New study: insufficient evidence to guide recommendations on vitamin D in pregnancy
Author: Professor Joyce Harper
Today a group from Canada have published a paper in the British Medical Journal which concludes that there is insufficient evidence to guide recommendations on vitamin D in pregnancy. The group undertook a systematic review and meta-analysis of 43 randomised controlled trials.
Up until now, many studies have been published on vitamin D and pregnancy but the results have been conflicting. There is no agreement from the professional bodies about taking vitamin D supplements.
The main results from the new study were that vitamin D increased mean birth weight and reduced the risk of small for gestational age births but findings were not robust. There was no effect on preterm birth but there was evidence that vitamin D reduced the risk of offspring wheeze by age 3 years.
They found that most of the trials on vitamin D and pregnancy were small and of low quality.
They concluded ‘The evidence to date seems insufficient to guide clinical or policy recommendations. Future trials should be designed and powered to examine clinical endpoints, including maternal conditions related to pregnancy (such as pre-eclampsia), infant growth, and respiratory outcomes.’
Thirty five planned/ongoing randomised controlled trials could shed light on vitamin D in pregnancy.
The World Health Organisation (WHO) says “Vitamin D deficiency is thought to be common among pregnant women in some populations, and has been found to be associated with an increased risk of pre-eclampsia, gestational diabetes mellitus, preterm birth, and other tissue-specific conditions.”
WHO say “Vitamin D supplementation during pregnancy improves maternal vitamin D status and may reduce the risk of pre-eclampsia, low birthweight and preterm birth. However, the evidence currently available to directly assess the benefits and harms of the use of vitamin D supplementation alone in pregnancy for improving maternal and infant health outcomes is limited. Pregnant women should be encouraged to receive adequate nutrition, which is best achieved through consumption of a healthy balanced diet.”
But WHO recommends that Vitamin D supplementation is not recommended for pregnant women to improve maternal and perinatal outcomes:
Pregnant women should be advised that sunlight is the most important source of vitamin D. The amount of time needed in the sun is not known and depends on many variables, such as the amount of skin exposed, the time of day, latitude and season, skin pigmentation (darker skin pigments synthesize less vitamin D than lighter pigments) and sunscreen use.
Pregnant women should be encouraged to receive adequate nutrition, which is best achieved through consumption of a healthy, balanced diet, and to refer to WHO guidance on healthy eating.
For pregnant women with documented vitamin D deficiency, vitamin D supplements may be given at the current recommended nutrient intake (RNI) of 200 IU (5 µg) per day.
Read More:
Global Women – Vitamin D – what a huge amount of confusion
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