Intrapartum complications are a major contributor to adverse perinatal outcomes and significant neonatal morbidity [15]. The compromised fetuses frequently require rapid delivery by emergency operative delivery that carries considerably more maternal risk than less urgent procedures. Neonatal outcomes are also significantly poorer following emergency caesarean for fetal distress [6].
The most widely used screening method for intrapartum hypoxia is electronic fetal heart rate monitoring. It has very poor specificity and positive predictive value for hypoxia and adverse neonatal outcome [16].
Vulnerable fetuses often require rapid delivery by emergency cesarean section, which carries elevated maternal and fetal risks, and costs the healthcare system much more than vaginal delivery. The recent the UK Royal College of Obstetricians and Gynaecologists’ Each Baby Counts Report reveals that 0.16% of all term babies born in 2015 died or suffered significant brain injury following the onset of labor. In conjunction with other recommendations, this report highlights the need for continuous risk assessment commencing in the antenatal period and continuing intrapartum [17].
The current challenge is therefore to identify vulnerable fetuses at risk of hypoxic complications, particularly within an apparently low-risk cohort before the onset of labor.
The cerebroplacental ratio, a ratio of the middle cerebral artery PI and umbilical artery PI, is widely considered to be more indicative of adverse neonatal outcome than the assessment of blood flow indices individually [18].
We conducted this study aiming at assessing the fetal cerebroplacental ratio for prediction of adverse intrapartum and neonatal outcomes in a term, uncomplicated pregnancy.
One hundred fifty patients were included in the study, and participants were subjected to detailed history, physical examination, and ultrasound examination and were allocated into two groups according to CPR ratio with values below 1.1 as abnormal [19]. Afterwards, parameters characterizing the course of labor and the newborn’s status were correlated with abnormal Doppler results.
The mean age of the participant’s females was 29.2 ± 4.1 years. More than half the sample was housewives (53.3%). About 58.7% of the females came from rural areas and only 11.3% had a high socioeconomic status. About 72% had vaginal delivery while about 28% underwent cesarean section and 17% of them due to intrauterine fetal comprise.
Patients with CPR less than 1.1 were 16.7% and those with CPR more than 1.1 forms 83.3. There was no significant association between CPR with baseline and clinical characteristics of the pregnant females.
On assessing the association between rate of emergency cesarean section and CPR ratio, we found a significant increase in the prevalence of emergency cesarean sections in the group with CPR ratios < 1.1 (40% vs. 25.6%). An abnormal CPR had a six-fold increased odds of cesarean section for inrapartum fetal compromise. The AUC values for cesarean sections for intrapartum fetal compromise (0.837) are considerably higher than those reported for intrapartum fetal heart rate monitoring (0.60–0.63) [20].
In a subsequent study published 2015, Khalil et al. examined 8382 patients who underwent Doppler ultrasound examination after 37 weeks of gestation to evaluate the association between fetal cerebroplacental ratio (CPR) and intrapartum fetal compromise and admission to the neonatal unit, and their study showed that in fetuses requiring an emergency cesarean delivery for fetal distress, an abnormal CPR was significantly more frequent (13.1% vs 9.4%; P < .001) than those not requiring operative delivery [21].
Prior et al. prospectively evaluated 400 fetuses at term and reported that the CPR was shown to be an independent predictor of CS for intrapartum fetal compromise, and an abnormal CPR was found in 11%. Of those who underwent cesarean delivery for fetal distress, 36.4% had an abnormal CPR compared with 10.1% (p < .001) that had a normal CPR. A low CPR ratio was associated with a six-fold increased rate of cesarean section for presumed fetal compromise. An abnormal CPR was a better predictor for an emergency cesarean delivery than an abnormal middle cerebral artery or umbilical artery [22].
In a study reported by Rosello et al., who evaluated the CPR in fetuses between 37 and 41.9 weeks of gestation, they found that the UA and venous pH were significantly lower in newborns who had an abnormal CPR than fetuses with a normal CPR. These data suggest that the CPR could be used to assess the risk of intrapartum fetal distress requiring cesarean delivery [23].
Another study conducted by Bligh et al. on 207 women with term uncomplicated pregnancy who studied the screening performance of low fetal cerebroplacental ratio and maternal placental growth factor level, for the prediction of cesarean section for intrapartum fetal compromise, reported that pregnancies delivered by CS for IFC had significantly lower mean CPR than the rest of the study cohort [24].
Women at a significant risk of IFC and/or adverse neonatal outcome could be offered elective birth when staff levels and availability of operative procedures are optimal. This could potentially reduce the number of emergency cesarean section procedures performed, thus improving maternal and neonatal outcomes.
In the current study, we found that infants with an abnormal CPR ratio had a significantly higher incidence of CTG abnormalities than those with a normal CPR ratio (80%) vs (12.8%), respectively, and that the likelihood of the having an abnormal FHR was increased more than twenty-seven-fold with abnormal CPR.
In the line of our study Ropaka et al. who studied the usefulness of Doppler velocimetry, based on cerebroplacental ratio evaluation, in predicting intrapartum fetal heart rate abnormalities and adverse neonatal outcome in 148 women with uncomplicated pregnancies at 40–42 weeks reported that the percentage of abnormal CTG records in group with abnormal CPR (62.3%) was significantly higher when compared to group with normal CPR (19.0%) [25]. Prior et al. also reported that infants with a low CPR ratio had significantly higher rates of CTG abnormalities when compared with infants with a normal CPR ratio (82% vs 31%) [22].
We found that there was a significant relation between CPR and low Apgar score. Neonates with CPR <1.1 had significantly lower Apgar score at 1 min and 5 min than those with CPR >1.1 (36% vs 11.2%) and (20% vs 2.4), respectively. Pregnancies with CPR <1.1 were 4.46 times more likely to have 1-min Apgar score <7 for neonates than those with CPR >1.1.
Prior et al. reported that Apgar scores <7 at both 1 min (56.5 vs 5.1% ) and 5 min (27.5 vs 1.3%) were significantly lower with a low pre-labor CPR and described a greater frequency of poor Apgar scores in the low CPR group, but these did not reach significance [22].
Ropacka-Lesiak et al. also reported 1- and 5-min Apgar score to be significantly lower in patients with abnormal CPR when compared to the control group [25]. Meanwhile, Prior et al. 2013 reported no significant difference in the incidence of Apgar score <7 at 5 min between the CPR ratio percentile groups [22].
In addition, in this study, the rate of NICU admission was observed to be significantly higher in neonates with CPR <1.1 than those with CPR <1.1 (32 vs. 8.8%) respectively, and that the odds of being admitted to NICU is 4.87 times greater for neonates who have CPR ≤1.1 vs. those who have CPR >1.1.
In the line of our study, Khalil et al. reported the rate of NICU admission to be higher in group with abnormal CPR 14.3% vs 9.7%, while Prior 2013 described no significant difference in the rate of neonatal unit admission between the CPR ratio percentile groups [21].
Our result suggested that the cut-off value of CPR 1.1 is a reliable value to predict adverse intrapartum and neonatal outcomes, which is consistent with the value of 1.1 recommended by Arbeille et al. and DeVore.
Evaluation of the performance of CPR revealed that it has (63%) sensitivity, (71%) specificity, and (70%) accuracy, and the positive and negative predictive values were (24) and (93), respectively.
Previous studies on CPR have provided conflicting reports on its test performance. Murata et al. found that CPR with cut-off value of 1.1 had 62% sensitivity and 74.5% specificity to predict adverse outcome [26]. Prior et al. reported that a low CPR is associated with increased risk of emergency operative delivery for IFC (sensitivity 32.5%, specificity 93.2%, and positive predictive value 36.4%) [22]. Devine et al. obtained contrasting results. They suggested CPR values below 1.05 to be a good predictor of adverse perinatal outcome in post-term pregnancies, but the study included a number of high-risk pregnancies complicated by hypertension or gestational diabetes [27].
In contrast, Bakalis et al. reported using retrospective data in an unselected population, CPR measured at 30–34 weeks’ gestation was shown to be a weak predictor of perinatal complications, with detection rates of 5–11% and 20–50% when measured >2 weeks and <2 weeks from delivery, respectively [28].
There are few reports regarding the screening efficiency of the cut-off value of CPR. It may be difficult to determine the fixed cut-off value of CPR for screening because CPR changes depending on gestational ages during pregnancy. Taken into consideration, the reports that summarize the data by Baschat and Genbruch, our cut-off value of CPR 1.1 seems to be appropriate for clinical application in term uncomplicated pregnancy [29]. Some authors suggest that reference ranges should be applied for the CPR assessment. However, there are studies which revealed no superiority of reference ranges over cut-off values with regard to adverse perinatal outcome prediction [30, 31].
Gramellini, as well as other researchers, reported that CPR values are constant throughout the last 10 weeks of pregnancy. That is why the value of 1.1 was established as a cutoff point, and values < 1.1 were reported as abnormal [32].
The current study showed that the cerebroplacental ratio had a sensitivity of (63%) which represents an advance on current practice, in which up to 60% of births complicated by intrapartum compromise occur in pregnancies with no apparent antenatal risk factors [2].
