Pregnancy supplements 'don’t help, just take vit D a...

"Pregnancy multivitamins are a waste of money because most mothers-to-be do not need them, according to researchers," BBC News reports.

A new report found that only the use of vitamin D and folic acid in pregnancy was supported by the evidence. Whereas expensive multivitamin supplements (often costing around £15 for a month's dose) that combine a wide range of vitamins and supplements, were assessed as being "unlikely to be needed and are an unnecessary expense".

This report summarises a number of systematic reviews and trials on vitamin supplementation in pregnancy. However the report is lacking any explanations of the formal methods used to search and assess the evidence. So we cannot say this is a comprehensive review that assessed all evidence relevant to the use of supplements during pregnancy.

That said, the report chimes with the current official UK advice that women should take 400 micrograms of folic acid each day, from before pregnancy up to 12 weeks, and 10 micrograms of vitamin D daily throughout pregnancy and breastfeeding.

Folic acid is known to reduce the risks of birth defects such as spina bifida and vitamin D may help boost both the mother's and baby's bone and muscle health.

Read more about what vitamins and supplements are recommended during pregnancy.

Where did the story come from?

This was a report in the Drug and Therapeutics Bulletin, part of the BMJ publishing group. The article on vitamin supplementation in pregnancy does not specifically state its authors, their affiliations, or any sources of funding.

This report received wide media coverage in the UK. All media stories mention the current recommendations for pregnant women, but none discuss the reliability of the study, which appears to be a non-systematic review.

Some sources carry a quote from Dr Carrie Ruxton, a dietitian and spokeswoman for trade body the Health Supplements Information Service, who says: "Evidence from the national diet and nutrition survey shows that few women eat the right diet … the role of food supplements is simply to combat dietary gaps".

You could make the case that £15 a month would be better spent of buying cheap, healthy food, as an alternative method of plugging those gaps. Read more about healthy eating in pregnancy.

What kind of research was this?

This was a non-systematic review which summarised the current UK guidance for vitamin supplementation in pregnancy and the evidence it is based on.

As there are no methods provided in this report, we can't be sure the arguments for or against the current guidelines are a good representation of all available evidence. A systematic review including good quality randomised controlled trials would be the best way to form judgements on whether supplementation is worthwhile, however this may be considered unethical in pregnancy.

What did the research involve?

Researchers reviewed studies looking at vitamin supplementation in pregnancy and assessed these against guidelines in the UK. The supplements of interest were:

folic acid
vitamin D
iron
vitamins A/C/E
multivitamins

They provide details of UK guidance from the National Institute of Health and Care Excellence (NICE) for folic acid, vitamin D and vitamin A, however no guidance is given for the other supplements.

The researchers give a summary of their findings for each of the supplements, indicating whether they were based on trial or observational data and the number of people included in the analysis.

The authors did not describe their study inclusion and exclusion criteria, or clearly set out methods. For example, they did not give information on which literature databases they searched, the search dates, search terms, or a description of how studies were quality-assessed and considered for inclusion.

What were the basic results?

NICE recommends women should take 400 micrograms of folic acid each day, from before pregnancy until the end of the first trimester (first 12 weeks), and 10 micrograms of vitamin D daily throughout pregnancy and while breastfeeding. No other supplements are recommended for routine use.

The researchers' findings confirmed NICE recommendations:

Folic acid (400 micrograms) should be taken when trying to conceive and for the first 12 weeks of pregnancy to protect against neural tube defects (NTD), such as spina bifida, in babies. A higher dose of 5 milligrams is suggested for women at higher risk of NTD (e.g. a previous baby with NTD or family history). A systematic review including 6,708 births found that folate reduced risk of neural tube defects (risk ratio (RR) 0.31, 95% confidence interval (CI) 0.17 to 0.58).
Vitamin D (10 micrograms) is recommended throughout pregnancy and breastfeeding. It is thought this helps the baby's bone formation. A number of systematic reviews were reported by the authors, those based on trial data found that a higher concentration of vitamin D was found in the umbilical cord samples of those taking supplements. Some systematic reviews of observational studies have found a possible link between low vitamin D levels and pregnancy or type 2 diabetes, but this link may have been due to confounding. Others have found inconsistent or no effects on other outcomes such as pre-eclampsia, preterm birth or low birthweight baby.
There is no evidence to suggest a need for vitamin supplementation in well nourished women. Vitamin A supplementation should be avoided during pregnancy as it may cause birth defects. Systematic reviews of vitamin C and E have found no evidence of a benefit in the mother or baby. Studies of multivitamins have mostly been carried out in low income countries and so the results can't easily be applied to the UK.
There is also no evidence for routine iron supplementation in all pregnant women as this may cause stomach irritation and constipation or diarrhoea. Pregnant women with low haemoglobin levels need to be investigated and treated as indicated.

How did the researchers interpret the results?

The researchers summarise their findings, saying: "Of the supplements routinely offered to pregnant women in the UK, folic acid has the strongest evidence base".

They go on to say: "the evidence for vitamin D supplementation for all pregnant women is less clear cut, with little randomised controlled trial evidence supporting an effect on clinical outcomes. Nevertheless, a dose of 10µg vitamin D daily is recommended throughout pregnancy and breastfeeding (with a higher dose suggested for some women). For other vitamin supplements, the evidence does not show clear benefit for clinical outcomes for most women who are well nourished. Women should also be advised to avoid taking vitamin A supplements during pregnancy."

They concluded by saying that the primary focus should be on promoting a healthy diet and improving the use of folic acid supplements, which have a poor uptake, particularly among those from lower income families.

Conclusion

This report aimed to assess the current UK guidance for vitamin supplementation in pregnancy and the evidence on which it is based.

Overall the findings are in line with the current recommendations. However, this study cannot be assumed to be a comprehensive systematic review on the effectiveness and safety of vitamins during pregnancy. There is lack of detail on any formal methods and we don't know if the researchers assessed all available evidence on the supplements or whether they have cherry picked ones that fit in with the recommendations.

The researchers suggest a further limitation that many of the studies investigating vitamin supplementation have been carried out in low income countries or among undernourished populations, which does not represent the general population in the UK.

The bottom line here is that the current guideline recommendations have been set for a reason and will have been underpinned by a systematic review and careful appraisal of all relevant research on the issue. This article – though perhaps not systematic – does provide supportive data that those recommendations are doing a good job.

Eating a good, balanced diet during pregnancy, along with folic acid and vitamin D supplements ensures the best possible health for the mother and unborn child.

Read more about diet and the use of supplements during pregnancy.