Pregnancy and Diet

Pregnancy and Diet

Konstantinos Xenos

Clinical Dietician - Nutritionist M.Sc.

During pregnancy, the dietary requirements of the female body vary greatly in order to provide adequate energy and nutrients to the growing fetus.

The placenta, which weighs 500 grams by the end of pregnancy, transfers nutrients and oxygen from the mother to the embryo. The placenta also transports waste products from the fetal metabolism to the mother, and protects the fetus from high molecular weight nutrients such as most proteins. This leaves the embryo itself to synthesise the proteins from the amino acids it is provided with. The protein IgG is an exception to this rule as it "reaches" the fetus, acts as an immunoglobulin and protects the fetus’ defense system.

It should be noted that the embryo is joined to the placenta by the umbilical cord which consists of 2 umbilical arteries and the umbilical vein.

Before we look into the particularities of the diet for pregnant women, we should stress that the mother should have started eating a proper balanced diet well before she got pregnant. This enables the woman to be in an excellent condition nutritionally and to be capable of supporting the development of the placenta during the initial stage of pregnancy.

The pregnant woman's energy requirements are related to: a) the desired weight gain, which for women starting pregnancy from the correct weight ranges from 11.5 - 16 kg; and b) the increased rate of metabolism which is a result of the pregnancy.
 

Body Mass Index(BMI) is the quotient we arrive at if we divide our weight (in kilograms) by the square of our height (in meters)

Recommended weight gain during pregnancy in Kg

 Women with BMI        <19.8   (Low)
12.5 - 18

                          12,5 - 18

 Women with BMI        19.8 - 26 (Normal)
11.5 - 16

                          11,5 - 16

 Women with BMI        26 – 29   (High)
7 - 11.5

                           7 – 11,5


However, modern scientific evidence points to the need to redefine these recommendations and show that for a woman with a normal body weight that gains 12 kilos during pregnancy, the extra energy needs can be broken down into 90 kcal for the first three months, 285 kcal for the second three months and 465 Kcal for the last three months.These energy requirements are therefore determined as being 300 extra kcal for the last 6 months of the pregnancy, taking into account that the extra calories needed in the first three months by a woman who has been following a proper diet are minimal.

It is essential to note that we are talking about women who do not have to stay in bed during pregnancy, but continue with their physical activity almost as before.

Pregnant women have a particularly high need for protein in the third trimester when maternal and fetal growth rates increase rapidly. At this stage of pregnancy, women need more than 6 grams of protein, more than is required for normal daily needs.

Pregnant women should be especially concerned about the role of essential fatty acids in their diet. This means that it is essential for them to eat fish and nuts frequently.

Indeed, a fatty acid belonging to the Omega−3 family called docosahexaenoic acid plays an essential role in the development of fetus’ healthy nervous system, and many university institutes recommend that pregnant women’s diet should be enriched during the third trimester with reliable sources of this fat (fish, flaxseed and possibly a dietary supplement rich in Omega-3 fat).

Glucose levels can fall more rapidly in pregnant women than in non-pregnant women. This leads to the formation of "dangerous" ketone bodies, and it is therefore recommended that pregnant women never go without food for more than 6 to 8 hours.

The micronutrients which are most important for pregnant women are folic acid, vitamin D, iron and calcium.

Folic acid, a vitamin B complex, plays an important role in the synthesis of DNA.  A low intake of folic acid during pregnancy is associated with an increased chance of developing neonatal neuronal deficits, placental detachment and low birth weight neonates.

It should be noted that the development of the fetal neural tube begins in the very early stages of pregnancy and therefore women should start ensuring that they have a sufficient intake of folic acid early, in fact from when they start planning to become pregnant.

The recommended daily intake of folic acid during pregnancy is 600 micrograms. It is difficult to meet this recommendation exclusively from good dietary sources (dark green leafy vegetables, pulses, orange juice, some fortified cereals) so, taking into account that folic acid is "difficult" to absorb, it is often recommended that women take a supplement containing 400 micrograms of folic acid.

Vitamin D is known to be necessary for calcium absorption and for bone resobption. A lack of this vitamin during pregnancy is associated with hypocalcaemia in the newborn. Good sources of vitamin D include oily fish, vitamin-enriched products such as breakfast cereals, soft margarines and dairy products In addition, exposure of the hands, face or feet to the sun 2-3 times a week (15 minutes) is considered to provide enough Vitamin D.

It is well known that iron is used to synthesise hemoglobin, which is absolutely essential to transport oxygen in the blood. It is necessary to increase iron intake during pregnancy to cover both the increase in blood volume during pregnancy and the needs of the fetus and the placenta. The fetus 'takes' a lot of iron from the mother, especially in the last three months of pregnancy. This is nature’s way of looking after the child, as the breast milk that will soon become the child’s exclusive food is low in iron.

At 12 weeks, pregnant women should start increasing their iron to the recommended amount of 30 mg daily.

Although iron absorption (as well as calcium absorption) increases during pregnancy, it appears that good sources of iron, such as red meat, poultry and egg, are often inadequate and pregnant women often need to take a ferrous fumarate supplement. The precise amount of iron needed is arrived at by examining a blood sample given by the pregnant woman. Eating liver, which is an excellent source of iron, is not recommended as it contains an excessive amount of vitamin A, which can lead to the baby being born with microcephaly and kidney problems.

The mother should have sufficient calcium during her pregnancy, as this has a very important effect on the child’s bone density which develops later on.

The recommended amounts are 1000 mgr for women over the age of 18. The body naturally develops an adaptive mechanism during pregnancy which greatly increases calcium absorption, especially during the third trimester of pregnancy, and at the same time reduces its excretion. With the help of this mechanism, women who are eating properly can meet their calcium requirements without the help of a supplement.

A glass of milk, a yogurt or 1 ½ slice of yellow hard cheese contain about 300 mg of calcium.

In conclusion, it should be emphasised that a balanced diet plan for pregnant woman, should include low intakes of coffee and salt for precautionary purposes.

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