Thalassaemia trait and pregnancy.

The haematological variables, haematinic state, and placental function of more than 2000 pregnant women, heterozygous for either alpha- or beta-thalassaemia genes, were examined during pregnancy. Four features emerged. Firstly, it was possible by discriminant function analysis of haematological variables to distinguish in pregnant patients between the anaemia caused by thalassaemia trait and that caused by iron deficiency. Secondly, patients with thalassaemia become significantly more anaemic in pregnancy, beta more than alpha, but this was mainly due to plasma dilution. From the data percentile curves were drawn for each type of thalassaemia which predicted the patients' expected "normal" haemoglobin throughout gestation. Thirdly, patients with alpha-thalassaemia had the same incidence of iron deficiency as normal pregnant patients, whereas in those with beta-thalassaemia it was four times less common. The incidence of folic acid and vitamin B12 deficiency was the same in all groups. Finally, as assessed by serum oestriol concentration, there did not appear to be any abnormality of placental function or fetal development associated with maternal thalassaemia, and, also, there seemed to be no increase in maternal or fetal morbidity in pregnancy.