Pregnancy nutrition
Written by: Aoun Rita
April, 2020
Table of Contents
Nutritional needs during pregnancy. 4
Energy Expenditure during Pregnancy. 4
Gestational weight gain and pregnancy outcome. 8
Excessive gestational weight gain. 9
Inadequate gestational weight gain. 9
Physical activity during pregnancy. 9
Nutrition during lactation. 13
During pregnancy and breastfeeding lifestyle and dietary habits are critical determinants of health of both mother and fetus. Starting from the preconceptional period, maternal nutrition is crucial to ensure the maternal well-being and pregnancy outcomes, as well as ensuring long term health of the offspring. In fact, current scientific literature highlights that the first 1000 days of life starting from conception plays an important role in the prevention of non-communicable diseases (NCDs) in adulthood (1). Moreover, certain maternal conditions such as obesity prior to pregnancy and excessive weight gain during pregnancy are associated with adverse pregnancy outcomes and influences negatively child’s health in its early life (2). Breastfeeding, “the gold standard” of infant feeding has also a critical role in infant health outcome. It is well known that it saves and improves the quality of life (3). Thus, optimizing nutrition prior and during pregnancy and promoting breastfeeding are critical interventions to reduce chronic disease risk later in life.
Appropriate weight gain and consumption of an adequate healthy diet are two key components of a health-promoting lifestyle during pregnancy. The optimal supply of nutrients and oxygen from the mother to the developing fetus is required to achieve appropriate fetal growth and development. During pregnancy, the total energy needs are increased because of the increased maternal metabolism, blood volume and red cell mass expansion by 50%, and the delivery of nutrients to the fetus (4).
A total of 80,000 kcal is needed to support a full-term pregnancy to account for increased maternal metabolism and fetal growth. Thus, caloric intake should increase by about 300 kcal/day during pregnancy (the mean pregnancy duration is 250 days) (5). The Institute of Medicine 2002, advise no additional calories for the first trimester, addition of 340 Kcal/day for the second trimester and 452 kcal/day in the third trimester. However, there are factors that affect caloric requirements such as woman’s age, preconception BMI, and activity level. Therefore, caloric intake must be individualized.
To ensure the full-term delivery of a healthy newborn, adequate dietary protein is crucial during pregnancy. Protein needs increases progressively throughout pregnancy to maintain maternal tissues and fetal growth, particularly during the third trimester. Thus, guidelines agree on increasing protein requirements during pregnancy, especially during the second and third trimester to ensure the extra 21 grams needed for maternal tissues and fetal growth (6). Protein recommendation for non-pregnant women is 0.8g of protein/kg/day. However, according to the 2002 DRI for pregnant women, the amount of protein recommended is 1.1g of protein/kg/day, or an extra 25 g/day to meet the requirements of pregnancy. Insufficient energy and protein intake during pregnancy may be associated with preterm birth and have several adverse effects on both mother and fetus (7).
Glucose is the main energy substrate for fetal rapid growth and development and is transmitted in a regular from mother to fetus (8). It should be available to the fetus at all times to ensure his normal growth. The recommended daily allowance (RDA) for pregnant women is 175 g/day whereas the RDA for non-pregnant women is 130 g/day. Moreover, adequate fiber supply is important during pregnancy; it helps in reducing constipation which is a common side effect of pregnancy. The DRI for fiber during pregnancy is 28 g/ day. Fiber rich foods include whole-grain breads and cereals, fresh fruits and vegetables and legumes.
Furthermore, during pregnancy adequate carbohydrate intake is crucial for an active pregnant woman. Indeed, pregnant women use carbohydrates at a higher rate during exercise than do non-pregnant women (9). Studies have shown that there is preferential use of carbohydrates during anaerobic exercises such as non-weight bearing exercise during pregnancy (10).
During pregnancy, the quality of fats is more important than their total quantity. In fact, PUFA are of utmost importance; they play a critical role in fetal development and infant growth. Eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA) are typically referred to as n-3 long-chain PUFA. Many systematic reviews revealed a positive impact of maternal intake and status of n-3 long-chain PUFA during pregnancy and lactation on maternal, infant, and child health (11) (12) (13).
Of these n-3 long-chain PUFA, DHA is of greatest importance. Indeed, it is the main PUFA in the human brain and retinal rods and, thus, is critical for optimal fetal neurodevelopment. Several literatures supported the benefits of DHA for the fetus and overall infant health and maternal health (14) (15).
DHA and EPA can only be obtained from dietary sources. The richest sources of these fatty acids are seafood and fish oil supplements. Vegetable oils and flax seed oil do not contain directly EPA and DHA, they contain ALA that needs to be converted to EPA and DHA to become biologically active. According to US Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) pregnant woman should consume 2 to 3 serving of seafood per week to optimize pregnancy outcomes (16). The 2015–2020 Dietary Guidelines for Americans states that pregnant or lactating women should consume 8–12 ounces of low mercury fish every week, such as salmon, sardines, and trout.
Micronutrient requirements during pregnancy increase more than those of macronutrients. They play a crucial physiological role in pregnancy. Thus, insufficient intakes influence fetal development and can have significant consequences for the mother. A pregnant woman should make sure to get enough of each vitamin/mineral and not to exceed the daily maximum for each vitamin/mineral. Table 1 shows the RDA for vitamins and minerals during pregnancy.
|
Nutrient |
Non-Pregnant |
Pregnant* |
Lactation* |
|
Vitamin A (μg/d) |
700 |
770 |
1300 |
|
Vitamin D (μg/d) |
5 |
15 |
15 |
|
Vitamin E (mg/d) |
15 |
15 |
19 |
|
Vitamin K (μg/d) |
90 |
90 |
90 |
|
Folate (μg/d) |
400 |
600 |
500 |
|
Niacin (mg/d) |
14 |
18 |
17 |
|
Riboflavin (mg/d) |
1.1 |
1.4 |
1.6 |
|
Thiamin (mg/d) |
1.1 |
1.4 |
1.4 |
|
Vitamin B6 (mg/d) |
1.3 |
1.9 |
2 |
|
Vitamin B12 (μg/d) |
2.4 |
2.6 |
2.8 |
|
Vitamin C (mg/d) |
75 |
85 |
120 |
|
Calcium (mg/d) |
1,000 |
1,000 |
1,000 |
|
Iron (mg/d) |
18 |
27 |
9 |
|
Phosphorus (mg/d) |
700 |
700 |
700 |
|
Selenium (μg/d) |
55 |
60 |
70 |
|
Zinc (mg/d) |
8 |
11 |
12 |
*Applies to women >18 years old
Table: Recommended daily dietary allowances for pregnant and lactating women. Data from Otten JJ, Pitzi Hellwig J, Meyers LD, Editors. Dietary reference intakes. The essential guide to nutrient requirements. Washington, DC: National Academies Press; 2006.
Folate requirements are greater in pregnancy than in the non-pregnant state in order to support rapid cell growth in the fetus and placental development. Women should be advocated to maintain a healthy folate-rich diet. Rich sources of folate include dark-green leafy vegetables, orange juice, legumes and fortified foods such as bread and cereals. Dietary supplementation with folate for women planning a pregnancy or recently pregnant is recommended. In fact, folic acid supplementation taken prior to conception has long been known to decrease the risk of neural tube defects (NTDs) in the newborn (17). According to the U. S. Public Health Service and CDC, women of childbearing age are recommended to take 400 micrograms of folic acid daily (18).
During pregnancy, iron requirement gradually increases until the third month, in parallel with the accumulation in fetal tissues. Insufficient intakes during pregnancy may affect growth and development of the fetus, and are associated with increased risk of preterm delivery, low birth weight and post-partum hemorrhages (20). Moreover, recent studies presented an association between inadequate iron intakes during pregnancy and increased cardiovascular risk for the offspring later in adult life (21). According to the Center for Disease Control and Prevention and the WHO it is advised that iron intake for all pregnant women is 27 mg per day. Iron supplementation is often recommended to meet the iron needs of both mother and fetus, and to optimize pregnancy outcomes (19) (20).
During pregnancy there is no need for additional calcium intake since it’s intestinal absorption increases (22). According to World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO), pregnant women are recommended to consume 1200 mg/day of calcium (23). Several adverse effects in both the mother and the fetus occur in case of inadequate calcium consumption during pregnancy, such as: Osteopenia, poor fetal mineralization, muscle cramping, low birth weight and delayed fetal growth (24). Adequate calcium intake through calcium-rich foods should be promoted. However, when calcium intake is low, calcium supplementation is recommended. Numerous studies have suggested that calcium supplementation during pregnancy decreases the risk of pre-eclampsia, especially among pregnant woman with high risk of hypertension (24).
There are notably two key parameters that influences pregnancy outcome and offspring birth weight: pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) (25). In fact, these two are known to be predictors of the maternal nutritional status. Healthier offspring and maternal outcomes were shown with adequate pre-pregnancy weight and gestational weight gain (26).
The essential weight gain during pregnancy is around 8 kg which accounts for the fetus, the placenta, amniotic fluid volume, breast tissues and uterus, interstitial fluid and blood volume. Gradually, maternal adipose tissue increase serving as an energy reserve for pregnancy and lactation. If weight gain is less than 8Kgs this indicates that existing maternal adipose and protein stores will be catabolized in order to support the pregnancy. In 2009, the Institute of Medicine (IOM) has modified the guidelines concerning gestational weight gain (Table 2). The last recommendations of pregnancy weight gain according to different BMI categories has been released in 1990.
|
Pre-pregnancy BMI |
Total weight gain at term |
Rate of weight gain in the 2nd and 3rd trimester; Mean (range) |
|
Underweight (<18.5 kg/m2) |
12.5-18 kg 28-40 lbs. |
0.51 (0.44-0.58) kg/week 1 (1-1.3) lbs./week |
|
Normal weight (18.5-24.9 kg/m2) |
11.5-16 kg 25-35 lbs. |
0.42 (0.35-0.50) kg/week 1 (0.8-1) lbs./week |
|
Overweight (25.0-29.9 kg/m2) |
7-11.5 kg 15-25 lbs. |
0.28 (0.23-0.33) kg/week 0.6 (0.5-0.7) lbs./week |
|
Obesity |
5-9 kg 11-20 lbs. |
0.22 (0.17-0.27) kg/week 0.5 (0.4-0.6) lbs./week |
Table: Gestational weight gain recommendations Data from Institute of Medicine. Weight gain during pregnancy: reexamining the guidelines. Washington, DC: Institute of Medicine; 2009.
Excessive gestational weight gain (GWG) is a public health concern in both developed and developing countries. Women who gain weight in excess of current recommendations during pregnancy have a higher risk to develop pregnancy complications such as gestational diabetes mellitus (27) and also increases their likelihood to remain overweight postpartum. Moreover, they increase the risk of delivering a baby by caesarean section (28) and put their child at a greater risk of childhood overweight or obesity (29).
Deficiencies of calories and macronutrients during pregnancy is just as harmful as their excess.
Low gestational weight gain is considered to be an independent predictor of negative pregnancy outcomes. In fact, studies have found that it is positively associated with preterm birth and increased risk of low birth weight (30) (31).
Intensive interventions in diet and physical activity may be needed to inhibit excessive weight gain during pregnancy specially in overweight and obese women. In fact, women who are physically active during their pregnancies have less risk of excessive gestational weight gain. The US Department of Health and Human Services Physical Activity Guidelines recommend that healthy pregnant women get at least 150 minutes of moderate intensity aerobic activity per week (32).
Numerous studies investigate the association between physical activity and gestational weight gain. These studies have consistently demonstrated that:
Furthermore, Choi et al, in their 2013 meta-analysis of 7 trials (N=721), focused on trials of different physical activity interventions that varied in terms of frequency, duration and supervision among overweight/obese women (37). A notable reduction in gestational weight gain have been showed in the meta-analysis. The greatest effect was observed when supervised physical activity and dietary intervention were combined together (37).
In 2012, Jiang et al. have conducted a cohort study on Chinese pregnant women to investigate the relationship between physical activity during pregnancy and gestational weight gain (38). A pedometer was used to measure physical activity levels of pregnant women in the 2nd and 3rd trimester. According to the pedometer, pregnant women were divided into 4 different groups: Sedentary, Low Active, Somewhat Active and Active. Data were collected from the 2nd trimester to delivery. Table 3 presents the steps taken by pregnant women based on their category. The results of the study showed a significant association between physical activity and gestational weight gain. Table 4 shows the weight gain of pregnant women based on their physical activity. Indeed, in the last two trimesters, the sedentary group had 1.45 kg more GWG, than the active group (38).
Table 3: Steps taken by pregnant women based on their physical activity.
Jiang, H., Qian, X., Li, M., Lynn, H., Fan, Y., Jiang, H., … He, G. (2012). Can physical activity reduce excessive gestational weight gain? Findings from a Chinese urban pregnant women cohort study. The International Journal of Behavioral Nutrition and Physical Activity, 9, 12
Table 4: Weight gain of pregnant women based on their physical activity.
Jiang, H., Qian, X., Li, M., Lynn, H., Fan, Y., Jiang, H., … He, G. (2012). Can physical activity reduce excessive gestational weight gain? Findings from a Chinese urban pregnant women cohort study. The International Journal of Behavioral Nutrition and Physical Activity, 9, 12
Breast milk is considered the “gold standard” for infant feeding. The World Health Organization, the American Academy of Pediatrics, the Academy of Breastfeeding Medicine and the American Congress of Obstetricians and Gynecologists all support this statement. According to the American Academy of Pediatrics, exclusive breastfeeding should be recommended for the first 6 months and breastfeeding at least through the first year of life (39).
Mother’s energy needs and nutritional requirements increases during lactation to ensure milk production. In fact, the energy content of the milk is 67 Kcal/100 mL (40). Thus, during the first 6 months’ breastfeeding women requires 500 additional Kcal/day (41). lactating women usually lose 0.5 to 1 Kg/month (42).
During lactation, carbohydrates are important to support adequate energy level and to provide enough calories in the diet for milk production. Thus, the RDA of breastfeeding women for carbohydrate is 210 g/day.
As for protein intake during exclusive breastfeeding, it should be increased by 21 g/day in the first semester and 14 g/day later, if breastfeeding is continued throughout the year (43).
The American Academy of Pediatrics advices breastfeeding women to consume one to two servings of fish per week to assure a sufficient amount of DHA in breast milk (44). Indeed, the DHA is critical in the first months for the newborn psychomotor neurodevelopment. However, the overall intake of fat during breastfeeding is not necessary to change (45).
Numerous studies have shown a strong association between lifestyle and dietary habits during pregnancy and lactation and the health of the women and her offspring. Adequate and balanced diet prior to conception till delivery is critical for maternal well-being and optimal pregnancy outcomes. However, in both developing and non-developing countries there is a high risk of malnutrition during pregnancy and lactation; thus, nutrition counseling and lifestyle modification should be encouraged for women of childbearing age.
Finally, effective interventions that target lifestyle modification, health behaviors and dietary intake are needed to improve a woman’s health status and help her in meeting the gestational weight gain goals to optimize pregnancy outcomes.
Aoun Rita
April 15,2020
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