The Positive Predictive Value of Cerebroplacental Ratio in Determining Adverse Outcome among Post Date Pregnancies

Abstract

Background: Post date or post term pregnancy is relatively a frequent finding in obstetrics. The incidence of post-term pregnancies are reported to in the range of 4-14% with middling value of 10.5%.16 Establishing a safe period to continue pregnancy beyond the calculated estimated due date is not possible and there is little or no agreement among gynecologists at exactly what period the fetus is at risk. There is also controversy that among these post-term pregnancies we can predict the risk of fetal hypoxia accurately. Several researchers have found a statistically significant association of increased perinatal morbidity and mortality among the postdate pregnancies especially after 42 weeks. Various antepartum tests have been proposed for the detection of compromised fetus in post-dated gestations including the Doppler Ultrasonography (USG). Objective: The study objectives were to determine the positive predictive value for Cerebroplacental ratio (CP ratio) of <1.05 as a predictor for adverse pregnancy outcome among these post-term pregnancies in terms of: 

1. Caesarean section for fetal distress.
2. Apgar score of <7at 5mins. 

Patients and Methods: It is a cross sectional study conducted in Department of Obstetrics & Gynaecology, of a Teaching Hospital, Lahore. The duration of the study was six months. Purposive non probability sampling technique was used in present study. Patients with singleton viable pregnancy and ertex presentation as assessed on ultrasound with gestational age exceeding 40 weeks of gestation and Cerebroplacental (CU) ratio of <1.05 were included in this study. Results: We enrolled 250 cases fulfilling the inclusion/exclusion criteria and revealed 17.2% (n=43) cesarean and 14.8% (n=37) had low apgar score, The diagnostic accuracy, specificity, sensitivity, positive predictive value and the negative predictive value of cerebroplacental ration of <1.05 for cesarean section was calculated as 95.6% 93.02%, 97.10%, 86.96%, 98.53% and 96.4% respectively and these values for low apgar score were 86.94%, 97.18%, 84.21%, 97.64% respectively. Conclusion: The study concluded that a high positive predictive value for cerebroplacental ration of <1.05 in predicting adverse outcome in post-date pregnancy in terms of caesarean section for fetal distress and Apgar score of < 7at 5mins which may be used in future for predicting perinatal outcome.