分析早孕期双胎妊娠胎儿颈项透明层（NT）增厚与不良妊娠结局之间的关系。

选取于2017年5月至2020年8月间在南京医科大学附属苏州医院进行早孕期超声筛查的双胎妊娠孕妇503例。参照英国胎儿医学基金会的指南分别测量2个胎儿的头臀长及NT厚度并随访其妊娠结局，分为2个胎儿NT厚度均正常组及至少1个胎儿NT增厚组，比较2组双胎妊娠的妊娠结局；至少1个胎儿NT增厚组又分为双绒毛膜性双羊膜囊双胎（DCDA）亚组及单绒毛膜双羊膜囊双胎（MCDA）亚组，比较两亚组妊娠结局，至少1个胎儿NT增厚组又分为NT≥第95百分位数亚组及NT≥第99百分位数亚组，比较两亚组妊娠结局。采用χ²检验或Fisher精确概率法比较上述组间妊娠结局的差异。

503例双胎妊娠1006例胎儿NT厚度值为（1.83±0.56）mm（范围0.8~10.0 mm）。2个胎儿NT厚度均正常组455例（455/503，90.46%），其中出现不良妊娠结局者57例（57/455，12.52%）；至少1个胎儿NT增厚组48例（48/503，9.54%），其中出现不良妊娠结局者15例（15/48，31.25%）。至少有1个胎儿NT增厚的双胎妊娠不良妊娠结局发生率明显高于2个胎儿NT厚度均正常者，差异具有统计学意义（χ²=12.409，P＜0.001）。至少1个胎儿NT增厚时，发生流产或死胎者共4例（4/48，8.33%），2个胎儿NT厚度均正常者发生流产或死胎者共12例（12/455，2.64%），两者比较，差异具有统计学意义（χ²=4.574，P=0.032）。DCDA亚组37例（37/48，77.08%），其中出现不良妊娠结局者8例（8/37，21.62%）；MCDA亚组11例（11/48，22.92%），其中出现不良妊娠结局者7例（7/11，63.63%），MCDA亚组不良妊娠结局发生率明显高于DCDA亚组，差异具有统计学意义（χ²=6.967，P=0.008）。NT≥第95百分位数亚组35例，其中出现不良妊娠结局者10例（10/35，28.57%），NT≥第99百分位数亚组13例，其中出现不良妊娠结局者5例（5/13，38.46%），NT≥第95百分位数亚组发生不良妊娠结局与NT≥第99百分位数亚组比较，差异无统计学意义（χ²=0.432，P=0.511），NT≥第95百分位数亚组中出现终止妊娠结局1例（1/35，2.86%），NT≥第99百分位数亚组中出现终止妊娠结局4例（4/13，30.77%），NT≥第99百分位数亚组发生终止妊娠结局较NT≥第95百分位数亚组明显升高，差异具有统计学意义（χ²=7.914，P=0.005）。

NT厚度是早孕期超声筛查的重要软指标。在双胎妊娠中，尤其是在MCDA双胎中，早孕期超声筛查发现NT增厚，对胎儿发生不良妊娠结局有一定的提示作用。

To analyze the relationship between nuchal translucency (NT) thickening and adverse pregnancy outcomes in twins during the first trimester.

Five hundred and three twin pregnancies were selected from those who underwent first trimester ultrasound screening during May 2017 to August 2019 at the Affiliated Suzhou Hospital of Nanjing Medical University, including 367 cases of dichorionic diamniotic (DCDA) twin pregnancy, 132 cases of monochoric diamniotic (MCDA) twin pregnancy, and 4 cases of monochoric monoamniotic (MCMA) twin pregnancy. The fetal crown-rump length (CRL) and NT thickness were measured according to the guidelines of the Fetal Medicine Foundation (FMF) and the pregnancy outcomes were followed. The pregnancy outcomes of twin pregnancy were compared between the group with normal fetal NT thickness in both fetuses and the group with NT thickening in at least one fetus. The latter group was further divided into a DCDA subgroup and an MCDA subgroup, and the former group was further divided into an NT ≥ 95th percentile subgroup and an NT ≥ 99th percentile subgroup. Differences in pregnancy outcomes between the above groups or subgroups were compared using the χ² test or Fisher exact probability method.

The average NT thickness of 1006 fetuses from 503 twin pregnancies was (1.83±0.56) mm (range, 0.8~10.0 mm). Four hundred and fifty-five cases (455/503, 90.46%) had normal fetal NT thickness in both fetuses, of which 57 (57/455, 12.52%) had abnormal pregnancy outcomes. Forty-eight cases (48/503, 9.54%) had NT thickening in at least one fetus, of which 15 (15/48, 31.25%) had abnormal pregnancy outcomes. The incidence of adverse pregnancy outcomes in twin pregnancy with NT thickening in at least one fetus was significantly higher than that with normal NT thickness in both fetuses (χ²=12.409, P＜0.001). There were 4 cases (4/48, 8.33%) of abortion or stillbirth when NT was thickened in at least one fetus, and 12 cases (12/455, 2.64%) of abortion or stillbirth occurred when the NT thickness of both fetuses was normal; the difference was statistically significant (χ²=4.574, P=0.032). There were 37 (37/48, 77.08%) cases in the DCDA subgroup, of which 8 (8/37, 21.62%) had adverse pregnancy outcomes. There were 11 (11/48, 22.92%) cases in the MCDA subgroup, of which 7 (7/11, 63.63%) had adverse pregnancy outcomes. The difference in the cases with adverse pregnancy outcomes was statistically significant between the two subgroups (χ²=6.967, P=0.008). There were 35 cases in the NT≥95th percentile subgroup, of which 10 (10/35, 28.57%) had adverse pregnancy outcomes, and 13 cases in the NT≥99th percentile subgroup, of which 5 (5/13, 38.46%) had adverse pregnancy outcomes; there was no significant difference in cases with adverse pregnancy outcomes between the two subgroups (χ²=0.432,P=0.511). One (1/35, 2.86%) case of termination of pregnancy occurred in the NT≥95th percentile subgroup, but there were 4 (4/13, 30.77%) cases in the NT≥99th percentile subgroup; there was a significant difference between the two groups (χ²=7.914,P=0.005).

NT thickness is an important ultrasonic soft marker during the first trimester. In twin pregnancy, especially in MCDA, NT thickening during the first trimester screening may indicate adverse pregnancy outcomes.