 76 screen-positive pregnancies (82%). With the use of the McNemar test for paired observations, the proportion of screenpositive pregnancies with the age of the ovum donor (9.7%) compared with the age of the ovum recipient (82%) was statistically significant (P <.0001). The odds of being affected, given a positive result, were 1 in 9 (11%) with the age of the ovum recipient and 1 in 76 (1.3%) with the age of the ovum donor. The only fetus with aneuploidy (trisomy 18) was identified as being screen positive in both the ovum donor and ovum recipient calculations.

Conclusion: In ovum donor pregnancy aneuploidy risk calculations, the use of the age of the ovum donor instead of the ovum recipient reduces the false-positive rate and improves screening efficacy.