The umbilical artery pulsatility index in the first trimester: is there an association with increased nuchal translucency or chromosomal abnormality?

Objective The aim of this study was to examine the possible association between umbilical artery pulsatility index (PI) at 10–14 weeks of gestation and either increased fetal nuchal translucency (NT) or fetal chromosomal abnormality. Design This was a prospective study of women undergoing chorionic villus sampling (CVS). Subjects A total of 458 women undergoing CVS were studied; in 418 cases the karyotype was normal and in 19 cases fetal trisomy 21 was identified. Methods Data from the women with a normal fetal karyotype and in whom the NT was also normal were used to calculate reference ranges for the umbilical artery PI. Associations were sought between umbilical artery PI and increased NT and between the PI and fetal trisomy 21. Results We found no association between umbilical artery PI and NT, nor was there a difference in the PI between chromosomally normal pregnancies and those with fetal trisomy 21. Conclusion The results suggest that fetoplacental vascular resistance per se does not contribute to increased NT and that measurement of the umbilical artery PI does not contribute to the first-trimester detection of fetal trisomy 21.