Writing in the journal Systematic Reviews, a team led by Columbia University researchers found that it was uncertain whether birth weight, length and head circumference as indicators of intrauterine growth were improved when women took preconception supplements (iron and folic acid, multiple micronutrients and a lipid-based nutrient supplement).
“The epidemiological evidence for the significance of preconception nutrition is sparse and inconclusive, with a preponderance of animal and observational studies or natural experiments,” the researchers wrote. “To address this knowledge gap, we undertook a systematic review and meta-analysis of the randomized controlled trials (RCTs) assessing the effect of preconception nutrition supplements on maternal anemia and the markers of intrauterine growth.”
Nutrition in resource-poor areas
Low and middle-income countries feel the impacts of impaired intrauterine growth at a rate nearly six times than that of high-income nations. The primary drivers of maternal intrauterine growth are maternal anemia and undernutrition.
Pregnancy places nutritional demands on the mother and fetus, including an increased need for micro and macronutrients to help form the placenta and maternal tissues and promote fetal growth. When these needs are not met, there is an increased risk of maternal anemia, impaired intrauterine growth, preterm births, still births, cognitive delays and neonatal mortality.
For women in countries where these risks are higher, iron and folic acid, multiple micronutrients, macronutrients and nutrient-dense lipid-based supplements may be needed to fill nutritional gaps.
The researchers noted that “among socially disadvantaged women living in food-insecure areas, obtaining a nutritious diet to reduce the burden of maternal anemia and associated impaired fetal growth can be challenging without considering additional nutrition supplements.”
Nutrition supplements do not seem to have a great effect on maternal nutrition during pregnancy, they noted. Instead, the researchers have focused on the preconception period.
“Providing nutrient supplements before conception may be crucial as the preconception window offers an opportunity to intervene for a relatively longer duration to rectify nutrient deficits before pregnancy… a crucial period for laying the foundation for a healthy pregnancy and favorable birth outcomes,” they explained.
Study details
The systematic review and meta-analysis pooled data from 20 randomized controlled trials (RCTs), which included 27,659 non-pregnant women who planned to conceive. When women should receive supplements is debatable, though the study’s findings suggest approximately three months prior to conception. For the studies reviewed, the women consumed supplements including iron and folic acid, multivitamins, multiple micro or macronutrients, or lipid-based nutrient supplements.
The results showed that the preconception nutrient supplements improved maternal hemoglobin by 0.30 g/dL. The preconception period offers women an opportunity to increase their iron stores before planning to get pregnant.
There was no significant effect of supplementation observed on birth weight, length, head circumference, small for gestational age, or preterm birth. The quality of evidence was very low to moderate, the researchers added.
The RCTs showed that women were not given both micro and macronutrients, influencing the efficacy of the supplements that were consumed.
“Without having enough macronutrients, undernourished women may not utilize the nutrients supplied by the micronutrient supplements,” the researchers explained. “Enough macronutrient supply is necessary to meet the energy needs of both the mother and the fetus…Without having energy provided by macronutrients, micronutrients may not be metabolized or transferred across the placenta for fetal growth.”
Source: Systematic Reviews. doi: 10.1186/s13643-024-02726-7. “Role of preconception nutrition supplements in maternal anemia and intrauterine growth: a systematic review and meta-analysis of randomized controlled trials”. Authors: Sumera Aziz Ali et al.
