Ultrasound Unit, Department of Obstetrics and Gynecology, San Juan de Dios Hospital, University of Chile, Santiago, Chile.
Fetal Imaging Unit, FETALMED-Maternal-Fetal Diagnostic Center, Santiago, Chile.
J Matern Fetal Neonatal Med. 2020 Oct;33(20):3469-3475. doi: 10.1080/14767058.2019.1575357. Epub 2019 Feb 10.
To analyze placental vascular resistance and the role of placental insufficiency in the etiology of reduced fetal growth in fetuses with trisomy 21 as determined by umbilical artery (UA) Doppler velocimetry. Second- and third-trimester UA Doppler ultrasound studies were performed in fetuses with trisomy 21 at the time of clinically indicated obstetric ultrasound assessment. The UA pulsatility index (PI) and half-peak systolic velocity deceleration time (hPSV-DT) were measured and recorded. Perinatal outcome was reviewed and the results from UA Doppler velocimetry were compared with birthweight according to gestational age at the time of the delivery. A total of 60 fetuses with trisomy 21 were studied and information from 147 UA Doppler studies was analyzed. Overall, at least one of the UA PI and hPSV-DT values was abnormal in 82% ( = 49) and 90% ( = 54) of the cases, respectively. The incidence of abnormal UA PI values increased with gestational age from 39% (7/18) before 21 weeks to 78% (18/23) after 35 weeks ( < .05). The increase was even more evident for UA hPSV-DT values from 28% (5/18) before 20 weeks to 91% (21/23) after 35 weeks ( < .01). After exclusion of four fetuses with hydrops or isolated hydrothorax/ascites, 16 (29%) were classified at birth as small for gestational age (SGA), 34 (61%) as adequate for gestational age, and six (11%) as large for gestational age, with a mean birthweight -score of -0.36. When only considering the last Doppler ultrasound assessment prior to delivery, UA PI and hPSV-DT values were abnormal in 73% (41/56, mean -score = +1.72) and 82% (46/56; mean -score = -2.18) of the cases, respectively. Mean gestational age at delivery and birth weight were significantly lower in the group with abnormal compared to normal UA PI and hPSV-DT values. Similarly, the incidence of SGA fetuses was significantly higher in the group with abnormal compared to normal UA PI and hPSV-DT values, with 94 ( = 15) and 100% of the 16 SGA newborn infants having abnormal UA PI and hPSV-DT values prior to delivery, respectively. Trisomy 21 fetuses have a progressively higher incidence of abnormal UA impedance indices throughout pregnancy, which suggests developing placental vascular resistance as the pregnancy progresses. This alteration likely begins around the mid second trimester and increases with gestational age; however, increasing placental vascular resistance seems to produce a discrete decrease in fetal growth, despite severe alteration of the UA Doppler impedance indices. As a general hypothesis, we postulate that trisomy 21 fetuses have increasing placental vascular resistance but there may be some factors that protect these fetuses from severe fetal growth restriction.
通过脐动脉（UA）多普勒血流速度测定分析胎盘血管阻力及胎盘功能不全在 21 三体胎儿生长受限中的作用。
对在临床指示性产科超声评估时诊断为 21 三体的胎儿进行第二和第三孕期 UA 多普勒超声检查。测量并记录 UA 搏动指数（PI）和半峰收缩期速度减速时间（hPSV-DT）。回顾围产期结局，并根据分娩时的胎龄比较 UA 多普勒流速的结果与出生体重。
共有 60 例 21 三体胎儿接受了研究，对 147 例 UA 多普勒检查的信息进行了分析。总体而言，82%（49/60）和 90%（54/60）的病例至少有一个 UA PI 和 hPSV-DT 值异常。UA PI 值的异常发生率随胎龄增加而增加，从 21 周前的 39%（7/18）增加到 35 周后的 78%（18/23）（<0.05）。UA hPSV-DT 值的变化更为明显，从 20 周前的 28%（5/18）增加到 35 周后的 91%（21/23）（<0.01）。排除 4 例有水肿或孤立性胸腔积液/腹水的胎儿后，16 例（29%）出生时为小于胎龄儿（SGA），34 例（61%）为适于胎龄儿，6 例（11%）为大于胎龄儿，出生体重 -评分均值为-0.36。仅考虑分娩前最后一次多普勒超声评估，UA PI 和 hPSV-DT 值异常的病例分别为 73%（41/56，平均 -评分=+1.72）和 82%（46/56；平均 -评分=-2.18）。与 UA PI 和 hPSV-DT 值正常的病例相比，分娩时的平均胎龄和出生体重明显较低。同样，UA PI 和 hPSV-DT 值异常组的 SGA 胎儿发生率明显较高，16 例 SGA 新生儿中有 94%（15/16）和 100%（16/16）在分娩前 UA PI 和 hPSV-DT 值异常。21 三体胎儿在整个孕期 UA 阻抗指数异常的发生率逐渐增加，这表明随着妊娠的进展，胎盘血管阻力逐渐增加。这种改变可能在妊娠中期开始，并随胎龄增加而增加；然而，尽管 UA 多普勒阻抗指数严重改变，增加的胎盘血管阻力似乎导致胎儿生长明显减少。作为一个普遍假设，我们推测 21 三体胎儿的胎盘血管阻力增加，但可能存在一些因素保护这些胎儿免受严重的胎儿生长受限。
