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During pregnancy there is an increased demand for most nutrients for the developing baby as well as the growth of the womb, placenta, blood and other tissues. These demands should mostly be met by a healthy balanced diet, but in practice this may not always be the case.
The actual percentage increase in requirement for many nutrients is between 10% and 50%, however the increase in dietary intake is usually between 10% and 30%. The potential shortfall is reduced by increased absorption as in the case of iron and zinc and reduced losses as in the case of calcium and some other nutrients. This improvement in efficiency of use is often enough, provided that the diet is healthy and nutritious.
Nutritional deficiencies before and in the first trimester of pregnancy are the ones most likely to affect the baby. Those that develop in the last two trimesters of pregnancy are more likely to affect the mother as the placenta is very efficient at concentrating nutrients for the growing fetus.
Nutritional Problems and Pregnancy
- The National Diet and Nutrition Survey of British Adults revealed that women of child-bearing age who are not pregnant may have nutritional deficiencies (anaemia in 8%, folate deficiency 5%, vitamin B12 deficiency 5%, vitamin D deficiency 12% and poor intakes of calcium in 6% and magnesium in 15%). This means that it is likely that a significant percentage of women enter pregnancy with one or more mild deficiencies.
- Between 10% and 15% of pregnancies end in miscarriage, the risk factors for which include poor socio-economic status, obesity, smoking and some nutritional deficiencies as well as genetic factors
- The perinatal mortality rate in the UK remains one of the highest in Europe with 1 in 200 pregnancies ending in stillbirth and 1 in 300 babies dying in the first 28 days of life. The risk factors include social deprivation and thus probably poorer nutritional state, increasing maternal age, binge drinking and ethnicity.
- Neural tube defect pregnancies are more likely if the woman’s balance of folate vitamin is poor and thus all women are advised to commence on a supplement of folic acid (usually 400 ug per day) prior to conceiving as well as eating foods rich in folate. Other possible risk factors include vitamin B12 deficiency and a poor dietary intake of choline.
- All women will have their haemoglobin monitored during the pregnancy and be advised if they need to take iron and folic acid supplements. It is important to note that the normal range for haemoglobin changes in pregnancy. In the UK in pregnant women haemoglobin levels should be at or above 11 g/dl at 16 weeks and at or above 10.5 g/dl at 28 to 30 weeks gestation.
- The recommendation of the Food Standards Agency is that pregnant women who do not receive adequate sunlight exposure have a dietary intake of vitamin D of 10 ug per day. Oily fish and eggs are the main dietary sources and in practice dietary intakes are unlikely to exceed 5 ug per day. Many women will therefore require a supplement of 10 ug of vitamin D daily in pregnancy and this includes most Asian and West Indian women, others with poor sunlight exposure and many women in the winter and spring. www.eatwell.gov.uk/agesandstages/pregnancy/
Those who are in receipt of benefits can receive free supplements. www.healthystart.nhs.uk
- There is no evidence of benefit from the routine use of nutritional supplements by well-fed women with an uncomplicated pregnancy. According to a recent review (2005) women taking multivitamins may be less likely to develop pre-eclampsia and more likely to have a multiple pregnancy but high dose vitamin C may increase the risk. www.cochrane.org/reviews/en/ab004073.html
- Supplements of zinc during pregnancy to those at risk of deficiency may help to slightly reduce preterm births but does not help prevent other problems such as low birthweight babies www.cochrane.org/reviews/en/ab000230.htm
- Those who have significant blood loss at delivery or who were delivered by caesarean section are more liable to develop anaemia and may need to continue iron supplements for three months after delivery
- Women with persistent fatigue in the postnatal period should have their haemoglobin measured and be given appropriate treatment www.nice.org.uk/CG037
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