The cerebro- placental ratio as a prognostic factor of fetal outcome in patients with hypertensive states of pregnancy in third trimester at Kenyatta national hospital

Abstract

Introduction Hypertensive states of pregnancy affect maternal and fetal circulations (1). The pathophysiology can be assessed safely and non-invasively by Doppler `ultrasound using arterial Doppler indices of umbilical and middle cerebral arteries thus attaining the cerebro- placental ratio (ratio of the middle cerebral artery resistive index over that of the umbilical artery) (2)

Study Objective This study aimed at determining the role of the cerebro-placental ratio (CPR) as a prognostic factor of fetal outcome in patients with hypertensive states of pregnancy delivered at or after 32 weeks of gestation by dates.

Study Design and Methodology A prospective cohort study carried out at the Kenyatta National Hospital (KNH) over a period of nine months. Gravid patients at least 32 weeks gestations by dates were recruited from labor ward after obtaining informed consent. Consecutive sampling method was used. The cerebro-placental ratio was then calculated. Follow up for fetal outcome, the 5 minute APGAR score and birth weight was made. Ethical Approval was sought from and granted by the Kenyatta National Hospital/University of Nairobi- Ethics and Research Committee (KNH/UoN-ERC).

Problem Statement Fetuses at greater risk of adverse perinatal outcome will have a high resistance umbilical artery waveform and a low resistance waveform of the middle cerebral artery waveform thus a CPR <1

Findings A total of 160 patients were recruited into the study. Median age was 28 years. Sixty two percent (62%) were primiparous. Median gesta tion at admission was 34 weeks while at sonography, the average gestation was 31 weeks Twenty nine percent (29%) had an abnormal CPR (<1.0) while seventy eight percent (78%) had a normal CPR (≥1.0). Seventy eight percent (78%) were delivered via caesarean section while twenty two percent (22%) were delivered vaginally. 51 out of 160 (32%) had severe PET out of which 39% had CPR <1.0 and 61% had CPR ≥1.0. while 109 out of 160 patients(68%) had mild PET out of which 24% had CPR <1.0 and 76% had CPR ≥1.0. Still births were 12.5 times more likely in mothers with CPR <1.0 than those with CPR ≥ 1.0, An APGAR score < 7 was 66 times more often in mothers with CPR < 1.0 than mothers with CPR≥ 1.0. Low birth weight was 4.7 times more likely among mothers with CPR < 1.0.as compared to those with mothers with CPR≥1.0 (95% CI 2, 11.1; p< 0.001). An APGAR score < 7 was 66 times more likely among neonates delivered vaginally as compared to those born via caesarean section(95% CI 1.3, 23; p=0.02) Still births were 14.5 times more often than among neonates born vaginally as compared to those born via caesarean section (95% CI 3, 84; p<0.001).

The prognostic OR for CPR was 12.5 for live births (95% CI 2, 74; p=0.005), 66 for APGAR score <7 (95% CI 13, 340; p< 0.001) and 4.7 for low birth weight (95% CI 2, 11.1; p< 0.001) and 1.1 (95% CI 0.9, 1.4; p=0.327). The prognostic OR of BPPS for live births was 1.7 (95% CI 1.1, 2.5; p=0.009), 1.3 for APGAR score <7 (95% CI 0.9, 1.9; p=0.07) and 1.1 for low birth weight (95% CI 2, 11.1; p< 0.001) and 1.1 (95% CI 0.9, 1.4; p=0.327).

Conclusion CPR is significantly predictive of adverse perinatal outcome when used to monitor mothers with hypertensive states of pregnancy than UA RI or BPPS used alone. CPR was predictive of adverse perinatal outcome (live birth, APGAR score and low birth weight). Caesarian section should be the recommended mode of delivery for hypertensive mothers.