Relation of haemoglobin levels in first and second trimesters to outcome of pregnancy.

The relation between haemoglobin (Hb) concentrations at antenatal booking and subsequent outcome was examined in 54 382 singleton pregnancies. Both high (greater than 13.2 g/dl) and low (less than 10.4 g/dl) Hb values were associated with an adverse outcome. Mothers with a booking Hb in the intermediate range (10.4-13.2 g/dl) fared best. Significant differences emerged in perinatal mortality between those with high and those with intermediate Hb levels at 13-19 weeks' gestation. The frequencies of perinatal death, low birthweight, and preterm delivery were greater with high than with intermediate Hb. There was a striking relation between booking Hb values and the subsequent frequency of hypertension (p less than 0.001). In primiparas, the frequency of subsequent hypertension ranged from 7% at Hb values under 10.5 g/dl to 42% at Hb concentrations over 14.5 g/dl.