Hemoglobin concentration in pregnancy and perinatal mortality: a London-based cohort study.
OBJECTIVE
Failure of fetal growth during pregnancy, and preterm birth, are the major causes of stillbirth and early neonatal death. The objective of the study was to determine the association between maternal hemoglobin concentration during pregnancy and perinatal mortality.


METHODS
The design was prospective, using data on 222,614 first singleton pregnancies in the St Mary's Maternity Information System database in the Northwest Thames region of London.


RESULTS
The association of perinatal mortality with maternal hemoglobin at first antenatal check was not statistically significant (P>.10), but a statistically significant (P<.001) U-shaped pattern was found with lowest recorded maternal hemoglobin concentration. Both early neonatal mortality and stillbirth rates were statistically significantly (P<.005) associated with lowest maternal hemoglobin concentration. The relationship of lowest hemoglobin with early neonatal mortality was largely mediated by the effect of preterm birth, and that between lowest hemoglobin and stillbirth by fetal growth restriction. The lowest perinatal mortality was associated with a lowest recorded maternal hemoglobin concentration of between 9-11 g/dL.


CONCLUSIONS
There is an optimal range of lowest hemoglobin concentration in pregnancy, and on either side of this perinatal mortality is increased. The effect of lowest hemoglobin is largely mediated through associations with preterm birth and fetal growth restriction.
Little
Mark P
MP
Department of Epidemiology and Public Health, Imperial College London, Faculty of Medicine, St. Mary's Campus, Norfolk Place, United Kingdom. mark.little@imperial.ac.uk
Brocard
Pauline
P
Elliott
Paul
P
Steer
Philip J
PJ
D001724:Birth Weight; D015331:Cohort Studies; D016208:Databases, Factual; D005260:Female; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D015994:Incidence; D007226:Infant Mortality; D007231:Infant, Newborn; D007234:Infant, Premature; D016015:Logistic Models; D008131:London / Q000453:epidemiology; D009994:Osmolar Concentration; D011247:Pregnancy / Q000097:blood*; D011256:Pregnancy Outcome / Q000453:epidemiology; D011446:Prospective Studies
D006454:Hemoglobins