Simanaviciute D, Gudmundsson S
Kaunas University of Medicine, Lithuania, and Department of Obstetrics and Gynecology, Malmö, University Hospital, Sweden.
Ultrasound Obstet Gynecol. 2006 Nov;28(6):794-801. doi: 10.1002/uog.3805.
To calculate the normal range for the fetal middle cerebral artery (MCA)/uterine artery pulsatility index (PI) ratio in the third trimester of pregnancy and to assess its value, compared with that of the MCA/umbilical artery PI ratio, in predicting an unfavorable outcome of pregnancies complicated by pre-eclampsia.
Doppler blood flow velocimetry of the uterine and umbilical arteries and fetal MCA was performed. We calculated the ratios between 1) the PI of the MCA and the mean PI value of both uterine arteries and 2) the PI of the MCA and the PI of the umbilical artery. All women were examined at or beyond 26 weeks of gestation. A cross-sectional study of 231 normal pregnancies was conducted to construct the reference range. Values below the 5th percentile or an MCA/umbilical artery PI ratio lower than 1.08 were defined as brain-sparing. A further 115 pregnancies with pre-eclampsia (50 mild and 65 severe) were assessed prospectively and the results were related to perinatal outcome. The accuracy of MCA/uterine artery and MCA/umbilical artery PI ratios for prediction of unfavorable pregnancy outcome was compared.
Normal MCA/uterine artery PI ratios decreased with advancing gestational age. Redistribution of the fetal circulation indicated by a low MCA/uterine artery PI ratio was seen in 30% of the mild (n=15) and 46% of the severe (n=30) pre-eclamptic cases. There was a significant difference between those without and those with signs of brain-sparing, respectively, in mean birth weight (2456.0 vs. 1424.5 g), gestational age at delivery (35.6 vs. 31.3 weeks) and gestational age at the time of examination (34.9 vs. 30.9 weeks). Furthermore, there was a significantly higher rate of small-for-gestational-age (SGA) neonates (57.8% vs. 25.7%), preterm delivery (100% vs. 81.8%) and Cesarean section (90.7% vs. 66.7%) in cases with an MCA/uterine artery PI ratio below the 5th percentile. However, there was no difference between the groups in the rate of low 5-min Apgar scores, admission to the neonatal intensive care unit, or deliveries before 34 weeks. The MCA/uterine artery and MCA/umbilical artery PI ratios were similar in the prediction of adverse perinatal outcome. Both ratios were better at predicting the outcome of pregnancy than were signs of increased vascular impedance in either the umbilical or uterine arteries.
Normal MCA/uterine artery PI ratio decreases with gestational age. Abnormally low MCA/ uterine artery PI ratios are related to unfavorable pregnancy outcome. The predictive value of the MCA/uterine artery PI ratio is similar to that of the MCA/umbilical artery PI ratio.
计算妊娠晚期胎儿大脑中动脉（MCA）/子宫动脉搏动指数（PI）比值的正常范围，并评估其与MCA/脐动脉PI比值相比，在预测子痫前期合并妊娠不良结局中的价值。
对子宫动脉、脐动脉和胎儿MCA进行多普勒血流速度测定。我们计算了1）MCA的PI与两条子宫动脉平均PI值之间的比值，以及2）MCA的PI与脐动脉的PI之间的比值。所有女性均在妊娠26周及以后接受检查。对231例正常妊娠进行横断面研究以构建参考范围。低于第5百分位数的值或MCA/脐动脉PI比值低于1.08被定义为脑保护现象。前瞻性评估另外115例子痫前期妊娠（50例轻度和65例重度），并将结果与围产期结局相关联。比较MCA/子宫动脉和MCA/脐动脉PI比值预测不良妊娠结局的准确性。
正常MCA/子宫动脉PI比值随孕周增加而降低。在30%的轻度子痫前期病例（n = 15）和46%的重度子痫前期病例（n = 30）中观察到低MCA/子宫动脉PI比值所指示的胎儿循环重新分布。脑保护迹象阴性和阳性的两组之间，平均出生体重（2456.0 vs. 1424.5 g）、分娩时孕周（35.6 vs. 31.3周）和检查时孕周（34.9 vs. 30.9周）存在显著差异。此外，MCA/子宫动脉PI比值低于第5百分位数的病例中，小于胎龄儿（SGA）新生儿的发生率（57.8% vs. 25.7%）、早产率（100% vs. 81.8%）和剖宫产率（90.7% vs. 66.7%）显著更高。然而，两组在5分钟Apgar评分低、入住新生儿重症监护病房或34周前分娩的发生率方面没有差异。MCA/子宫动脉和MCA/脐动脉PI比值在预测不良围产期结局方面相似。这两个比值在预测妊娠结局方面均优于脐动脉或子宫动脉血管阻力增加的迹象。
正常MCA/子宫动脉PI比值随孕周增加而降低。异常低的MCA/子宫动脉PI比值与不良妊娠结局相关。MCA/子宫动脉PI比值的预测价值与MCA/脐动脉PI比值相似。
