Department of Biological Psychology, VU University, The Netherlands.
BMC Pediatr. 2011 Apr 1;11:24. doi: 10.1186/1471-2431-11-24.
Triplets are often born premature and with a low birth weight. Because the incidence of triplet births is rare, there are relatively few studies describing triplet birth weight characteristics. Earlier studies are often characterized by small sample sizes and lack information on important background variables such as zygosity. The objective of this study is to examine factors associated with birth weight in a large, population-based sample of triplets registered with the Netherlands Twin Register (NTR).
In a sample of 1230 triplets from 410 families, the effects of assisted reproductive techniques, zygosity, birth order, gestational age, sex, maternal smoking and alcohol consumption during pregnancy on birth weight were assessed. The resemblance among triplets for birth weight was estimated as a function of zygosity. Birth weight discordance within families was studied by the pair-wise difference between triplets, expressed as a percentage of the birth weight of the heaviest child. We compare data from triplets registered with the NTR with data from population records, which include live births, stillbirths and children that have deceased within days after birth.
There was no effect of assisted reproductive techniques on triplet birth weight. At gestational age 24 to 40 weeks triplets gained on average 130 grams per week; boys weighed 110 grams more than girls and triplets of smoking mothers weighted 104 grams less than children of non-smoking mothers. Monozygotic triplets had lower birth weights than di- and trizygotic triplets and birth weight discordance was smaller in monozygotic triplets than in di- and trizygotic triplets. The correlation in birth weight among monozygotic and dizygotic triplets was 0.42 and 0.32, respectively. In nearly two-thirds of the families, the heaviest and the lightest triplet had a birth weight discordance over 15%. The NTR sample is representative for the Dutch triplet population that is still alive 28 days after birth.
Birth weight is an important determinant of childhood development. Triplet status, gestational age, sex, zygosity and maternal smoking affect birth weight. The combined effects amount to a difference of 364 grams between monozygotic girl triplets of smoking mothers compared to dizygotic boy triplets of non-smoking mothers of the same gestational age. Birth weight in triplets is also influenced by genetic factors, as indicated by a larger correlation in monozygotic than in di- and trizygotic triplets.
三胞胎通常早产且出生体重低。由于三胞胎的出生率较低，描述三胞胎出生体重特征的研究相对较少。早期的研究通常存在样本量小且缺乏重要背景变量（如合子性）信息的问题。本研究的目的是在荷兰双胞胎登记处（NTR）登记的三胞胎的大型人群样本中，研究与出生体重相关的因素。
在来自 410 个家庭的 1230 例三胞胎样本中，评估了辅助生殖技术、合子性、出生顺序、胎龄、性别、母亲在怀孕期间吸烟和饮酒对出生体重的影响。根据合子性来评估三胞胎之间出生体重的相似性。通过三胞胎之间的两两差异（以最重孩子的出生体重的百分比表示）来研究家庭内的出生体重差异。我们将 NTR 登记的三胞胎数据与包括活产、死产和出生后几天内死亡的人群记录数据进行比较。
辅助生殖技术对三胞胎的出生体重没有影响。在 24 至 40 周的胎龄时，三胞胎每周平均增加 130 克；男孩比女孩重 110 克，母亲吸烟的三胞胎比不吸烟母亲的孩子轻 104 克。同卵三胞胎的出生体重低于异卵和三卵三胞胎，同卵三胞胎的出生体重差异小于异卵和三卵三胞胎。同卵和异卵三胞胎之间出生体重的相关性分别为 0.42 和 0.32。在近三分之二的家庭中，最重和最轻的三胞胎之间的出生体重差异超过 15%。NTR 样本代表了荷兰出生后 28 天仍存活的三胞胎人群。
出生体重是儿童发育的一个重要决定因素。三胞胎状态、胎龄、性别、合子性和母亲吸烟都会影响出生体重。综合影响因素导致同卵性别的吸烟母亲所生的女孩三胞胎与同胎龄非吸烟母亲所生的异卵性别的男孩三胞胎之间的出生体重相差 364 克。三胞胎的出生体重还受到遗传因素的影响，同卵三胞胎之间的相关性大于异卵和三卵三胞胎。
