MATERNAL SERUM ALPHA-FETOPROTEIN AND FREE BETA-HUMAN CHORIONIC GONADOTROPIN IN THE SECOND TRIMESTER: IMPLICATION FOR HIGH RISK OF DOWN��?S SYNDROME IN THE GHANAIAN POPULATION

Author(s): Debrah O, Srofenyo E, Aryee NA and IK Quaye

Abstract

Maternal serum screening during pregnancy for adverse changes in levels of alpha-fetoprotein (AFP) and free beta- Human Chorionic Gonadotropin (free β-HCG) in the second trimester to assess risk of Down’s syndrome (DS) is a rare obstetric practice in Ghana. The aim of this study was to determine changes in the levels of these markers, and assess for risk of DS and adverse pregnancy outcomes in the Ghanaian population. Levels of AFP and free β-HCG were determined in maternal serum samples from eighty one women with singleton pregnancy collected at recruitment (12-13 gestational weeks), and in the second trimester (16 gestational weeks). AFP and free β-HCG markers were expressed in multiples of the normal median (MoM) for gestation. Delivery outcomes and features of the new born at delivery were also noted. The mean age of subjects at recruitment was 33.9±3.2 years. AFP levels at recruitment and in the second trimester were 18.8 ± 7.5 ng/ml (mean ± SD) and 30.9 ± 9.8 ng/ml (mean ± SD) respectively. Similarly, free β-HCG at recruitment and in the second trimester were 47.2 ± 12.2 ng/ml (mean ± SD) and 29.8 ± 11.3 ng/ml (mean ± SD) respectively. The differences in the serum levels of AFP and free β-HCG between the first and second trimesters were significant (p<0.0001: 95% CI -14.9-(-9.3) and p<0.0001: 95% CI 13.6-21.2). Whilst the AFP level did not correlate with weight, free β-HCG weakly correlated with maternal weight (p=0.29 and r2=0.017; p=0.08 and r2=0.055 respectively), but not age in the second trimester. There were no cases of DS observed in the study population. The mean concentrations of free β-HCG in adverse pregnancies were higher than in normal pregnancies (38.4 ± 6.6; 29.3 ± 10.6) but not for AFP (p=0.059, and p=0.477 respectively). Although no DS was seen for comparison, free -HCG appears to be a useful marker for risk assessments of poor pregnancy outcomes in the population.

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