Vitamins matter

A meta-study links B12 deficiency to low birth weight and premature birth.

Gregory Nemec

Gregory Nemec

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Every year worldwide, nearly one million premature or underweight babies die soon after birth. Reducing that number is one of the most important goals of public health. By reanalyzing existing data, an international team of researchers has taken an important step toward confirming one likely culprit: low levels of vitamin B12.

Scientists know that a malnourished mother is likely to give birth to a smaller baby. But the roles played by micronutrients aren’t always clear. For instance, B12 deficiency in mothers is common, and one might think widespread supplementation would do some good. But studies have contradicted each other on the role B12 plays in premature births and low birth weights. To justify the costs and risks of a randomized controlled trial, let alone a change in guidelines or health policy, researchers need to be reasonably confident that they’re on to something.

So the researchers, including public health professor emeritus Michael Bracken ’70MPH, ’74PhD, systematically reviewed 18 studies of vitamin B12 and preterm births. The team chose an unusual approach to meta-analysis. Instead of pooling all 18 studies’ conclusions—the traditional method, but one that can be hard to apply when the designs of the studies aren’t comparable—they asked the studies’ researchers to provide them with the original raw data sets. The team then reanalyzed individual patient data from ten studies (comprising 8,928 observations in total), along with aggregated data from the other eight. The process is an immense amount of work, but it can yield more-reliable conclusions. (The study appeared in the American Journal of Epidemiology.)

In this case, the data were clear: low maternal B12 levels go hand in hand with low newborn birth weight, and the lower the levels, the likelier the baby will be born early.

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