Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Sunnybrook Health Sciences Centre, University of Toronto, Ontario, Canada.
Department of Anatomic Pathology, Sunnybrook Health Sciences Centre, University of Toronto, Ontario, Canada.
Placenta. 2017 Dec;60:28-35. doi: 10.1016/j.placenta.2017.10.002. Epub 2017 Oct 13.
Twin fetuses grow slower during the third trimester compared with singletons. However, the extent to which the relative smallness of twins is the result of placenta-mediated factors similar to those associated with fetal growth restriction in singletons remains unclear. Our aim was to address this question by comparing placental findings between small for gestational age (SGA) twins and SGA singletons.
Retrospective cohort study of all SGA non-anomalous newborns from singleton and dichorionic twin pregnancies in a single tertiary referral center between 2002 and 2015. SGA was defined as birth weight <10th percentile for gestational age according to sex-specific national reference charts. Placental findings were compared between SGA twins and SGA singletons and were classified into lesions associated with maternal vascular malperfusion, fetal vascular malperfusion, placental hemorrhage and chronic villitis.
A total of 532 SGA twins and 954 SGA singletons met the inclusion criteria. SGA twins had a higher mean placental weight (371 ± 103 g vs. 319 ± 107, p < 0.001) and a lower fetal-placental ratio (6.0 ± 2.5 vs. 6.7 ± 3.2, p < 0.001) compared with SGA singletons. Compared with SGA singletons, SGA twins were less likely to have any placental pathology (aOR 0.37, 95%-CI 0.29-0.46), hypercoiled cord (aOR 0.45, 95%-CI 0.33-0.61), placental weight<10th% (aOR 0.13, 95%-CI 0.08-0.20), maternal vascular malperfusion pathology (aOR 0.24, 95%-CI 0.18-0.30) and fetal vascular malperfusion pathology (aOR 0.62, 95%-CI 0.48-0.82). By contrast, SGA twins had higher odds of a marginal or velamentous cord insertion compared with SGA singletons (aOR 13.82, 95%-CI 10.44-18.30). Similar significant associations were observed in subgroups of SGA fetuses with a birth weight below the 5th and 3rd percentile for gestational age.
Our findings illustrate that the mechanisms underlying reduced fetal growth in dichorionic twins differ from those involved in singletons, and may provide support to the hypothesis that smallness in dichorionic twins may be more benign than in singletons.
与单胎妊娠相比，双胎妊娠在妊娠晚期胎儿生长速度较慢。然而，双胞胎的相对较小程度是由胎盘介导的因素引起的，这些因素类似于单胎胎儿生长受限相关的因素，这一点仍不清楚。我们的目的是通过比较小胎龄儿（SGA）双胎妊娠和 SGA 单胎妊娠的胎盘发现来解决这个问题。
这是一项在 2002 年至 2015 年期间在一家三级转诊中心进行的所有 SGA 非畸形新生儿的单胎和双绒毛膜双胞胎妊娠的回顾性队列研究。SGA 定义为根据性别特异性国家参考图表，出生体重低于胎龄第 10 百分位。比较 SGA 双胞胎和 SGA 单胎妊娠的胎盘发现，并将其分类为与母体血管灌注不良、胎儿血管灌注不良、胎盘出血和慢性绒毛膜炎相关的病变。
共有 532 例 SGA 双胞胎和 954 例 SGA 单胎妊娠符合纳入标准。与 SGA 单胎妊娠相比，SGA 双胞胎的胎盘重量（371±103g 比 319±107g，p<0.001）更高，胎儿胎盘比值（6.0±2.5 比 6.7±3.2，p<0.001）更低。与 SGA 单胎妊娠相比，SGA 双胞胎更不可能有任何胎盘病理（aOR 0.37，95%CI 0.29-0.46）、脐带过度卷曲（aOR 0.45，95%CI 0.33-0.61）、胎盘重量<10%（aOR 0.13，95%CI 0.08-0.20）、母体血管灌注不良病理（aOR 0.24，95%CI 0.18-0.30）和胎儿血管灌注不良病理（aOR 0.62，95%CI 0.48-0.82）。相比之下，SGA 双胞胎的边缘或帆状脐带插入的可能性高于 SGA 单胎妊娠（aOR 13.82，95%CI 10.44-18.30）。在出生体重低于胎龄第 5 百分位和第 3 百分位的 SGA 胎儿亚组中，也观察到了类似的显著关联。
我们的研究结果表明，双绒毛膜双胞胎中胎儿生长受限的机制与单胎妊娠中涉及的机制不同，这可能支持这样一种假设，即双绒毛膜双胞胎的大小可能比单胎妊娠更良性。
