First-trimester screening for Down syndrome in singleton pregnancies achieved by intrauterine insemination.

PURPOSE: To evaluate whether achieving a singleton pregnancy by IUI affects the results of first-trimester screening for Down syndrome compared to naturally conceived pregnancy.

METHODS

Forty-nine IUI and 3059 naturally conceived singleton pregnancies were included in the study. Ovulation in IUI pregnancies was induced by clomiphene and human menopausal gonadotropin. Progesterone was given after insemination for 2 weeks. Down syndrome screening was performed using a combination of maternal age, fetal nuchal translucency, and maternal serum concentrations of free beta-hCG and PAPP-A during the period of 10-14 weeks' gestation.

RESULTS

In IUI pregnancies, nuchal translucency thickness and the levels of PAPP-A were significantly higher. The values of free beta-hCG were not statistically different between the two groups. The screen-positive rate in IUI pregnancies was significantly higher (14.3% vs. 7.1%).

CONCLUSIONS

Singleton pregnancies achieved by IUI have a higher screen-positive rate. Not only elder maternal age but also exogenous hormones given during the process of ovulation induction and after conception may play an important factor influencing positive screening results.