A study suggests that maternal hemoglobin levels in pregnancy may be associated with various maternal and neonatal outcomes. Study results were published in the journal Lancet Haematology.

“Our findings suggest an association between maternal haemoglobin and both maternal and neonatal adverse outcomes,” the study investigators wrote in their report.

The prospective, observational INTERBIO-21st fetal study enrolled pregnant women located in Brazil, Kenya, Pakistan, South Africa, or the UK. Eligible participants began antenatal care prior to 14 weeks of gestation. Routine antenatal blood tests and information related to the pregnancy were evaluated over the course of visits that occurred every 5+1 weeks until the baby’s birth. The researchers analyzed both maternal and neonatal outcomes.

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Several outcomes were considered in conjunction with a maternal hemoglobin concentration of 110 g/L. The study investigators noted that this is the World Health Organization and US Centers for Disease Control and Prevention threshold for characterizing anemia during the first and third pregnancy trimesters.

There were 2069 women included in the study and they had a mean age of 30.7 years (SD, 5.0). Among these women there were 4690 hemoglobin measurements obtained during 14 through 40 weeks of gestation and a median of 3 measurements per participant.

Among maternal outcomes, the risk of pregnancy-induced hypertension occurred appeared to be approximately twice as high for women who had a hemoglobin concentration of 170 g/L, in comparison with a reference threshold of 110 g/L (risk ratio [RR], 2.29; 95% CI, 1.19-4.39). The risk of pregnancy-induced hypertension appeared to be reduced with a hemoglobin concentration of 105 g/L, compared with 110 g/L (RR, 0.88; 95% CI, 0.80-0.96).

The risk of preterm birth was higher among women who had a hemoglobin concentration of 70 g/L, compared with a level of 110 g/L (RR, 2.04; 95% CI, 1.20-3.48).

Preterm birth risk was also higher for women who had a hemoglobin concentration of 165 g/L, compared with 110 g/L (RR, 2.06; 95% CI, 1.41-3.02). A maternal hemoglobin level of 165 g/L was additionally linked to a greater risk among neonates of acute respiratory distress syndrome (RR, 2.84; 95% CI, 1.51-5.35), compared with the reference threshold for hemoglobin.

“The finding of risks relative to haemoglobin concentrations suggests that clinical and public health benefit might arise from using an optimal range of haemoglobin concentrations throughout pregnancy that are associated with lower risk of maternal and neonatal outcomes,” the study investigators stated in their report.


Ohuma EO, Jabin N, Young MF, et al. Association between maternal haemoglobin concentrations and maternal and neonatal outcomes: the prospective, observational, multinational, INTERBIO-21st fetal study. Lancet Haematol. Published online July 20, 2023. doi:10.1016/S2352-3026(23)00170-9

This article originally appeared on Hematology Advisor