The prediction of pregnancy outcome by haemoglobin measurement before 20 weeks` gestation

Maternal haemoglobin levels were measured before 21 weeks' gestation in a prospective study of 1276 singleton pregnancies. Reference ranges were constructed and then applied to a further cohort of 1227 singleton pregnancies to determine the ability of haemoglobin level before 21 weeks' gestation to predict pregnancy outcome. Haemoglobin level decreased significantly with advancing gestational age from 6 to 21 weeks (P < 0.05). Low haemoglobin level was associated with a decreased risk of pregnancy-induced hypertension (adjusted odds ratio 0.51, 95% CI 0.35-0.74). High haemoglobin level was positively correlated with subsequent pregnancy-induced hypertension (P = 0.002) with values > 95th percentile for gestational age having positive and negative predictive values of 33% and 94% respectively. Haemoglobin values (either high or low) were not predictive of proteinuric pre-eclampsia, preterm prelabour rupture of the membranes, preterm birth, low birth weight or the need for neonatal resuscitation of admission to the special care baby unit. The finding of a high maternal haemoglobin before 21 weeks' gestation is not sufficiently predictive of pregnancyinduced hypertension to be of clinical use, but the ability of a low level to predict favourable outcome may be of use in a scoring system designed to identify women suitable for midwifery-based care.