James Morton, RD, CSSD
Nutrition & Dietetics Reviewer
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James Morton, RD, CSSD
Nutrition & Dietetics Reviewer
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Published: February 3, 2026 • 14 min read
Pregnancy nutrition advice is a minefield. Some of it is evidence-based. A lot of it is cultural tradition dressed up as medical guidance. And the food restriction lists have grown so long that many pregnant women feel anxious eating anything at all.
I want to cut through this and present what the major medical organizations (ACOG, IOM, WHO) actually recommend, what the research supports, and where common advice goes beyond what the data warrants. This guide is organized by trimester because nutritional needs genuinely change as pregnancy progresses.
Important disclaimer: This article is educational. Your OB-GYN or midwife knows your specific medical history and should be your primary source of nutrition guidance during pregnancy. Nothing here replaces that relationship.
The American College of Obstetricians and Gynecologists (ACOG) provides clear guidelines on additional calorie needs during pregnancy:
I want to emphasize how small these increases are, because the "eating for two" myth persists and causes real harm. Excessive weight gain during pregnancy increases the risk of gestational diabetes, preeclampsia, C-section delivery, and postpartum weight retention. Goldstein et al. published a 2017 meta-analysis in JAMA showing that excessive gestational weight gain affected nearly half of pregnant women and was associated with increased risk of large-for-gestational-age babies, C-section, and postpartum weight retention.
Our pregnancy weight gain calculator can help you track whether your weight gain is within the recommended range for your pre-pregnancy BMI.
The Institute of Medicine (IOM) published updated weight gain guidelines in 2009. These remain the standard used by ACOG and most healthcare providers:
These ranges are population-level recommendations and have limitations. They were derived primarily from studies of white women in the United States and may not be equally applicable across all populations. Several researchers have suggested the ranges for obese women may be too generous, and there is growing evidence that women with Class III obesity (BMI 40+) may benefit from gaining less than 11 pounds. Discuss your specific targets with your provider.
If you do not know your pre-pregnancy BMI, our BMI calculator can help you calculate it based on your height and pre-pregnancy weight.
Prenatal vitamins are important, but they are not a complete solution. Many commonly available prenatals are missing key nutrients or provide inadequate amounts. Here is what the evidence actually says about each one.
Folate has the longest track record of any nutrient in prenatal care. It is essential for neural tube development, and supplementation dramatically reduces the risk of spina bifida and anencephaly. The CDC recommends 400 mcg of folic acid daily starting at least one month before conception and continuing through the first 12 weeks.
Women with a previous neural tube defect pregnancy or those on certain medications (antiepileptics, methotrexate) may need 4,000 mcg (4 mg) daily. The evidence for folate supplementation in preventing neural tube defects is about as strong as evidence gets in nutrition science. A 1991 MRC Vitamin Study Research Group trial in the Lancet showed a 72% reduction in neural tube defect recurrence with folic acid supplementation.
Blood volume increases by about 45% during pregnancy, and the body needs significantly more iron to support this expansion and fetal development. The recommended intake increases from 18 mg/day to 27 mg/day. Iron deficiency anemia during pregnancy is associated with preterm birth and low birth weight.
Here is the practical challenge: iron supplements cause constipation and nausea in many women, particularly during the first trimester when nausea is already a problem. Taking iron with vitamin C increases absorption and allows a lower effective dose. Taking it at night or with food (though this reduces absorption somewhat) can reduce stomach upset. If you cannot tolerate oral iron, discuss alternatives like iron bisglycinate or IV iron with your provider.
DHA is an omega-3 fatty acid that the fetal brain and eyes need in large quantities. The brain is approximately 60% fat by dry weight, and DHA is the predominant structural fatty acid. The International Society for the Study of Fatty Acids and Lipids recommends 200-300 mg of DHA daily during pregnancy.
Many prenatal vitamins either skip DHA entirely or include a trivially small amount. Check the label. If your prenatal does not contain at least 200 mg of DHA, consider a separate DHA supplement or eat 2-3 servings of low-mercury fatty fish per week (salmon, sardines, herring). Fish oil supplements are generally considered safe during pregnancy, though the specific brand matters because of potential mercury contamination in lower-quality products.
Choline gets almost no attention in prenatal care, which is a problem. It is essential for brain development, particularly the hippocampus (memory center), and for preventing neural tube defects in conjunction with folate. The AI (Adequate Intake) for pregnant women is 450 mg/day.
A 2018 randomized controlled trial by Caudill et al. published in the FASEB Journal found that maternal choline intake of 930 mg/day (double the AI) improved infant information processing speed compared to intake at the AI level. This suggests the current recommendations may actually be too low.
Most prenatal vitamins contain little to no choline. The best food sources are egg yolks (147 mg per yolk), beef liver, chicken, fish, and soybeans. If you eat 2 eggs daily, you are getting roughly 300 mg. The rest should come from other dietary sources or a supplement.
Vitamin D deficiency during pregnancy is associated with increased risk of preeclampsia, gestational diabetes, and preterm birth. A 2017 meta-analysis by Palacios et al. in the Cochrane Database of Systematic Reviews found that vitamin D supplementation probably reduced the risk of preeclampsia, gestational diabetes, and low birth weight.
ACOG recommends 600 IU daily during pregnancy, but many researchers (including Hollis and Wagner, who conducted large RCTs in pregnant women) argue that 4,000 IU daily is safe and more effective at achieving adequate blood levels. The Endocrine Society recommends at least 1,500-2,000 IU daily for pregnant women. Ask your provider to check your 25(OH)D level and supplement accordingly.
Iodine tends to fly under the radar, but the fetus needs it for thyroid development and brain growth. The recommended intake during pregnancy is 220 mcg/day (up from 150 mcg for non-pregnant adults). WHO considers iodine deficiency the most common preventable cause of intellectual disability worldwide. Many prenatal vitamins now include iodine, but check your label. If it is not there, iodized salt (about 95 mcg per half teaspoon) and dairy products are good dietary sources.
Nausea and vomiting affect 70-80% of pregnant women, typically peaking between weeks 8 and 12. For most women, it resolves by week 16. For 1-3% of women, it becomes hyperemesis gravidarum (severe, persistent vomiting requiring medical treatment).
Here is what the evidence supports for managing standard pregnancy nausea:
One important reassurance: mild to moderate nausea during the first trimester, even if it limits food intake, is not harmful to the baby. The embryo's calorie needs at this stage are minimal (remember: no extra calories needed in the first trimester). Focus on staying hydrated and eating whatever you can tolerate. Nutritional perfection is not the goal during weeks 6-12. Survival is.
Gestational diabetes mellitus (GDM) affects 6-9% of pregnancies in the United States. It typically develops during the second trimester as placental hormones create increasing insulin resistance. Screening usually happens between weeks 24 and 28 with a glucose challenge test.
If diagnosed with GDM, dietary management is the first-line treatment. The goal is to keep blood glucose within target ranges while still meeting nutritional needs. The general approach includes:
GDM usually resolves after delivery, but it increases long-term risk of developing type 2 diabetes by about 50% within 10 years. Continued attention to diet and exercise postpartum matters.
The list of "foods to avoid during pregnancy" has expanded far beyond what the evidence supports, creating unnecessary anxiety. Let me separate the evidence-based restrictions from the overcautious ones.
Exercise during pregnancy is not just safe for most women, it is actively beneficial. ACOG's 2020 Committee Opinion (Number 804) recommends that pregnant women with uncomplicated pregnancies get at least 150 minutes of moderate-intensity aerobic activity per week.
The research on this is clear:
Walking, swimming, stationary cycling, low-impact aerobics, yoga (modified), and strength training with moderate loads are all considered safe throughout pregnancy. Women who were running, weightlifting, or doing CrossFit before pregnancy can generally continue with modifications (discussed with their provider).
Contact sports with fall risk (soccer, basketball, horseback riding), scuba diving (risk of decompression sickness to the fetus), activities at altitude above 6,000 feet (for those not already acclimated), and hot yoga or exercise in extreme heat (hyperthermia risk, especially in the first trimester).
After the first trimester, avoid exercises performed flat on your back for extended periods, as the weight of the uterus can compress the inferior vena cava and reduce blood flow. Incline positions are fine.
Our calculators can help you track key metrics throughout your pregnancy: