探讨双胎消失综合征(VTS)存活儿围生期结局及其危险因素。

选择2020年1月1日至12月31日，北京市妇幼保健网络信息系统"北京市围生保健管理登记卡"中登记的155 560例单胎分娩儿为研究对象。采用回顾性研究方法，根据孕母是否为双胎妊娠，将VTS存活儿纳入研究组(n＝381)，单胎妊娠儿(以下简称为单胎儿)纳入对照组(n＝155 179)。根据孕母受孕方式，将研究组与对照组胎儿进一步分为N研究亚组(n＝187，自然受孕胎儿)与A研究亚组[n＝194，采取辅助生殖技术(ART)受孕胎儿]，以及N对照亚组(n＝149 900，自然受孕胎儿)与A对照亚组(n＝5 279，采取ART受孕胎儿)。采用成组t检验、χ²检验、连续性校正χ²检验、Fisher确切概率法，对研究组与对照组及其不同亚组新生儿早产、低出生体重儿、足月小于胎龄儿、围生期死亡、出生缺陷等，研究组与对照组新生儿孕母临床资料进行统计学比较。采用多因素非条件logistic回归分析，对单胎分娩儿围生期结局影响因素进行分析。研究组与对照组新生儿性别构成比等一般临床资料比较，差异无统计学意义(P>0.05)。本研究遵循的程序符合首都医科大学附属北京妇产医院/北京妇幼保健院医学伦理委员会规定，通过该伦理委员会批准(审批文号：2018-KY-039-01)。

①研究组、N研究亚组、A研究亚组新生儿出生胎龄<34周、<37周及出生体重<2 500 g、足月小于胎龄儿与出生缺陷发生率，均分别显著高于对照组、N对照亚组、A对照亚组新生儿，并且差异均有统计学意义(P<0.05)。研究组与对照组、N研究亚组与N对照亚组、A研究亚组与A对照亚组新生儿围生期死亡率分别比较，差异均无统计学意义(P>0.05)。②研究组新生儿孕母高龄(分娩年龄≥35岁)、首次妊娠、初产妇、ART受孕、不良孕产史、子宫异常史、孕前3个月至早孕期规律服用叶酸、三级助产技术服务机构分娩、妊娠期高血压疾病、剖宫产术分娩比例，均显著高于对照组，并且差异均有统计学意义(P<0.001)。③多因素非条件logistic回归分析结果显示，VTS存活儿发生出生缺陷、早产、低出生体重和足月小于胎龄儿的风险分别是单胎儿的2.291倍(OR＝2.291，95%CI：1.643~3.196，P<0.001)，2.572倍(OR＝2.572，95%CI：1.939~3.413，P<0.001)，3.577倍(OR＝3.577，95%CI：2.654~4.821，P<0.001)和4.178倍(OR＝4.178，95%CI：2.445~7.140，P<0.001)，但是围生期死亡风险与单胎儿比较，增加不显著(OR＝1.589，95%CI：0.386~6.536，P＝0.521)。

本研究VTS存活儿与单胎儿的围生期死亡率基本相当，但是VTS存活儿早产、低出生体重、足月小于胎龄儿、出生缺陷风险及孕母发生妊娠期高血压疾病风险较单胎儿增高。早孕期超声发现VTS，并加强产前检查和胎儿畸形筛查，对于改善其母婴围生期结局具有积极意义。

To explore perinatal outcomes of surviving baby after vanishing twin syndrome (VTS) and its risk factors.

A total of 155 560 babies of single delivered in Beijing from January 1, to December 31, 2020 were selected as research subjects. The pregnant mothers underwent early pregnancy ultrasound examinations and their pregnancy outcomes were registered in the Beijing Maternal and Child Health Information Network System. Surviving babies after VTS (hereinafter referred to as survivors) were included into study group (n=381), and those singletons pregnancy (hereinafter referred to as singletons) were included into control group (n=155 179), according to whether mother was twin pregnancy or not by retrospective study method. According to fertilization method, babies in study group and control group were further divided into N study subgroup (n=187, natural fertilization) and A study subgroup [n=194, by assisted reproductive technology (ART)], N control subgroup (n=149 900, natural fertilization) and A control subgroup (n=5 279, by ART). Independent-samples t test, chi-square test, continuity-corrected chi-square test and Fisher probabilities test were used for statistical comparison of babies between study group and control group and their subgroups about incidences of preterm birth, low birth weight, full-term small for gestational age infant, perinatal death, birth defects and other perinatal outcomes, and clinical data of their pregnant mothers. Multivariate unconditional logistic regression analysis was used to analyze the influencing factors of perinatal outcomes of all babies. There were no significant differences in general clinical data such as gender composition between study group and control group (P>0.05). The procedures followed in this study complied with the regulations of the Medical Ethics Committee of Beijing Obstetrics and Gynecology Hospital, Capital Medical University/Beijing Maternal and Child Health Hospital, and were approved by the ethics committee (Approval No. 2018-KY-039-01).

①The incidences of preterm birth <34 weeks, preterm birth <37 weeks, low birth weight (<2 500 g), full-term small for gestational age infant and birth defects in study group, A study subgroup, B study subgroup all were significantly higher than those in control group, A control subgroup, B control subgroup, respectively, and all differences were statistically significant (P<0.05). There were no significant differences of babies between study group and control group and their subgroups in perinatal mortality (P>0.05). ②The rate of pregnant mothers ≥35-year old, first pregnancy, primipara, ART conception, adverse pregnancy history, uterine abnormalities, regular use of folic acid from 3 months before pregnancy to the first trimester, delivery in a grade-A tertiary midwifery institution, hypertension in pregnancy and cesarean section delivery in study group were significantly higher than those in control group, and all differences were statistically significant (P<0.001). ③Multivariate unconditional logistic regression analysis showed that the risks of birth defects, preterm birth <37 weeks, low birth weight and full-term small for gestational age in survivors were 2.291 times (OR=2.291, 95%CI: 1.643-3.196, P<0.001), 2.572 times (OR=2.572, 95%CI: 1.939-3.413, P<0.001), 3.577 times (OR=3.577, 95%CI: 2.654-4.821, P<0.001) and 4.178 times (OR=4.178, 95%CI: 2.445-7.140, P<0.001) of singletons respectively. The perinatal mortality of survivors was increased non-significantly compared with singletons (OR=1.589, 95%CI: 0.386-6.536, P=0.521).

Perinatal mortality of survivors after VTS in twin pregnancies conceived naturally or by ART is not significantly different from singletons. But the risks of preterm birth, low birth weight, full-term small for gestational age infant, birth defects of survivors after VTS and the risk of hypertension in pregnancy of their pregnant mothers are increased compared with singletons. Early detection for VTS by ultrasound, regular prenatal examinations and fetal malformation screening could improve the perinatal outcomes.