Davies Michael J
Research Centre for Reproductive Health, Department of Obstetrics and Gynaecology, University of Adelaide, Australia.
Reprod Fertil Dev. 2005;17(3):379-86. doi: 10.1071/rd04101.
Multiple pregnancy is associated with increased risk of adverse consequences for both mother and fetus(es), including increased rates of maternal hypertension and pre-eclampsia, spontaneous abortion, Caesarean delivery, low birthweight, birth prematurity, perinatal mortality, admission to neonatal intensive care and extended length of care, respiratory distress, cerebral palsy, developmental delay, contact with disability services and mortality to age 5 years. Premature birth, which affects 97% of triplets and 53.3% of twins in Australia, is not the sole factor involved. The rate of multiple pregnancy in Australia is 1.7%. This compares to 22.1% for pregnancies resulting from assisted reproduction technology (ART). As a result, 21.8% of babies born from ART are from a multiple pregnancy, in comparison to the USA where the majority of babies born from ART are from a multiple pregnancy. Additionally, the population rate of multiple births is rising due to the more frequent use of ART and continued multi-embryo transfers, which is operating against a background of rising implantation rates within ART clinics. Twins have been of interest from a programming perspective. However, analysis of associations between crude birthweight and subsequent metabolic risk factors or mortality in adulthood from chronic disease indicate that adaptations in pregnancy to support multi-fetal growth are not identical to fetal growth restriction in singleton pregnancies. Indeed, the process of 'maternal constraint' is incompletely understood and confounds such comparisons. From a programming perspective, it is a challenge to identify in twin pregnancies the transition from physiological adaptation to pathological growth restriction. Growth disparity between twins has been more illuminating of subtle adverse effects for the smaller of twin pairs in both blood pressure and insulin resistance in adulthood. Interestingly, these effects can be observed in both dizygotic and to a lesser degree in monozygotic twins, which indicates a role for both genetic and environmental factors in these measures. This suggests that, consistent with experimental studies in other species, the relationship between impaired growth in utero and chronic disease in later life is not simply mediated by a common genetic pathway.
多胎妊娠与母亲和胎儿出现不良后果的风险增加相关，包括母亲高血压和先兆子痫、自然流产、剖宫产、低出生体重、早产、围产期死亡率、入住新生儿重症监护病房以及护理时间延长、呼吸窘迫、脑瘫、发育迟缓、与残疾服务机构接触以及5岁前死亡率增加。早产影响了澳大利亚97%的三胞胎和53.3%的双胞胎，但它并非唯一涉及的因素。澳大利亚的多胎妊娠率为1.7%。相比之下，辅助生殖技术（ART）导致的妊娠率为22.1%。因此，ART出生的婴儿中有21.8%来自多胎妊娠，而在美国，ART出生的大多数婴儿来自多胎妊娠。此外，由于ART的使用更加频繁以及持续进行多胚胎移植，多胞胎的人口比率正在上升，这一情况是在ART诊所着床率上升的背景下发生的。从编程的角度来看，双胞胎一直备受关注。然而，对出生体重与成年后慢性疾病的后续代谢风险因素或死亡率之间关联的分析表明，孕期为支持多胎生长而进行的适应性变化与单胎妊娠中的胎儿生长受限并不相同。事实上，“母体限制”过程尚未完全被理解，这使得此类比较变得复杂。从编程的角度来看，在双胎妊娠中识别从生理适应到病理性生长受限的转变是一项挑战。双胞胎之间的生长差异更能说明较小的双胞胎在成年期血压和胰岛素抵抗方面存在的细微不良影响。有趣的是，这些影响在异卵双胞胎中均可观察到，在同卵双胞胎中程度稍轻，这表明遗传和环境因素在这些指标中都发挥了作用。这表明，与其他物种的实验研究一致，子宫内生长受损与晚年慢性疾病之间的关系并非简单地由共同的遗传途径介导。
