The danger of high and low haemoglobin levels during pregnancy

Maternal haemoglobin levels that are too low or too high could increase the risk of premature birth and acute respiratory distress syndrome in babies, findings published in The Lancet Haematology show.

Haemoglobin is a protein containing iron that facilitates the transport of oxygen in red blood cells. Almost all vertebrates contain haemoglobin.

According to the lead researcher Eric Ohuma from the London School of Hygiene and Tropical Medicine (LSHTM), the findings are based on data from 2,069 pregnant women in maternity units in five countries: Brazil, Kenya, Pakistan, South Africa and the UK, gathered between 2012-2019.

Dr Ohuma, also an associate professor of Medical Statistics at LSHTM, told Healthy Nation that until now, there has been little evidence that specific haemoglobin thresholds predict health risk or protection for mothers or their children.

“The finding of risks related to haemoglobin concentrations suggests that using an optimal range of haemoglobin concentrations throughout pregnancy could have major clinical and public health benefits, and it’s great to see that this has now been reflected in the revised WHO guidelines,” said the  Kenyan scientist.

According to the researchers, the risk of premature birth more than doubled at haemoglobin concentrations lower than 70 g/L and higher than 165 g/L, and the risk of acute respiratory distress syndrome more than doubled at haemoglobin concentrations of 165 g/L,” the findings highlighted and explained that these levels were compared to the 110 g/L haemoglobin cut-off defined by WHO and the US Center for Disease Control and Prevention .

The study ,which also involved researchers from Emory University, the WHO, and the University of Oxford, further highlighted that increase in risk for premature birth and acute respiratory distress syndrome were found to differ by trimester. The finding for premature birth was only in the second trimester, and for acute respiratory distress syndrome and premature birth it was in the third trimester of pregnancy.

“The risk of pregnancy-induced hypertension more than doubled for women with haemoglobin concentrations of 170 g/L or higher in the third trimester, when compared to 110 g/L. The risk of gestational diabetes was reduced for women with haemoglobin values less than 125 g/L in the second and third trimesters,” they observed.

Senior author of the paper, Dr Jose Villar, a professor at the University of Oxford said, “the study by Young and colleagues revealed a paucity of data linking anaemia to maternal and long-term child health outcomes. They therefore suggested that a longitudinal study needed to be performed with haemoglobin values during pregnancy linked to outcomes to fill this gap. The key strength of our study is that we have met that need, confirming and quantifying the association between maternal haemoglobin concentrations and maternal and neonatal health outcomes.”

 Earlier this year, the “Born too soon: decade of action on preterm birth", a report issued jointly by the World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF) in collaboration with PMNCH, the world’s largest coalition for women, children, and adolescents found that 13.4 million infants globally were born prematurely in 2020, and close to one million of these succumbed to early birth complications. This means that nearly one in 10 babies being born are born before the 37th week of gestation.

“In every two seconds, a baby is born too soon globally, and in every 40 seconds, one of those babies dies.”

The Born Too Soon report further highlights that Kenya is among the countries that have recorded moderately high preterm births (below 10 per cent) with the total number of preterm babies that were born in the country in 2020 being placed at 127,500 out of 1,455,900 children that were born that year. 

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