The study looked at 362 infants and their inner-city mothers after delivery, using maternal serum samples taken back in the first trimester of pregnancy.
The researchers said previous studies had only looked at haemoglobin levels, not specific measures of iron deficiency. In this latest research iron status was assessed by serum ferritin, the transferrin receptor and their ratio, size at birth and whether the baby was born preterm.
Published in the British Journal of Nutrition, the results suggested first trimester maternal iron depletion was associated with a higher risk of the baby being born small for gestational age (SGA). This relationship was even more pronounced when early pregnancy haemoglobin was included, suggesting it was a “mediator”.
The researchers from the University of Southampton, University of Leeds and University of Aberdeen in the UK said the results supported a rethink of how we screen women for iron deficiency, supplement those who are deficient and how nutritional advice is given.
Currently in the UK, routine supplementation of iron in pregnancy is not recommended and pregnant women are only screened for anaemia, which is "final stage" and at the “extreme end” of the iron deficiency spectrum.
They suggested screening for all iron deficiency be provided for women in early pregnancy by testing serum ferritin levels at the first antenatal visit, followed by supplementation when necessary.
Further research on the cost effectiveness of such screening and possible side effects of supplementation was needed, they said.
Until this was done greater emphasis should be put on detailed and helpful dietary advice and ways to optimise nutritional status in pregnancy, including iron intake and absorption from the diet.
“This could be delivered in a personalised fashion as part of the antenatal care package rather than mere signposting to leaflets and information websites.”
Again they said this was likely to have cost implications and should therefore be considered carefully.
Three-fold increased risk
For every 10 g/l increase in maternal haemoglobin level in the first half of pregnancy, the risk of SGA was reduced by 30%. Meanwhile levels below 110 g/l were associated with a three-fold increase in the risk of SGA.
However, there was no evidence of an association between maternal iron depletion and preterm birth.
Of the 362 infants, 64 (18%) were SGA and 33 were born preterm (9% between 34 and 37 weeks).
Maternal haemoglobin in the second half of pregnancy was not associated with SGA risk, which differed from earlier findings.
Source: British Journal of Nutrition
Published online ahead of print, doi:10.1017/S0007114515001166
“Maternal iron status in early pregnancy and birth outcomes: insights from the Baby’s Vascular health and Iron in Pregnancy study”
Authors: N. A. Alwan, J. E. Cade, H. J. McArdle, D. C. Greenwood, H. E. Hayes and N. A. B. Simpson