Background

Serial growth scans are routinely recommended for twin pregnancies to identify fetal growth restriction (defined as an estimated fetal weight of <10th percentile), which can result in increased perinatal morbidity and mortality. However, the clinical significance of early intertwin growth discordance in the absence of fetal growth restriction remains unclear.

Objective

This study aimed to compare the rates of small-for-gestational-age infants among twin pregnancies with intertwin growth discordance in the absence of fetal growth restriction with that among twin pregnancies with concordant, normal growth identified by ultrasound between 24 0/7 and 31 6/7 weeks’ gestation.

Study Design

This was a retrospective cohort study of twin deliveries at a single hospital from 2010 to 2019. Pregnancies without fetal growth restriction were categorized as discordant or concordant using the earliest prenatal growth ultrasound between 24 0/7 and 31 6/7 weeks’ gestation. Discordance was defined as an estimated fetal weight difference of ≥18% between twins. Pregnancies with major fetal anomalies, no growth ultrasound between 24 0/7 and 31 6/7 weeks’ gestation, or twin-twin transfusion syndrome were excluded. The cohort was stratified by chorionicity. Our primary outcome was small-for-gestational-age defined as <10th percentile per the Fenton growth curve at delivery. Secondary outcomes included gestational age at delivery, mode of delivery, neonatal intensive care unit admission, length of stay, and neonatal complications and placental pathology.

Results

Of the 707 twin pregnancies that met the inclusion criteria, 558 (79%) were dichorionic and 149 (21%) were monochorionic. Most pregnancies were concordant on ultrasound between 24 0/7 and 31 6/7 weeks’ gestation (dichorionic, 93%; monochorionic, 87%). Regardless of chorionicity, twin pregnancies with discordance at ultrasound, were more likely to have a small-for-gestational-age infant than concordant twin pregnancies (dichorionic: 51% vs 29%; P=.002; monochorionic: 65% vs 24%; P<.001). Furthermore, women with twin pregnancies with discordance were delivered at an earlier gestational age (dichorionic: 36 weeks [interquartile range, 33–36] vs 34 weeks [interquartile range, 34–38]; P<.001; monochorionic: 34 weeks [interquartile range, 32–34] vs 36 weeks [interquartile range, 34–37]; P=.003). Pregnancies with growth discordance were more likely to be delivered by cesarean delivery (dichorionic: 90% vs 72%; P=.01; monochorionic: 65% vs 60%; P=.70), although this was only statistically significant for dichorionic twin pregnancies. Neonates of pregnancies with growth discordance had a higher incidence of respiratory distress syndrome (dichorionic: 54% vs 37%; P=.04; monochorionic: 70% vs 45%; P=.04) and neonatal intensive care unit admission (dichorionic: 71% vs 50%; P=.01; monochorionic: 90% vs 65%; P=.03). Furthermore, dichorionic infants had longer neonatal intensive care unit stays (30 [interquartile range, 18–61] vs 18 [interquartile range, 10–35] days; P=.02).

Conclusion

Regardless of chorionicity, twin pregnancies with discordance without fetal growth restriction identified on growth ultrasound between 24 0/7 and 31 6/7 weeks’ gestation were nearly twice as likely to develop small-for-gestational-age neonates, deliver earlier in gestation, and experience greater neonatal morbidity than twin pregnancies without discordance. Patients with pregnancies complicated by isolated intertwin discordance between 24 0/7 and 31 6/7 weeks’ gestation will need counseling regarding adverse perinatal outcomes.

中文翻译：

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双绒毛膜和单绒毛膜双胎妊娠早期双胎生长不一致后小于胎龄儿出生体重的发生率

背景

通常建议对双胎妊娠进行系列生长扫描，以识别胎儿生长受限（定义为估计胎儿体重<第 10 个百分位），这可能导致围产期发病率和死亡率增加。然而，在没有胎儿生长限制的情况下，早期双胞胎生长不一致的临床意义仍不清楚。

客观的

本研究旨在比较在没有胎儿生长限制的情况下，双胎妊娠中双胎间生长不一致的小于胎龄儿的比率，与在 24 0/7 至 31 之间通过超声确定生长一致、正常的双胎妊娠中的小于胎龄儿的发生率。怀孕6/7周。

学习规划

这是一项对 2010 年至 2019 年在同一家医院进行的双胞胎分娩的回顾性队列研究。使用妊娠 24 0/7 至 31 6/7 周之间最早的产前生长超声检查，将没有胎儿生长受限的妊娠分为不一致或一致。不一致的定义是双胞胎之间估计胎儿体重差异≥18%。排除有严重胎儿异常、妊娠 24 0/7 至 31 6/7 周期间未进行生长超声检查或双胎输血综合征的妊娠。该队列按绒毛膜性进行分层。我们的主要结局是小于胎龄，定义为分娩时芬顿生长曲线<第 10 个百分位数。次要结局包括分娩胎龄、分娩方式、新生儿重症监护病房入住、住院时间、新生儿并发症和胎盘病理学。

结果

在符合纳入标准的 707 例双胎妊娠中，558 例（79%）为双绒毛膜妊娠，149 例（21%）为单绒毛膜妊娠。大多数妊娠在妊娠 24 0/7 至 31 6/7 周之间超声结果一致（双绒毛膜，93%；单绒毛膜，87%）。无论绒毛膜性如何，超声检查不一致的双胎妊娠比一致的双胎妊娠更有可能生出小于胎龄儿的婴儿（双绒毛膜：51% vs 29%；P =.002；单绒毛膜：65% vs 24 %） ；P <.001)。此外，双胎妊娠不一致的女性在较早胎龄时分娩（双绒毛膜：36周[四分位范围，33-36] vs 34周[四分位范围，34-38]；P <.001；单绒毛膜：34周[四分位距，32–34] 与 36 周[四分位距，34–37]；P =.003）。生长不一致的妊娠更有可能通过剖腹产分娩（双绒毛膜：90% vs 72%；P =.01；单绒毛膜：65% vs 60%；P =.70），尽管这仅对双绒毛膜双胞胎具有统计学意义怀孕。生长不一致的妊娠新生儿呼吸窘迫综合征的发生率较高（双绒毛膜：54% vs 37%；P =.04；单绒毛膜：70% vs 45%；P =.04）和新生儿重症监护室入住率较高（双绒毛膜： 71% vs 50%；P =.01；单绒毛膜：90% vs 65%；P =.03)。此外，双绒毛膜婴儿在新生儿重症监护病房的住院时间较长（30 天[四分位距，18-61] 天 vs 18 天[四分位距，10-35] 天；P =.02）。

结论

无论绒毛膜情况如何，在妊娠 24 0/7 至 31 6/7 周期间通过生长超声检查发现胎儿生长受限且不一致的双胎妊娠，其生出小于胎龄新生儿、早产、早产的可能性几乎是其两倍。与没有不一致的双胎妊娠相比，新生儿发病率更高。妊娠 24 0/7 至 31 6/7 周期间因孤立双胞胎不一致而并发妊娠的患者需要就不良围产期结局进行咨询。