To investigate prenatal diagnosis value of increased nuchal translucency (NT) thickness and absence of nasal bone of fetal in first trimester.

From October 2016 to April 2019, a total of 488 cases of singleton pregnancy fetus who were screened by ultrasound to confirm the increased NT thickness and/or absence of nasal bone in first trimester in Dongguan People′s Hospital were selected as research subjects. The clinical date of pregnant women of fetus were analyzed retrospectively.Chi-square test was used to compare the incidence of chromosomal abnormalities under 5 ultrasound conditions, including isolated increased NT thickness, isolated absence of nasal bone, increased NT thickness + absence of nasal bone, increased NT thickness + other structure abnormalities, and increased NT thickness + absence of nasal bone + other structure abnormalities. The procedure followed in this study was consistent with World Medical Association Declaration of Helsinki revised in 2013.

①The incidence of chromosomal abnormalities of fetuses who received prenatal diagnosis and diagnosed with increased NT thickness and absence of nasal bone were 17.6% (46/262) and 14.3% (29/203), respectively. ②The incidence of chromosomal abnormalities of fetus with isolated increased NT thickness, isolated absence of nasal bone, increased NT thickness + absence of nasal bone, increased NT thickness + other structure abnormalities, and increased NT thickness + absence of nasal bone + other structure abnormalities were 8.5% (17/200), 3.9% (3/77), 53.5% (23/43), 43.5% (10/23), 42.9% (6/14), respectively. Among them, there was no significant difference of incidence of chromosomal abnormalities between fetus with isolated increased NT thickness and isolated absence of nasal bone (χ²=1.759, P=0.090). There was no significant difference of incidence of chromosomal abnormalities among fetus with the rest of 3 ultrasound conditions (χ²=0.837, P=0.658). But the incidence of chromosomal abnormalities of fetus with these 3 ultrasound conditions were all higher than that of fetus with isolated increased NT thickness, and the differences were statistically significant(χ²=52.080, 23.716, 16.101; all P<0.001).

Nasal bone screening should be included as a screening index of chromosomal abnormality in first trimester, and fetus with nasal bone abnormality should be followed up in second trimester. It is highly recommended that pregnant women take prenatal diagnosis while ultrasound scan showed fetus with increased NT thickness combined with absence of nasal bone and/or with other structure abnormalities to identify fetus condition of occurrence of chromosomal abnormality.