Fetal Medicine Unit, Medway Maritime Hospital, Gillingham, United Kingdom; Institute of Medical Sciences, Canterbury Christ Church University, Chatham, United Kingdom.
Fetal Medicine Research Institute, King's College Hospital, London, United Kingdom.
Am J Obstet Gynecol. 2019 Jul;221(1):65.e1-65.e18. doi: 10.1016/j.ajog.2019.03.002. Epub 2019 Mar 13.
Third-trimester studies in selected high-risk pregnancies have reported that low cerebroplacental ratio, due to high pulsatility index in the umbilical artery, and or decreased pulsatility index in the fetal middle cerebral artery, is associated with increased risk of adverse perinatal outcomes.
To investigate the predictive performance of screening for adverse perinatal outcome by the cerebroplacental ratio measured routinely at 35-37 weeks' gestation.
This was a prospective observational study in 47,211 women with singleton pregnancies undergoing routine ultrasound examination at 35 to 37 weeks' gestation, including measurement of umbilical artery-pulsatility index and middle cerebral artery-pulsatility index. The measured umbilical artery-pulsatility index and middle cerebral artery-pulsatility index and their ratio were converted to multiples of the median after adjustment for gestational age. Multivariable logistic regression analysis was used to determine whether umbilical artery-pulsatility index, middle cerebral artery-pulsatility index, and cerebroplacental ratio improved the prediction of adverse perinatal outcome that was provided by maternal characteristics, medical history, and obstetric factors. The following outcome measures were considered: (1) adverse perinatal outcome consisting of stillbirth, neonatal death, or hypoxic-ischemic encephalopathy grades 2 and 3; (2) presence of surrogate markers of perinatal hypoxia consisting of umbilical arterial or venous cord blood pH ≤7 and ≤7.1, respectively, 5-minute Apgar score <7, or admission to the neonatal intensive care unit for >24 hours; (3) cesarean delivery for presumed fetal compromise in labor; and (4) neonatal birthweight less than the third percentile for gestational age.
First, the incidence of adverse perinatal outcome, presence of surrogate markers of perinatal hypoxia, and cesarean delivery for presumed fetal compromise in labor was greater in pregnancies with small for gestational age neonates with birthweight <10th percentile compared with appropriate for gestational age neonates; however, 80%-85% of these adverse events occurred in the appropriate for gestational age group. Second, low cerebroplacental ratio <10th percentile was associated with increased risk of adverse perinatal outcome, presence of surrogate markers of perinatal hypoxia, cesarean delivery for presumed fetal compromise in labor, and birth of neonates with birthweight less than third percentile. However, multivariable regression analysis demonstrated that the prediction of these adverse outcomes by maternal demographic characteristics and medical history was only marginally improved by the addition of cerebroplacental ratio. Third, the performance of low cerebroplacental ratio in the prediction of each adverse outcome was poor, with detection rates of 13%-26% and a false-positive rate of about 10%. Fourth, the detection rates of adverse outcomes were greater in small for gestational age than in appropriate for gestational age babies and in pregnancies delivering within 2 weeks rather than at any stage after assessment; however, such increase in detection rates was accompanied by an increase in the false-positive rate. Fifth, in appropriate for gestational age neonates, the predictive accuracy of cerebroplacental ratio was low, with positive and negative likelihood ratios ranging from 1.21 to 1.82, and 0.92 to 0.98, respectively; although the accuracy was better in small for gestational age neonates, this was also low with positive likelihood ratios of 1.31-2.26 and negative likelihood ratios of 0.69-0.92. Similar values were obtained in fetuses classified as small for gestational age and appropriate for gestational age according to the estimated fetal weight.
In pregnancies undergoing routine antenatal assessment at 35-37 weeks' gestation, measurement of cerebroplacental ratio provides poor prediction of adverse perinatal outcome in both small for gestational age and appropriate for gestational age fetuses.
在选定的高危妊娠的孕晚期研究中，发现由于脐动脉搏动指数升高和/或大脑中动脉搏动指数降低而导致的脑胎盘比降低与不良围产儿结局的风险增加有关。
探讨在 35-37 孕周常规测量脑胎盘比筛查不良围产儿结局的预测性能。
这是一项前瞻性观察性研究，纳入了 47211 名单胎妊娠女性，在 35-37 孕周行常规超声检查，包括测量脐动脉搏动指数和大脑中动脉搏动指数。测量的脐动脉搏动指数和大脑中动脉搏动指数及其比值经调整胎龄后转换为中位数倍数。多变量逻辑回归分析用于确定脐动脉搏动指数、大脑中动脉搏动指数和脑胎盘比值是否能改善由母体特征、病史和产科因素提供的不良围产儿结局的预测。考虑以下结局指标：（1）不良围产儿结局包括死胎、新生儿死亡或缺氧缺血性脑病 2 级和 3 级；（2）存在围产期缺氧的替代标志物，包括脐动脉或静脉脐带血 pH 值分别为≤7 和≤7.1、5 分钟 Apgar 评分<7 或新生儿入住重症监护病房>24 小时；（3）分娩时因疑似胎儿窘迫行剖宫产；（4）新生儿出生体重低于胎龄第 3 百分位。
首先，与胎龄适当的新生儿相比，出生体重低于第 10 百分位的小于胎龄儿的不良围产儿结局、围产期缺氧替代标志物的存在以及因疑似胎儿窘迫而行剖宫产的发生率更高；然而，这些不良事件的 80%-85%发生在胎龄适当的组中。其次，脑胎盘比值<10 百分位与不良围产儿结局、围产期缺氧替代标志物的存在、因疑似胎儿窘迫而行剖宫产以及出生体重低于第 3 百分位的新生儿有关。然而，多变量回归分析表明，添加脑胎盘比值仅使这些不良结局的预测略有改善。第三，低脑胎盘比值对每个不良结局的预测效果较差，检出率为 13%-26%，假阳性率约为 10%。第四，在小于胎龄儿中，不良结局的检出率高于胎龄适当的婴儿，在评估后 2 周内分娩的检出率高于任何阶段；然而，这种检出率的增加伴随着假阳性率的增加。第五，在胎龄适当的新生儿中，脑胎盘比值的预测准确性较低，阳性和阴性似然比分别为 1.21-1.82 和 0.92-0.98；尽管在小于胎龄儿中的准确性较好，但阳性似然比为 1.31-2.26，阴性似然比为 0.69-0.92，其准确性也较低。根据估计的胎儿体重将胎儿分类为小于胎龄儿和胎龄适当的儿，得到了类似的值。
在 35-37 孕周行常规产前评估的妊娠中，脑胎盘比值的测量对胎龄适当和小于胎龄儿的不良围产儿结局的预测均较差。
