Fetal heart rate and nuchal translucency in detecting chromosomal abnormalities other than Down syndrome.

OBJECTIVE

To evaluate whether the combined use of fetal heart rate (FHR) and nuchal translucency measurements would be useful in the prediction of fetal chromosomal abnormalities at 10-13 weeks' gestation.

METHODS

In a prospective study, 1053 (553 reported previously) consecutive singleton pregnancies between 10 and 13 weeks' gestation underwent chorionic villus sampling at our institution. Fetal heart rate and fetal nuchal translucency thickness were measured immediately before the invasive procedure.

RESULTS

Thirty-five abnormal karyotypes were diagnosed, including 17 trisomy 21, seven trisomy 18, one trisomy 13, one trisomy 9, four unbalanced translocation, two Klinefelter syndrome, one Turner syndrome, one deletion of chromosome 18, and one true mosaicism. Using 95% of normal ranges as the cutoff for both measurements, the detection rate for all chromosomal anomalies was 77.1%, with a false-positive rate (1-specificity) of 7.7%, a positive predictive value of 25.7%, and a negative predictive value of 99.2%. Fetal heart rate improved the sensitivity of nuchal thickness in trisomies 21 and 18 (from 62.5% to 75%) and was particularly useful to detect other chromosomal anomalies (from 27.2% to 81.8%).

CONCLUSION

Our findings suggest that there is an added role of FHR in ultrasound screening of chromosomal abnormalities, specifically for those other than trisomy 21 and 18. The value of a single measurement of fetal heart rate for screening purposes needs to be confirmed by further investigation in a low-risk population.