Reference values of nuchal fold thickness in an Iranian population sample

Considering that ethnicity and gestational age (GA) could a?ect the value of nuchal fold thickness (NFT) in mid?trimester, we aimed to determine the reference intervals of NFT values for each gestational week from 16 to 24 weeks of pregnancy among a group of Iranian pregnant women. In this cross?sectional study, medical fles of pregnant women who underwent fetal anomaly scanning at 16–24 weeks of gestation were reviewed and the following data were extracted: GA, value of NFT, value of nuchal translucency (NT) in their previous ultrasound study, if available, and head circumference (HC). Te 5th, 25th, 50th, 75th, and 95th percentiles of NFT for each gestational week were determined. Te association between NFT and HC, GA, and NT were also determined. Medical fles of 882 pregnant women were studied. Te expected 95th percentile value of NFT between 16th and 24th weeks of gestation ranged from 4 mm to 5.9 mm. Te mean (standard deviation) of NFT increased with GA from 2.67 (0.90) mm at 16th weeks to 4.69 (0.71) mm at 24th weeks. Tere was a signifcant positive association between NFT and GA (? = 1.11, P < 0.001), HC (? = 0.21, P < 0.001), and NT (? = 0.351, P < 0.001). Te fndings of this study revealed that before the 20th week of gestation, the appropriate cuto? value of NFT is 5 mm, and for 21st to 24th weeks, the proper cuto? is 6 mm. However, for providing more conclusive results, further studies with larger sample size and considering the impact of other in?uencing variables are recommended.