This week I’ve been working outside Toronto, and today found my eye diverted by a story on the front cover of the Canadian Globe and Mail about the use of nutritional supplements in pregnancy. The research, published in the Journal of Obstetrics and Gynaecology of Canada (1) was a meta-analysis of studies in this area (a meta-analysis combines the results of several studies to assess the effect of a treatment or approach). This research, which originated just down the road at the Toronto Hospital for Sick Children, revealed that taking a multivitamin and mineral prior to pregnancy was associated with:
- A 48 per cent reduced rate of what are known as neural tube defects (such as spina bifida)
- A 39 per cent reduced rate of cardiovascular defects (such as abnormalities of the heart)
- A 47 per cent lower rate of leg deformities
- A 58 per cent reduction in the rate of cleft palate
- A 52 per cent reduction in the rate of urinary tract defects (such as kidney and bladder problems)
- A 63 per cent reduction in the rates of hydrocephalus (a condition in which the pressure of fluid in skull is increased, which can lead to enlargement of the head and brain damage)
Most women will be all too aware of the benefits of taking folic acid before pregnancy, and for at least the first three months of pregnancy: several studies have shown that this has the capacity to dramatically cut the risk of neural tube defects. What this study shows is that taking a wide range of nutrients (in addition to folic acid) has the capacity to help prevent a several different types of birth defect. Because abnormalities of the foetus usually develop early on in pregnancy, supplementation with nutrients should ideally be started some time before the actual pregnancy. The authors of this study therefore recommended that all children of child-bearing age would do well to take a multivitamin and mineral designed specifically for pregnancy. Ideally, such a supplement should contain useful, but not excessive quantities, of a wide range on vitamin and minerals. Such a supplement should also contain relatively low levels of vitamin A ” a nutrient which in excess has been associated with an increased risk of birth defect. For more information about the benefits of nutritional supplementation in pregnancy, see the attached article:
A Guide to Supplementation Prior to Pregnancy
Research shows that good intakes of certain nutrients, notably folic acid, help to maintain a healthy pregnancy and reduce the risk of abnormalities. However, risk of the formation of birth defects is greatest during the very early stages of pregnancy. Often, it is some weeks before a woman realises she is pregnant. Supplementation at this state may be beneficial, but may also have missed the time when adequate levels of certain nutrients are most critical. What this means is that, for the best protection, supplementation should be started before conception.
Which nutrients are most important?
Folic acid, perhaps more than any other nutrient, is recommended for pregnant women. One of folic acid’s chief roles is to ensure the normal functioning of DNA: the component in the body’s cells that carries our genetic code. Normal function of DNA is especially important during pregnancy. If DNA goes awry at this time, problems with the development of the foetus are more likely. By helping to ensure DNA does its job without mishap, folic acid helps reduce the risk of genetic problems such as spina bifida (failure of the spinal column to close during development) and anencephaly (abnormal development of the skull and/or brain). These sorts of problems are collectively referred to as neural tube defects (NTDs). One study found that folic acid supplementation reduced the incidence of neural-tube defects by 70 per cent (2).
NTDs form early in pregnancy – within a month of conception, which is why it’s important, if possible, to start supplementation of this nutrient prior to pregnancy. Currently, the recommended daily intake of folic acid for women is 400 µg (micrograms). For women who have a previous history of having a child with an NTD, 5 mg (5000 mcg) per day is recommended.
Folic acid is not the only important nutrient during the early development of the foetus. Other nutrients that are involved in DNA function include vitamin B12 and zinc. A deficiency in the nutrient copper in early pregnancy also seems to have the potential to cause abnormalities (3). Another nutrient that seems to have an important role in pregnancy is selenium – levels of which have fallen significantly in the UK diet in recent time. There is some evidence that selenium deficiency may contribute to miscarriage (4).
While the core nutritional approach to preparing for a healthy pregnancy is best centred around a healthy diet, there seems little doubt that supplementation offers considerable benefits too. Unfortunately, our diet cannot always be relied upon to give us optimal amounts of nutrients. Over the last 60 years the vitamin and mineral content of foods such as fruits and vegetables has shown a distinct downward trend. Intensive farming methods, the extensive use of agrochemicals, and modern ripening and storage systems appear to be eroding the nutritional content of our diet. The average consumption of the trace mineral selenium, for instance, has fallen by a third in the last 30 years alone. Government statistics show that significant numbers of women are not getting enough of essential nutrients such as folic acid, copper, zinc, vitamin A, vitamin C, calcium, magnesium, iron or iodine in their diets.
In studies, multi-nutrient supplementation has been found to have a range of positive effects on the outcome of pregnancy. One study examined the effects of giving a variety of nutrients starting three months prior to conception, and continuing for the first few months of pregnancy (5). This research found several benefits which included:
- Significantly reduced risk of neural tube defects
- Significantly reduced risk of defects in the urinary tract (e.g. the kidneys and bladder)
- Significantly reduced risk of cardiovascular defects (such as heart defects)
- A reduced rate of limb deficiencies
- A reduced risk of a condition known as congenital hypertrophic pyloric stenosis (a condition in which the outlet to the stomach becomes blocked in the first few weeks of life causing projectile vomiting and dehydration)
Another study found that women who took vitamin and mineral tablets before and during pregnancy appeared to reduce the risk that their baby will develop a certain type of cancer of the nervous system called neuroblastoma (6). Daily vitamin and mineral use in the month before pregnancy and throughout pregnancy was associated with a 30 ” 40 per cent reduction in the risk of this cancer.
Vitamin A in pregnancy
There is some evidence in the scientific literature that supplementing with vitamin A at doses of around 3000 mcg a day or more during pregnancy may increase the risk of birth defects (7). However, more recent evidence suggests that vitamin A can be taken in higher doses quite safely (9). Nevertheless, it seems the most sensible thing to do is err on the side of caution with this. I recommend that women who are pregnant or planning pregnancy should not supplement with vitamin A at doses exceeding 3000 mcg (10,000 IU) per day.
References:
1. J Obstet Gynaecol Can 2006;28(8):680-689
2. MRC Vitamin Study Research Group. Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. Lancet 1991;338:131-137
3. Keen, C.L. et al. 1998. Effect of copper deficiency on prenatal development and pregnancy outcome. Am J Clin Nutr. 67(suppl5):1003-1011
4. Barrington, J.W. et al. 1996. Selenium deficiency and miscarriage: a possible link? Br J Obs Gynaecol. 103:130-132
5. Czeizel A. Periconceptional folic acid containing multivitamin supplementation. European Journal of Obstetrics and Gynecology and Reproductive Biology. 1998 78:151-161.
6. Olshan AF et al. 2002. Maternal vitamin use and reduced risk of neuroblastoma. Epidemiology. 13:575-580
7. Rothman KJ, et al. Teratogenicity of high vitamin A intake. N Engl J Med 1995 333(21):1369-1373
8. Mills JL, et al. Vitamin A and birth defects. Am J Obstet Gynecol 1997 177(1):31-23; Miller RK, et al. Periconceptual vitamin A use: how much is teratogenic? Reprod Toxicol 1998 12(1):75-88
