Department of Obstetrics and Gynaecology, University of Tuebingen, Tuebingen, Germany.
Ultrasound Obstet Gynecol. 2013 Mar;41(3):262-6. doi: 10.1002/uog.12261.
To evaluate the prefrontal space ratio (PFSR) in second- and third-trimester euploid fetuses and fetuses with trisomy 21.
This was a retrospective study utilizing stored mid-sagittal two-dimensional images of second- and third-trimester fetal faces that were recorded during prenatal ultrasound examinations at the Department of Prenatal Medicine at the University of Tuebingen, Germany and at a private center for prenatal medicine in Nuremberg, Germany. For the normal range, 279 euploid pregnancies between 15 and 40 weeks' gestation were included. The results were compared with 91 cases with trisomy 21 between 15 and 40 weeks. For the ratio measurement, a line was drawn between the leading edge of the mandible and the maxilla (MM line) and extended in front of the forehead. The ratio of the distance between the leading edge of the skull and the leading edge of the skin (d1) to the distance between the skin and the point where the MM line was intercepted (d2) was calculated. The PFSR was determined by dividing d2 by d1.
In the euploid and trisomy 21 groups, the median gestational age at the time of ultrasound examination was 21.1 (range, 15.0-40.0) and 21.4 (range, 15.0-40.3) weeks, respectively. Multiple regression analysis showed that PFSR was independent of maternal and gestational age. In the euploid group, the mean PFSR was 0.97 ± 0.29. In fetuses with trisomy 21, the mean PFSR was 0.2 ± 0.38 (P < 0.0001). The PFSR was below the 5(th) centile in 14 (5.0%) euploid fetuses and in 72 (79.1%) fetuses with trisomy 21.
The PFSR is a simple and effective marker in second- and third-trimester screening for trisomy 21.
评估二、三孕期正常胎儿和 21 三体胎儿的前额空间比（PFSR）。
本研究为回顾性研究，利用德国图宾根大学产前医学系和德国纽伦堡私人产前医学中心储存的二、三孕期胎儿面部的中矢状二维图像。正常组纳入 279 例孕 15 周至 40 周的正常胎儿，结果与孕 15 周至 40 周的 91 例 21 三体胎儿进行比较。为了进行比值测量，在颏骨和上颌骨前缘（MM 线）之间画一条线，并在前额前方延伸。计算颅骨前缘与皮肤前缘（d1）之间的距离与皮肤与 MM 线交点（d2）之间的距离的比值。通过将 d2 除以 d1 来确定 PFSR。
在正常组和 21 三体组中，超声检查时的中位孕龄分别为 21.1（范围 15.0-40.0）和 21.4（范围 15.0-40.3）周。多元回归分析显示，PFSR 与母体和孕龄无关。在正常组中，平均 PFSR 为 0.97±0.29。在 21 三体组中，平均 PFSR 为 0.2±0.38（P<0.0001）。14 例（5.0%）正常胎儿和 72 例（79.1%）21 三体胎儿的 PFSR 低于第 5 百分位数。
PFSR 是二、三孕期筛查 21 三体的一种简单有效的指标。
