Fetal Medicine Unit, Department of Obstetrics and Gynecology, University Hospitals Leuven.
Ultrasound Obstet Gynecol. 2013 Jun;41(6):649-52. doi: 10.1002/uog.12387. Epub 2013 May 7.
To establish gestational age-specific reference ranges for amniotic fluid measurements in monochorionic diamniotic twin pregnancies, to compare them with previously reported singleton and twin reference ranges and to examine the rationale for using a gestational age-dependent cut-off to define polyhydramnios in twin-twin transfusion syndrome, as is the practice in most European centers.
We retrospectively evaluated amniotic fluid volume in 32 monochorionic diamniotic twin pregnancies that were followed longitudinally at 2-week intervals from the first trimester until birth. Amniotic fluid volume was assessed by measuring the deepest vertical pocket in both amniotic sacs. We used multilevel modeling to estimate the gestational age-specific reference ranges for deepest vertical pocket measurements.
Based on 429 observations in 64 fetuses, we constructed gestational age-specific reference ranges from 11 weeks until term. The deepest pocket increased from the first trimester to reach a maximum at 26 weeks, followed by a gradual decrease towards term. Measurements between 18 and 28 weeks were comparable to those in singleton pregnancies. However, before 18 weeks values were higher, whereas after 28 weeks they were lower, as compared to singleton references.
In monochorionic twin pregnancies, the deepest vertical pocket is a gestational age-dependent measurement. Therefore, a gestational age-dependent definition of polyhydramnios in twin-twin transfusion syndrome, as used by most European centers, seems a logical approach.
建立单绒毛膜双羊膜囊双胎妊娠羊水测量的特定胎龄参考范围，将其与之前报道的单胎和双胎参考范围进行比较，并探讨在大多数欧洲中心采用基于胎龄的截断值来定义双胎输血综合征羊水过多的合理性，因为这是大多数欧洲中心的惯例。
我们回顾性评估了 32 例单绒毛膜双羊膜囊双胎妊娠的羊水体积，这些妊娠在妊娠早期至分娩期间每隔 2 周进行纵向随访。通过测量两个羊膜囊中最深的垂直囊来评估羊水体积。我们使用多水平模型来估计最深垂直囊测量的特定胎龄参考范围。
基于 64 个胎儿的 429 次观察，我们构建了从 11 周到足月的特定胎龄参考范围。最深口袋从妊娠早期开始增加，在 26 周时达到最大值，然后逐渐减少至足月。18 至 28 周的测量值与单胎妊娠相似。然而，在 18 周之前，值较高，而在 28 周之后，值较低，与单胎参考值相比。
在单绒毛膜双胎妊娠中，最深垂直口袋是一个与胎龄相关的测量值。因此，大多数欧洲中心采用的基于胎龄的双胎输血综合征羊水过多定义似乎是一种合理的方法。
