Cerebro placental Ratio (CPR) as an predictor for foetal outcome

 

 

Cerebroplacental ratio (CPR) is an obstetric  ,,ultrasound tool used as a predictor of adverse pregnancy outcome in both small for gestational age (SGA) and appropriate for gestational age (AGA) fetuses. An abnormal CPR reflects redistribution of cardiac output to the cerebral circulation, and has been associated with intrapartum fetal distress, increased rates of emergency cesarean and NICU admissions and poorer neurological outcomes. 

It is calculated by dividing the Doppler pulsatility index (PI) of the middle cerebral artery (MCA) by the PI of umbilical artery (UA) pulsatility index:

CPR = MCA PI / UA PI

The index will reflect mild increase in placental resistance with mild reductions in the fetal brain vascular resistance. An abnormal cerebroplacental ratio may result in the following conditions:

• low normal range MCA and upper normal range UA PI
• abnormal low MCA and normal UA PI
• abnormal low MCA and high UA PI

It follows then that detection of perinatal risk based on CPR may occur in the setting of reassuring UA PI (but abnormal MCA), or even if both UA and MCA PI are within the normal range. The essence of the capacity of a pregnancy to develop normally is that there should be adequate supply of nutrients and oxygen. The principal supply lines are the uterine and umbilical arteries. The utero-placental blood flow has been found to be decreased in hypertensive pregnancies and fetal growth restriction , where instead of the low resistance and high flow state which is seen in normal pregnancies, there is decreased umbilical and uterine blood flow (2).

In antenatal period these small babies can be identified on clinical examination and ultrasonography, but the normal small fetus cannot be distinguished from the compromised small fetus. The Doppler Velocimetry has become an important tool in the evaluation and management of high-risk pregnancies. The umbilical and uterine Doppler abnormalities have been documented in pregnancy complicated by hypertension and fetal growth restriction (3,4). As it can detect abnormal feto-placental circulation, it can be used to differentiate between normal and compromised small fetuses that are at risk of adverse perinatal outcome (5).

The study was conducted with the aims and objectives to study the doppler velocimetric indices of the uterine and umbilical artery in normotensive and hypertensive pregnancy in the third trimester; to detect the number of small for gestational age fetuses with abnormal velocimetric study in each group & correlate the relation of birth weight and Doppler velocimetric findings with perinatal outcome in both the groups.

Material and Methods

The present study was conducted in the Department of Obstetrics and Gynaecology, in collaboration with the Department of Radiology of Mahatma Gandhi Institute of Medical Sciences, Sevagram. A total of 200 cases from the women attending the antenatal outpatient department were included in the study of which 100 were hypertensive and 100 normotensive. All the women had a singleton pregnancy of >32 weeks \gestation and vertex presentation and did not have any history of medical disorder. Both primigravida and multigravida were selected for the study. Among the hypertensive group the women who had recorded blood pressure of >140 / 90 on two or more occasions six hours apart after adequate rest were selected. Baseline investigations and Doppler velocimetry of both the uterine arteries and umbilical artery was performed in both the groups. The patients were followed up till delivery. The perinatal outcome were noted and compared with the results of the Doppler velocimetry.