Department of Obstetrics & Gynaecology, St George's, University of London, London, UK.
Ultrasound Obstet Gynecol. 2009 Jul;34(1):38-42. doi: 10.1002/uog.6422.
To assess whether early fetal growth restriction in a twin, expressed as the intertwin discrepancy in crown-rump length (CRL) between two viable twins at 7 + 0 to 9 + 6 weeks' gestation, is predictive of subsequent single fetal loss.
This was a retrospective analysis of data collected prospectively over 3 years. Women attending an early pregnancy unit underwent a transvaginal ultrasound examination. In women with a viable twin pregnancy between 7 + 0 and 9 + 6 weeks of gestation, the CRL ratio between the two embryos was calculated. Women were followed up and the intertwin discrepancy in CRL at the 7 + 0 to 9 + 6-week scan was compared between cases in which there was spontaneous reduction to a singleton and those in which both twins remained viable at the 11-14-week scan.
There were 77 women included in the study and nine (12%) of these had a single fetal loss. Pregnancies with subsequent single fetal loss were more likely to have a larger median CRL discrepancy (42.0%; interquartile range (IQR), 23.8-64.3%) than were those which retained two viable fetuses (6.1%; IQR, 2.2-12.5%) (P < 0.0001). The median CRL discrepancy in subsequently viable monochorionic diamniotic twins (10.9%; IQR, 1.9-17.5%) was no different from that in dichorionic diamniotic twin pregnancies (5.9%; IQR, 2.1-12.3%) (P = 0.305). Regardless of chorionicity, there was a relationship between increasing CRL discrepancy and single fetal loss; the likelihood of a subsequently viable twin pregnancy was 97% if the discrepancy was < 20%, while if the discrepancy was > 60% there were no cases of both twins remaining viable (P < 0.0001). Receiver-operating characteristics curve analysis of CRL discrepancy in predicting single fetal loss gave an area under the curve of 0.93, with an optimum cut-off point of 16.9% discrepancy (sensitivity, 88.9%; 95% CI, 51.8-99.7; and specificity, 86.7%; 95% CI, 76.3-93.8).
There is a significant relationship between CRL discrepancy at 7 + 0 to 9 + 6 weeks and the likelihood of subsequent single intrauterine fetal loss. This suggests that spontaneous fetal demise of one twin may be preceded by growth restriction in the first trimester.
评估双胞胎在 7+0 至 9+6 周妊娠时的头臀长（CRL）之间的双胞胎间差异是否可预测随后的单胎胎儿丢失。
这是一项对 3 年内前瞻性收集的数据进行的回顾性分析。在妊娠早期单位就诊的女性接受经阴道超声检查。在 7+0 至 9+6 周妊娠时存在存活双胞胎的女性中，计算两个胚胎的 CRL 比值。对女性进行随访，并比较 7+0 至 9+6 周扫描时双胞胎间 CRL 差异在自然减少为单胎的病例和 11-14 周扫描时仍存在两个存活胎儿的病例之间的差异。
本研究共纳入 77 名女性，其中 9 名（12%）发生单胎胎儿丢失。随后发生单胎胎儿丢失的妊娠更可能存在较大的中位数 CRL 差异（42.0%；四分位距（IQR），23.8-64.3%），而非保留两个存活胎儿的妊娠（6.1%；IQR，2.2-12.5%）（P<0.0001）。随后存活的单绒毛膜双羊膜囊双胎（10.9%；IQR，1.9-17.5%）的 CRL 差异中位数与双绒毛膜双羊膜囊双胎妊娠（5.9%；IQR，2.1-12.3%）无差异（P=0.305）。无论绒毛膜性如何，CRL 差异与单胎胎儿丢失之间均存在关系；如果差异<20%，随后存活的双胞胎妊娠的可能性为 97%，而如果差异>60%，则不存在两个胎儿均存活的情况（P<0.0001）。CRL 差异预测单胎胎儿丢失的受试者工作特征曲线分析显示曲线下面积为 0.93，最佳截断点为 16.9%差异（敏感性，88.9%；95%CI，51.8-99.7%；特异性，86.7%；95%CI，76.3-93.8%）。
7+0 至 9+6 周时 CRL 差异与随后单胎宫内胎儿丢失的可能性之间存在显著关系。这表明，一个胎儿的自发性死亡可能在孕早期就出现生长受限。
