First-trimester screening in triplets.

OBJECTIVE

The purpose of this study was to determine the performance of Down syndrome screening in triplet pregnancy.

STUDY

DESIGN

Nuchal translucency (NT; n = 794), nasal bone (n = 219), and biochemistry (n = 198) were evaluated in triplet pregnancy. Screening performance was evaluated with the use of delta and Gaussian models.

RESULTS

The median multiples of the median values for free beta human chorionic gonadotropin and pregnancy-associated plasma protein A were 2.86 and 3.48, respectively. A significant correlation in delta NT within pregnancy was observed (0.46-0.68). The modeled false-positive rates were 11.7%, 7.4%, and 8.9% with the delta model and 11.9%, 6.6%, and 12.0% with the Gaussian model for NT, NT + nasal bone, and NT + biochemistry. Based on simulation, the detection rate at 12 weeks' gestation was 78%, 93%, and 80% for NT, NT + nasal bone, and NT + biochemistry at a 10% false-positive rate using either the delta or Gaussian models.

CONCLUSION

In triplet pregnancy, the addition of nasal bone lowers the false-positive rate of nuchal translucency screening. More data are required on the effectiveness of biochemistry.