双胎出生体重的影响因素及不同一性双胎的高危因素分析

Antenatal factors associated with birth weight of twins and risk factors for discordant twins

目的探讨双胎出生体重的影响因素及发生不同一性双胎的高危因素。方法收集2000年1月至2009年12月在中山大学附属第三医院及2000年1月至2009年6月在中山大学附属第一医院住院分娩的834例双胎妊娠的临床资料，以双胎问出生体重差异≥25％为标准诊断不同一性双胎75例，采用协方差分析及非条件Logistic回归方法回顾性分析多种因素与双胎出生体重及不同一性双胎的关系。结果本组资料不同一性双胎的发生率为8．99％（75／834）。孕妇年龄、受孕方式、绒毛膜性质、妊娠期糖尿病、脐带附着情况均与双胎出生体重存在相关性（相应的P值分别为0．021、0．000、0．000、0．012、0．017），而妊娠期高血压疾病、产次以及胎儿是否为同性别与双胎出生体重无相关性（P〉O．05）。非条件Logistic回归分析显示，妊娠期高血压疾病和单绒毛膜性质是不同一性双胎的高危因素，其OR值（95％CI）分别为2．600（1．566～4．316）、1．833（1．010～3．582）。将孕妇年龄分为4个阶段，即〈25岁组（69例）、～30岁组（312例）、～35岁组（325例）、高龄组（≥35岁）（128例），各组双胎的平均出生体重分别为：（2205±483）g、（2347±406）g、（2381±439）g和（2352±455）g，除～35岁组与高龄组比较，双胎平均出生体重差异无统计学意义外（P〉0．05），其他各组两两比较，差异均有统计学意义（P〈0．05）。将新生儿性别分类后发现：不同性别双胎中男胎（270例）的平均出生体重为（2416±514）g，同性别男胎292例，平均出生体重（2381±428）g，不同性别双胎中女胎270例，同性别女胎272例，平均出生体重分别为（2322±488）g和（2301±418）g。除了不同性别双胎中男胎的出生体重与同性别男胎的体重比较，差异无统计学意义（P〉0．05）外，其他各组两两比较，差异均有统计学意义（P〈0．05）。结论双胎妊娠如孕妇年龄小于25岁、单绒毛膜性质、脐带边缘或帆状附着或女性双胎，则双胎胎儿的出牛体重明显下降；如为辅助生殖技术后妊娠或合并妊娠期糖尿病，则取胎胎儿的出生体重增加。双胎妊娠合并妊娠期高血压疾病或单绒毛膜性质时。应警惕双胎不同一性的发生。

Objective To investigate the antenatal influencing factors associated with birth weight of twins and the risk factors for the occurrence of discordant twins. Methods Totally, 834 twins delivered at the Third Affiliated Hospital from January 2000 to December 2009 and the First Affiliated Hospital of SUN Yat sen University, from January 2000 to June 2009, were recruited in the study. The diagnosis criteria of discordant twins was intrapair birth weight difference more than 25%. Antenatal factors on birth weight were retrospectively investigated among twins and discordant twins respectively with Logistic analysis. Results （1） There were several factors associated with birth weight of twins, including maternal age, conceptive style, chorionicity, gestational diabetes mellitus and placental cord insertion （P = 0. 021, 0. 000, 0. 000, 0. 012 and 0. 017, respectively）. While hypertensive disorder in pregnancy, parity and fetal gender differences were not associated with the birth weight of twins （P〉0.05）. Hypertensive disorder in pregnancy （OR =2.600, 95% CI：1. 566 4. 316） and monochorionicity （OR=1.833, 95% CI：1.010-3.582） were risk factors of discordant twins. All 834 twin pregnancies were divided into 4 groups according to rnateral age, 〈25 yrs （n =69）, 25-30 yrs （n= 312）, 30-35 yrs （n=325） and ≥35 yrs （n=128）. The average birth weight of twins were （2205±483） g, （2347±406） g, （2381±439） g and （2352±455） g. Significant difference was found bewteen every two groups （P〈0.05） except that between the 30-35 yrs and ≥35 yrs group （P〉0.05）. Among twins of different gender （n=270）, the average birth weight of boys and girls were （2416±514） g and （2322±488） g, and that of female twins （n=272） and male twins （n 292） were （2301±418） g and （2381±428） g. Significant difference was shown between every two groups （P〈0.05） except that between the male twins and male fetus of twins of different gender （P〉0.05）. Conclusions The fetal birth weight of twins decreases remarkably when maternal age 〈 25, or monochorionicity twins, or complicated with marginal or velamentous placental cord insertion or female pairs. However, birth weight of twins would increase if the pregnancy conceived by assisted reproductive technology or complicated with gestational diabetes mellitus. Twin pregnancy complicated with hypertensive disorder in pregnancy or monoehorionicity should alert the clinicians of discordance twins.