双胎及出生体质量不同一性双胎胎儿宫内生长发育的特点

Intrauterine growth characteristics of twins and those twins discordant birthweight

目的探讨双胎及出生体质量不同一性双胎（不同一性双胎）胎儿宫内生长发育的特点。方法选择2000年1月至2010年7月在中山大学附属第一医院及2000年1月至2009年12月在附属第三医院住院分娩，有完整临床资料的双胎孕妇1010例及其2020个胎儿，以双胎胎儿间出生体质量差异≥25％为不同一性双胎的标准诊断，不同一性双胎孕妇共119例及其238个胎儿为不同一性双胎组；双胎间出生体质量差异〈25％的891例孕妇及其1782个胎儿为出生体质量同一性双胎（同一性双胎组）。随机选择同期分娩的单胎孕妇4042例及其4042个胎儿作为单胎对照组。结果（1）两组双胎的临床资料比较：不同一性双胎组的大胎出生体质量、小胎出生体质量及双胎胎儿间出生体质量差异分别为（2090±827）g、（1392±592）g及（33．9±9．3）％，同一性双胎组分别为（2408±543）g、（2191±505）g及（8．9±6．5）％，两组各项分别比较，差异均有统计学意义（P〈0．01）。不同一性双胎发生率为11．78％（119／1010）。与同一性双胎组相比，不同一性双胎组晚期流产率、单绒毛膜双胎所占比例较高（P〈0．05），其脐带附着异常、双胎输血综合征和妊娠期高血压疾病的发生率均明显高于同一性双胎组（P〈0．05）。（2）双胎胎儿出生体质量的分布特点：①双胎妊娠的2020个胎儿中，80．05％（1617／2020）的双胎胎儿出生体质量小于单胎对照组同孕周胎儿的第50百分位数，而23．71％（479／2020）的双胎胎儿出生体质量小于单胎对照组同孕周胎儿的第10百分位数。②从孕19周开始，总体双胎胎儿出生体质量的第50、90百分位数均低于单胎对照组同孕周胎儿出生体质量的相应百分位数；孕38周之后，单胎对照组胎儿出生体质量仍继续增长，并在孕41周时达到出生体质量中位数的最大值；而双胎胎儿出生体质量中位数在孕38周时即达峰值，孕39周后出现下降趋势，并低于单胎对照组胎儿的第10百分位数。③不同一性双胎组中大胎与小胎的出生体质量的分布特点：65例（54．6％，65／119）大胎和1例（0．8％，1／119）小胎的出生体质量高于总体双胎胎儿出生体质量的第50百分位数；而5例（4．2％，5／119）大胎和97例（81．5％，97／119）小胎的出生体质量低于总体双胎胎儿出生体质量的第10百分位数。结论（1）双胎胎儿的出生体质量随孕周变化及增长趋势与单胎不同，评估双胎胎儿宫内生长发育情况应采用双胎胎儿的出生体质量标准。（2）若以双胎胎儿出生体质量作为参考标准，多数的不同一性双胎中至少一胎存在宫内生长受限的情况。

Objective To investigate the intrauterine growth characteristics of twins and birthweight discordant twins （discordant twins）. Methods Total of 1010 twin pregnancies （2020 fetuses） with complete delivery records from the Department of Obstetrics and Gynecology, the First and Third Affiliated Hospital of SUN Yat-sen University between January 1, 2000 and July 31, 2010 were studied retrospectively. One handred and ninteen cases （238 fetuses） with intrapair birthweight difference ≥ 25% were determined as the discordant twins group, and the other 891 eases （1782 fetuses） with intrapair birthweight difference 〈 25% were identified as the concordant twins group. The singleton control group included 4042 singleton pregnancies in the same period. Results （ 1 ） Comparison of clinical data between the twins groups： the birthweight of larger-twin, smaller-twin and intrapair birthweight difference in the discordant twins group and the concordant twins group were （2090 ± 827） g, （1392 ± 592） g, （33.9 ± 9. 3）%, and （2408±543） g, （2191 ±505） g, （8.9 ±6. 5）%, respectively, with significant differences （P 〈 0. 01 ）. The incidence of discordant twins was 11.78% （ 119/1010）. Compared with the concordant twins group, the discordant twins group had higher proportion of monoehorionic twins, and higher prevalence of pregnancy complications such as late miscarriage, abnormal umbilical insertion, twin-twin transfusion syndrome and hypertensive disorders in pregnancy （ P 〈 0. 05 ）. （ 2 ） The characteristics of twin birthweight distribution：（1） In all the 2020 twins, 80. 05% （1617/2020） fetuses had birthweight below the 50^th percentile of the singleton control group, while 23.71% （479/2020） feeuses got birthweight below the 10^th percentile of the singleton control group. （2） After 19^th gestational week, the 50^th and 90^th percentile of all twins＇ birthweight were lower than those of singletons. After 38^th gestational week, the birthweight of singletons kept increasing and reached its peak at 41^th week, while the birthweight of twins reached its peak at 38^th week, followed by a decline at 39 weeks, which was even lower than the 10^th percentile of the singleton control group. （3） The distribution of birthweight of larger- and smaller-twin in the discordant twins group ：65 （54. 6% , 65/119） larger-twins and one （0. 8% , 1/119） smaller-twin had birthweight above the 50^th percentile of all twins, while 5 （4. 2%, 5/119） larger-twins and 97 （81.5%, 97/119） smaller-twins got birthweight below the 10^th percentile of all twins. Conclusions （ 1 ） The patterns of birthweight curves for each gestational week are different between twins and singletons. In order to evaluate the growth of twins, birthweight reference for twins should be employed. （2） According to the reference of twins birthweight, the most discordant twins are complicated with fetal growth restriction at least in one twin.