Relation between maternal haemoglobin and placental hormone concentrations in early pregnancy

Environmental factors that influence placental development are of particular interest because of the reported association between adult hypertension, low birthweight, and large placental size. Maternal anaemia is one environmental factor that is associated with an increase in placental size at birth. We have examined the relation between haematological status and plasma concentrations of chorionic gonadotropin (hCG) and placental lactogen (hPL) in 175 women at about 10 weeks of pregnancy. There were significant negative correlations between maternal haemoglobin concentration and the levels of hCG (p = 0.03) and hPL (p = 0.02). Although 21% of women had low iron stores (ferritin < 13 micrograms/L), no relation was found between serum ferritin and the two placental hormones. There was no association between plasma volume (calculated from maternal weight and height) and hCG or hPL concentrations. We conclude that our observations reflect an influence of the maternal environment on the placenta. The fact that negative correlations with placental hormone concentrations exist across the normal haemoglobin range suggest that they reflect a normal aspect of placental development. We speculate that placental growth is, in part, determined by maternal factors that prevail before conception. One possibility is that these factors modify angiogenesis within the trophoblastic villi.