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 Overall, mothers who took vitamin D during pregnancy were 28 percent
less likely to have underweight newborns or babies who died in the
womb or during infancy, the study found.
But prenatal vitamin D supplements only appeared to have these
benefits when women took 2,000 International Units (IU) or less each
day. This amount of vitamin D was tied to 55 percent lower odds of
an underweight baby and 65 lower chance of a baby dying in the womb
or during infancy.
At higher doses, any differences between women who took vitamin D
and those who didn't were too small to rule out the possibility that
they were due to chance.
Taking vitamin D during pregnancy was safe, with no extra fetal or
neonatal mortality, congenital abnormality, or critical illness at
birth, said senior author Dr. Shu Qin Wei of the University of
Montreal, Canada. And supplementation reduced infants' risk of being
small for gestational age and improved their calcium levels and
growth in the first 12 months of life.
"Moreover, we found that the lower dose of vitamin D supplementation
(up to 2,000 IU a day) reduced risk of fetal or neonatal mortality
and infants being small for gestational age, but higher doses (more
than 2,000 IU a day) did not reduce the risk of perinatal mortality
and infants being small for gestational age," Wei said by email.
Vitamin D deficiency during pregnancy is common worldwide,
researchers note in JAMA Pediatrics. Vitamin D contributes to a wide
range of processes during fetal development including bone growth,
muscle function and healthy fat accumulation as well as heart
function, neurodevelopment and immune responses, Wei said.
Beyond pregnancy, many older adults take vitamin D to promote bone
health. Too much of this supplement can lead to harmful accumulation
of calcium in soft tissues such as the heart and kidneys.
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For the current study, researchers analyzed data from 24 clinical
trials including a total of 5,404 participants.
They didn't find a meaningful difference in birth defects based on
whether mothers took vitamin D during pregnancy. They also didn't
find any link between prenatal vitamin D supplementation and babies'
risk of asthma.
One limitation of the study is that researchers lacked data on
long-term health outcomes for mothers or babies, since the longest
clinical trial in the analysis lasted only three years and many of
the other trials were much shorter.
Still, the results should reassure pregnant women about the benefits
of taking vitamin D, said Dr. Bo Chawes, author of an accompanying
editorial and a researcher at the University of Copenhagen in
Denmark.
"We already knew that vitamin D supplementation prevents development
of rickets, which is a bone disorder resulting in weak bones and an
increased risk of fractures, but we did not know if increasing the
supplement had an effect on intrauterine or postnatal growth in
early childhood," Chawes said by email.
"The most interesting and robust finding of the meta-analysis is
that increased supplement is safe for the child and may reduce the
risk of being born small for gestational age, which is associated
with an increased risk of perinatal and neonatal mortality and
morbidity," Chawes added.
SOURCE: http://bit.ly/2kyKlsj JAMA Pediatrics, online May 29, 2018.
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