Nutrition For Pregnancy
During the past 40 years, recommendations for ideal weight gain and nutrient intake to effect a healthy pregnancy have changed. In the 1960s, studies focused on the benefits of appropriate weight gain in the 2nd and 3rd trimesters of pregnancy to produce healthy babies. This was coupled with reports that low weight gain resulted in infants being at higher risk for developmental problems and mortality. This has resulted in many reports since the 1970s recommending higher gestational weight gain and monitored nutrient intake for pregnant women. However, despite these reports, consensus on recommendations has been lacking.
Why Is Prepregnancy Weight Gain So Important?
Prepregnancy weight-for-height is the simplest, most useful index for evaluating pregnancy nutrition status. It is expressed as a percentage of a standard and provides a systematic method for distinguishing women who weigh more because of height or weight, extra fat or lean body mass.
Recommendations are that weight goals for pregnancy be individualised according to prepregnancy weight-for-height and based on the average weight gain known to result in full-term babies weighing 6½ pounds. Listed below are some weight gain ranges for women of various prepregnancy weights-for-height. These reflect the wide variations in weight gain during normal pregnancies.
As a Percentage of Standard*
Recommended Weight Gain Range
Normal Weight 100%
Normal Weight 100%
*Percentage of standard weight = Observed weight / desirable weight (based on height) x 100
*1959 Metropolitan Life Insurance Weight Tables used for desirable weight calculation.
For most women, weight gains of at least the lower end of the listed ranges should be encouraged. Registration with a registered dietician is advised to ensure that the pregnant woman eats a balanced diet whilst trying to achieve this goal. There are certain groups of women who will need to be encouraged to gain weight at the higher end of the range because they tend to have smaller babies in relation to the amount of weight gained. These include African-American women, underweight women and young adolescents (less that two years post menarche). Higher weight gain, especially in short women (under 5'2") is associated with increased birth weights and some increased risk at delivery. Due to this, weight gains at the lower end of the scale are recommended for women of short stature.
For women carrying more than one child, the average gestational weight gain appears to be greater than the sum of the additional fetuses and supportive tissue. In general, the greater the weight gain, the greater the birth weight. Unfortunately, there is insufficient information to create specific ranges of weight gain for women expecting twins.
How Quickly Should The Weight Be Gained?
It is not yet clear as to the optimum rate of weight gain for favourable pregnancy, or how this rate varies between trimesters. Weight gain in the first Trimester is usually low and this generally increases smoothly throughout the second and third trimesters. For women of normal prepregnancy weight, gains of around one pound per week are recommended for the 2nd and 3rd Trimesters. Overweight and underweight women will need to vary their intake accordingly to achieve full-term weight goals in line with this figure. In the case of obese women, the situation will have to be dealt with on an individual basis. Smooth weight increases usually reflect a normal gain of lean and fat tissue. Unusually high weight gains can usually be attributed to water retention. This, along with generalised edema and increased blood pressure, may signal pre-eclampsia or pregnancy-induced hypertension.
What Should Your Calorie Intake Levels Be?
Currently, it is believed that caloric intake should exceed prepregnancy levels by around 200-300 calories per day. The amount of caloric intake is largely governed by body size and physical activity, not by gestational weight gain. Although the need for extra calories during pregnancy is not great, restriction of intake can lead to limited weight gain and excessive intake can lead to excess fat deposits. Regular prenatal care including monitoring of weight should identify any unusual weight changes. Any deviation from the prescribed weight gain pattern should be investigated to see if it is related to changes in physical activity or food intake. It is for this reason that the weight gain guidelines are useful, as they provide a means of monitoring and help to detect abnormalities.
Assessment of diet in early pregnancy is essential for every woman. Individual eating patterns can be identified by way of food history or a questionnaire. Added questions about special dietary requirements can identify possible deficiencies. The importance of a balanced diet cannot be sufficiently stressed, listed below are recommended daily amounts from the Food Pyramid Guide Groups.
Food Pyramid Guide Groups
Pregnant or Lactating Women
7 - 11 Servings
4 - 5 Servings
3 - 4 Servings
Meat / Meat Alternatives
Milk / Milk Products
3 - 4 Servings
These groups essentially provide all of the nutrients recommended for pregnancy with the possible exception of Iron for which supplements are an option. Details on this can be found below. Special attention should also be paid to adequate fluid and fiber intake to alleviate constipation. Even with a balanced diet of nutritious food, it is generally necessary to supplement intake with a prenatal supplement to ensure thorough intake of all nutrients.
Important Nutritional Supplements
Calcium absorption is apparently enhanced during pregnancy. Due to this, it is not necessary to increase calcium intake over normal levels when pregnant. The RDA is 1300mg for teenagers and 1000mg for adults. This requirement can be met with 3 - 4 servings of milk and dairy foods daily. Some green vegetables, canned fish and enriched grain products also provide calcium.
The western diet is typically full of protein. Fish, milk, meat, poultry and vegetables are excellent sources and will also provide other nutrients such as Iron, Zinc, Calcium and Vitamin D. These foods should be included in the diet to meet the RDA for protein (60g). This figure is between 10 and 15g higher than that for women who are not pregnant. Protein powders should be discouraged.
A folate deficiency in pregnant women in the western world is rare. However, because folate deficiency has been linked to fetal neural tube defects, it is now recommended that all women of child bearing age consume at least 400 micrograms of folate per day. (This is a typical amount found in mineral / vitamin supplements.) Folate can also be found in fruit and green vegetables.
This is the only nutrient for which recommendations cannot be met solely by dietary intake. During the 2nd and 3rd trimesters, the average pregnant woman needs to consume an extra 3mg of ferrous iron over and above the normal daily dietary intake. A low dose Iron Supplement (30mg) poses no threat to mother or baby, is efficiently absorbed and decreases the intestinal problems often associated with higher doses. Iron is included in Prenatal Supplements.
In certain situations it may be necessary to take selective supplements from the second trimester onwards. These include dietary practices which restrict or inhibit the normal daily intake of various nutrients. For example, complete vegetarians may require Vitamin D or B12 supplements. High-risk pregnancies or other conditions may create a need for extra supplementation or cause undesirable changes in food and nutrient intake. For example, alcohol & drug users and smokers need a multiple vitamin/mineral supplement. In the case of anaemia, it may be necessary to supplement therapeutic doses of iron (more than 30mg/day) with Zinc and Copper to ensure complete absorption.
What to Avoid?
Although the evidence to suggest that caffeine is harmful during pregnancy is inconclusive, it seems sensible to limit caffeine intake where possible. There is insufficient data to suggest a supplement for women who continue to consume caffeine during pregnancy. In order to avoid Vitamin A toxicity (especially in the first trimester), supplementation with Vitamin A is not recommended unless a deficiency is clearly evident. Carotene, found in dark green and yellow or orange fruits is a good source of Vitamin A.