Nutrition Needs for Clients who are Pregnant or Nursing

by Natalie Digate Muth, MD, MPH, RD on May 01, 2007

Everything expectant moms need to know about what to eat and what to avoid during pregnancy and when breastfeeding.

In a typical mom-to-be, the news of a pregnancy is met with excitement, anxiety and a frantic desire to learn everything needed to ensure that her child is born healthy. Whether that newly pregnant woman is yourself, a client, a friend, a workout buddy or a spouse, as a fitness professional, you can serve as a ready source of general information on how she should eat for optimal growth and development of her baby.

This article will examine the most widely accepted, research-based nutrition recommendations for women during pregnancy and lactation. To provide a foundation, the article will also discuss the hormonal and physiological changes that take place during the course of a typical 40-week pregnancy. This foundation will provide the context to explain the unique nutrition needs of women during this exciting new phase of their lives.

Physiological Changes During Pregnancy

From the moment of conception, a pregnant woman’s body begins to adapt to meet the demands of the developing embryo and to create the most favorable environment for a growing baby. In fact, pregnancy affects the function of nearly every organ system within the mother’s body.

The cardiovascular system responds by working more efficiently and pumping out more blood per beat to better supply tissues with oxygen. Blood volume also increases drastically during pregnancy. This, in turn, causes the normal phenomenon of pregnancy-induced anemia, a condition in which the increase in red blood cell production is not as rapid or complete as the increase in blood volume. The rapid rise in blood volume that usually occurs near the end of the first trimester is also responsible for the lightheadedness and dizziness that some women may experience. Blood levels return to normal near the end of the second trimester (Hacker, Moore & Gambone 2004; Worthington-Roberts & Williams 1997).

Pregnant women even breathe more deeply and have a slightly increased respiratory rate; this is an attempt by the maternal body to decrease carbon dioxide levels in the developing fetus and to provide the mom-to-be with sufficient oxygen to add tissue mass to the uterus and breasts.

The kidneys also must work harder during pregnancy, to get rid of both fetal and maternal waste. This is complicated by the fact that the growing uterus is located in the perfect position to apply extra pressure on the bladder; therefore, it’s no wonder that frequent bathroom breaks become an annoyance for many women during the later stages of pregnancy.

The gastrointestinal system could win an award for the most noticeable pregnancy-induced changes. These changes may include many or all of the following:

  • an increase in appetite
  • nausea and vomiting
  • decreased motility and slowing of digestion
  • alterations in the sense of taste
  • increased nutrient absorption
  • heartburn-causing acid reflux
  • constipation (Hacker, Moore & Gambone 2004; Worthington-Roberts & Williams 1997).

Hormonal & Metabolic Changes

Many of the physiological changes of pregnancy are due to a hormonal influx of more than 30 different hormones that are secreted throughout the gestation period (Worthington-Roberts & Williams 1997). At conception, the embryo begins producing human chorionic gonadotropin, or hCG. This hormone is thought to be largely responsible for the early pregnancy changes, such as a missed period, morning sickness and tender breasts.

Near the end of the first trimester, the placenta in the mother’s body begins taking over hormone production from the embryo. Progesterone, which is at its highest levels in the early months of pregnancy, causes relaxation of smooth muscles and helps stretch the uterus; it also causes many of the changes to the gastrointestinal system and induces maternal fat deposition.

Estrogen, which rises sharply near the end of pregnancy, promotes the growth and function of the uterus and is also responsible for the fluid retention and swelling often experienced in the third trimester. Hormonal changes also help maintain nutrient flow to the fetus and promote mammary development, which later becomes important for breastfeeding (Hacker, Moore & Gambone 2004; Worthington-Roberts & Williams 1997).

Beginning around the fourth month of pregnancy, maternal metabolism increases by about 15%, rising to 20% by the time of delivery and leading to greater hunger and higher caloric intake (Hacker, Moore & Gambone 2004). This metabolic increase is essential during pregnancy to meet all of the changing needs of the various organ systems and to provide adequate fuel and nutrition to the developing fetus.

Metabolism returns to nonpregnant levels about 1 week after the baby’s delivery if the new mom does not breastfeed (Hacker, Moore & Gambone 2004; Worthington-Roberts & Williams 1997). If the woman decides to breastfeed, metabolic levels remain elevated, reflecting the extra energy needed to produce nutrient-dense milk.

Maternal Weight Gain & Caloric Needs

The first question that many newly pregnant women ask is “How much weight should I gain?” In general, the American College of Obstetrics and Gynecology (ACOG) recommends that women who are underweight (body mass index [BMI]<19) gain about 28–40 pounds (ACOG 2004; Hacker, Moore & Gambone 2004). Those women who are normal weight are advised to gain in the range of 25–35 pounds, whereas women who are overweight (BMI >25) should gain only 15–25 pounds (ACOG 2004; Hacker, Moore & Gambone 2004). Too little weight gain often leads to low birth weight, while too much is associated with a condition known as macrosomia, or excessive birth weight (greater than about 9 pounds) (Hacker, Moore & Gambone 2004).

Specifically, when it comes to total weight gain during pregnancy, keep in mind that the fetus weighs about 7–8 pounds, the placenta and amniotic fluid 3–4 pounds, tissue fluid 5–6 pounds, maternal blood 3–4 pounds, enlargement of the uterus 2–3 pounds and maternal fat stores 5–8 pounds (Worthington-Roberts & Williams 1997). An obstetrician can provide further information about healthful weight gain, as well as an individualized assessment of each woman’s situation.

So how many extra calories does a pregnant woman need for the growing baby and to gain the appropriate amount of weight delineated above? Energy needs during pregnancy increase by about 300 calories per day throughout the second and third trimesters. That’s equivalent to an extra glass of milk and a slice of peanut butter toast per day. So while it’s often said that a pregnant woman is “eating for two,” the truth is that her energy needs really increase by a mere 12%, assuming that her needs prior to the pregnancy were within the 2,200 calories per day recommended for young, active women.

The bottom line is that it is less about increasing the total number of calories during pregnancy than it is about increasing the quality and nutrient density of the extra calories. While the occasional midnight binge of ice cream and pickles is not a problem for most women, a balanced and healthy diet will ensure an adequate intake of nutrients and minerals, which are vital for a healthy pregnancy and a growing baby.

General Nutrition Considerations

Pregnant women, especially those with unique nutrition needs, are encouraged to see a registered dietitian (RD) or other qualified professional for an individualized nutrition plan. However, fitness professionals are often asked questions by their pregnant and nursing clients. You can play a role in helping these clients eat healthily by providing them with the latest research-based news about pregnancy and diet. But you do need to stay within your scope of practice and avoid making recommendations about specific food plans or diets.

A healthy nutrition plan in pregnancy begins with eating small, frequent meals. Those traditional “three square meals a day” are best replaced by five small meals—breakfast, lunch, an afternoon snack, dinner and a bedtime snack. Pregnant women should avoid fasting (>13 hours) and should never skip breakfast, as doing so can increase the risk of a dangerous condition called ketosis, which is an increased acidity of the blood that can increase the risk of preterm delivery. Most nutrition experts caution that it is never healthy to diet during pregnancy (Hacker, Moore & Gambone 2004).

Instead, pregnant women are encouraged to eat an abundance of fruits, vegetables, whole grains and high-calcium foods during the entire gestation period. Other nutrition recommendations are more specific to the exact stage of fetal growth and development, which by convention is divided into pregnancy trimesters and postpartum lactation.

The First Trimester (Weeks 0–12)

Because the body is bombarded with hormonal changes in early pregnancy, at least 70% of moms-to-be experience nausea, vomiting, fatigue, stress and/or other discomforts in the first trimester (ACOG 2004).

For the baby, the first trimester is the most critical period in terms of its future health. The first 3 months mark the time of implantation, organ development and rapid growth. It is when good nutrition is paramount but challenging, especially for women plagued by relentless morning sickness. Weight gain may be nonexistent or up to about 1 pound per month during the first trimester (Hacker, Moore & Gambone 2004).

Obviously, maintaining optimal nutrition through healthful food choices, such as fruits, vegetables, dairy products, whole grains and lean protein, is ideal. But another important task for any future mother is remembering to take a prenatal vitamin every day.

Among a variety of other nutrients, a prenatal vitamin should contain at least 400 micrograms (mcg) of folic acid. Adequate intake of folic acid prevents about 60% of neural-tube defects, such as spina bifida and anencephaly, two devastating neurological abnormalities that result from an improperly formed spinal cord (CDC 2005; MRC Vitamin Study Research Group 1991). Folic acid prevents these kinds of defects if supplementation is initiated in the first several weeks of pregnancy, since the neural tube closes about 3–4 weeks after conception. However, because women often do not know they are pregnant in the first few weeks, public-health officials encourage all women of childbearing age to take a supplement that contains at least 400 mcg of folic acid. And while generous consumption of dark-green, leafy vegetables; fortified cereals; and fruits like oranges and strawberries may provide enough folate, taking a daily prenatal vitamin eliminates the guesswork and assures sufficient intake.

Although folic acid can decrease the risk of severe neurological defects, the Centers for Disease Control and Prevention estimates that only 33% of women of childbearing age take the supplement, and a mere 7% recognize the importance of folic acid prior to becoming pregnant (CDC 2005). It is also vital that vegans (i.e., vegetarians who exclude all animal products) take a vitamin B12 supplement during pregnancy, because a deficiency in this vitamin can also contribute to neural-tube defects.

Iron is another important component of any prenatal vitamin. The CDC recommends that all pregnant women take a daily supplement containing 30 milligrams (mg) of iron, since many women have difficulty maintaining iron stores during pregnancy (CDC 1998). Although research has not established that all pregnant women need an iron supplement, supplementation within recommended doses is not associated with health risks and it helps women maintain iron stores while pregnant. Excellent food sources of iron include lean red meat, fish, poultry, beans, dried fruits and iron-fortified cereals. It should also be noted that vitamin C increases iron absorption, meaning that iron-rich foods (or an iron-fortified supplement) are best consumed with orange juice or tomato juice or with other foods that are rich in vitamin C.

Calcium is another important nutrient throughout pregnancy. The developing fetus builds its bones through available calcium in the maternal bloodstream. In the fetus, calcium is also used to conduct nerve impulses and build strong muscles and a strong heart. As with other nutrients, the baby gets access to circulating calcium first. If calcium intake is not adequate, maternal bone strength is at risk. Because calcium absorption increases during pregnancy, the calcium needs of pregnant women are similar to those of nonpregnant women: about 1,000–1,200 mg per day, equivalent to about 3–4 glasses of milk per day (Richie & King 2000). Some experts say that adequate calcium intake may also help prevent pregnancy-induced high blood pressure and pre-eclampsia (Ritchie & King 2000). Although calcium is best gleaned through food sources (e.g., dairy products, fortified foods/juices, cooked spinach and broccoli), a calcium supplement can help certain clients meet their nutrition needs during pregnancy. Adequate vitamin D intake is also important for moms-to-be, as it aids in calcium absorption.

Prenatal vitamins provide an abundance of other vitamins and minerals important in early pregnancy. However, vitamins should act more as insurance than as the primary source of nutrition. That’s because, in some cases, it is possible to have too much of a good thing. For instance, consumption of more than 10,000 International Units of vitamin A in early pregnancy can actually cause birth defects (Rothman et al. 1995).

A precaution throughout pregnancy—but especially during the first trimester, when the baby’s organs are developing—is to avoid alcohol consumption. Certainly, many moms-to-be do not know that they are pregnant from the first day of conception and may have had a glass of wine or a couple of beers early in the pregnancy. Most research suggests that this will not cause serious birth defects, since during the first 2 weeks after conception, the fetus will either miscarry or develop normally (Lewanda 2000). However, after 2 weeks, the risks to the fetus increase substantially, depending on the amount of alcohol consumed. Clients should understand that no safe level of alcohol consumption has been established for pregnant women. Alcohol-induced problems, such as mental retardation, learning disabilities and fetal alcohol syndrome and its associated birth defects, are entirely preventable with abstinence. Since it is unknown what amount of alcohol intake can cause fetal damage, health experts advise that alcohol be avoided entirely throughout pregnancy (U.S. Surgeon General 2005; American Academy of Pediatrics 2000).

Caffeine is also a potentially dangerous substance during pregnancy, particularly when consumed in high doses. Caffeine readily crosses the placenta (which develops at the end of the first trimester) and can affect fetal heart rate and breathing. It can also increase the risk of miscarriage, sudden infant death syndrome and low birth weight, according to the American Dietetic Association (ADA 2002), and very high doses may result in congenital anomalies or birth defects (Browne 2006). Although studies have been mostly inconclusive and no one really knows the true risks of caffeine consumption, many experts recommend limiting intake to no more than 300 mg per day—and preferably much less than that (March of Dimes 2007). That’s roughly equivalent to two 8-ounce cups of coffee, three 8-ounce glasses of black tea or five 12-ounce cans of soda per day (March of Dimes 2007). It is especially important to limit caffeine during the first trimester, when the baby’s organs are developing and the risk of miscarriage is highest.

For more nutrition tips see “Foods to Avoid or Limit When Pregnant or Nursing” on page 50.

The Second Trimester (Weeks 13–26)

Sometimes called the “honeymoon” of pregnancy, the second trimester marks the transition from feeling debilitated by morning sickness and decreased appetite to feeling better and developing a somewhat voracious desire for food. Note that while this is true for many women, it is not uncommon for the first-trimester blues to far outlast the crossover from week 12 to week 13.

Now is also a great time for clients to resume their regular exercise program if it was abandoned owing to first-trimester sickness and fatigue. By about week 20, the “pregnant belly” begins to show for most women. Also, the chance of miscarriage, which was 15% during the first trimester, now drops to less than 3% (Hacker, Moore & Gambone 2004).

Second-trimester weight gain averages about 1 pound per week, although this will vary considerably among clients. This is a period of rapid fetal growth, leading to an increase in maternal nutrition needs of about 300 calories per day (Worthington-Roberts & Williams 1997).

Protein is especially important during the second trimester, to help in the development and growth of the fetus’s vital organs. In fact, protein needs increase from about 46 grams (g) before pregnancy to about 71 g throughout pregnancy and lactation (Institute of Medicine 2002).

The second trimester may also be a good time to begin focusing on omega-3 fatty acid intake, either from foods (such as salmon or other fatty fishes) or a fish oil supplement containing docosahexaenoic acid (DHA). Research suggests that fish oils may enhance pregnancy duration and improve the baby’s later cognitive, visual and cardiovascular development (Szajewska, Horvath & Koletzko 2006). A more recent study found that children whose mothers consumed more than three servings of seafood per week during pregnancy had better social behaviors, communication skills and fine-motor development than children whose mothers ate lower amounts of seafood during pregnancy (Hibbeln et al. 2007). However, keep in mind that while seafood may be beneficial to the health of the embryo, it is important that pregnant women limit their intake of the types of fish that tend to be high in mercury (see “Foods to Avoid or Limit When Pregnant or Nursing” on page 50 for details).

Weird food cravings, which some experts feel may signify nutrient deficiencies, can also surface during this time. For example, a meat craving may be the body’s way of signaling that it needs more iron, whereas a desire for nonfood substances, such as dirt and paper, may indicate generalized malnutrition that needs further medical attention. Of course, more typical cravings are for ice cream or fast food. While these “indulgences” are fine in moderation, pregnant women are encouraged to meet their extra caloric needs through healthful foods, while remembering that energy needs do not increase that substantially. Remind your clients that excess calories consumed beyond those truly needed during pregnancy will be readily stored as fat.

The Third Trimester (Weeks 27–40)

The nutritional needs of the fetus are most pronounced during the third trimester. Approximately 50%–70% of the calories required by the fetus are derived from glucose; 20% from protein; and the remainder from fat (Worthington-Roberts & Williams 1997). In order to maximize glucose availability to the fetus, the maternal energy source is primarily fat (Worthington-Roberts & Williams 1997).

During this last trimester, it is especially important to consume carbohydrates regularly throughout the day to provide an adequate supply of glucose to the fetus. Also, women should continue taking a DHA supplement, along with a daily prenatal vitamin. Weight gain should be about 1 pound per week during this period; however, this can vary. By the end of the third trimester, total weight gain should be about 25–35 pounds for most women (Hacker, Moore & Gambone 2004).

Postpartum Nutrition

After the birth of the baby, the new mom is faced with the task of caring for the newborn as well as herself. Breast milk is nature’s perfect nutrition for a newborn, providing the ideal nutrient mix, increasing protection against a variety of infections and building strong bones. Breastfeeding is also linked to deeper bonding between mother and baby, higher IQ in the child and many other benefits (USDHHS 2005).

All new moms who are motivated and capable of breastfeeding are highly encouraged to do so exclusively, not only for the dramatic and significant benefits to the child, but also for the maternal benefits, which include accelerated postpartum weight loss (when combined with a healthy diet and exercise), decreased risk of breast and ovarian cancer, the mother-baby bonding and cost savings (USDHHS 2005). You might want to remind your clients that breastfeeding women expend an additional 500 calories per day, meaning that caloric needs are even higher during lactation than during any trimester of pregnancy (Worthington-Roberts & Williams 1997).

While breastfeeding is great for all involved, some women choose not to nurse, for personal reasons, and others cannot, for medical reasons. Make sure you respect the decisions your clients make, and do not insinuate that they are in any way wrong if they choose to use formula instead.

Now is also an excellent time for clients to permanently adopt the healthful nutrition changes they initiated during pregnancy; for example, eating more fruits, vegetables and whole grains and not smoking. Breastfeeding moms can drink alcohol in moderation but are encouraged not to do so within 3 hours of breastfeeding (La Leche League International 2006). Also, continuing with a DHA supplement and a prenatal vitamin is thought to be beneficial for the breastfeeding newborn.

A Pregnant Pause

Consuming a healthful, nutrient-dense diet throughout pregnancy and while nursing can help set the stage for an optimal birth and postnatal experience. That said, all the recommendations and guidelines women are bombarded with can be overwhelming to moms-to-be.

You can help your expectant clients by sharing information on the benefits of eating healthily within the ranges specified in the government’s food pyramid; being physically active at least 30 minutes most days of the week; taking a prenatal vitamin; and breastfeeding if possible. Perhaps most important, remind them that women have been having healthy babies for thousands of years. Finally, suggest that your pregnant clients relax, take a few deep breaths and enjoy this special time in their lives.


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About the Author

Natalie Digate Muth, MD, MPH, RD

Natalie Digate Muth, MD, MPH, RD IDEA Author/Presenter

Natalie Digate Muth, MD, MPH, RD, is a registered dietitian and a recent graduate of the UNC School of Medicine. She has made several appearances as a nutrition expert on CW's San Diego 6, been quo...