The relationship between maternal serum alpha-fetoprotein and maternal haemoglobin.

OBJECTIVES: To test the hypothesis that both second-trimester maternal serum alpha-fetoprotein (MSAFP) levels and Down syndrome-screening test are related to maternal haemoglobin concentration.

METHODS: Three hundred and seventeen women in three groups according to their haemoglobin levels: normal haemoglobin concentration (between 10.5 and 13.2 g/dL) (n = 262; 82.6%), anaemia (less than 10.5 g/dL) (n = 11; 3.5%), or high haemoglobin levels (greater than 13.2 g/dL) (n = 44; 13.9%) were studied. MSAFP and Down syndrome risk (on the bases of maternal age, MSAFP and maternal serum beta-hCG concentrations) were recorded.

RESULTS: MSAFP (MoM) was lower in women with high haemoglobin levels (0.79 MoM (0.66-1.14)) (p = 0.001) than in women with normal haemoglobin concentrations (1.00 MoM (0.81-1.26)). It was also decreased in women with anaemia (0.90 MoM (0.65-0.94)), even though the difference with women with normal haemoglobin levels was of borderline statistical significance (p = 0.06). The Down syndrome risk was higher in both anaemic women (1:850 (1:380-1:1400)) (p = 0.009) and women with high haemoglobin levels (1:1425 (1:460-1:3100)) (p = 0.036) than in women with normal haemoglobin concentration (1:1950 (1:800-1:5000)). A quadratic model was the best predictive model for both MSAFP (p = 0.02) and Down syndrome risk (p = 0.001) when considering maternal haemoglobin as the independent variable.

CONCLUSIONS: MSAFP is decreased and Down syndrome risk is increased in both anaemic and pregnant women with high haemoglobin concentration. Further studies are needed to establish whether adjustments for maternal haemoglobin are needed when giving Down syndrome risks based on biochemical markers.