Diet in Pregnancy - Short Note

Introduction

• Creasy & Resnik's Maternal-Fetal Medicine, p. 263

Caloric Requirements

• First trimester: Energy needs are similar to those of non-pregnant women
• Second trimester: Approximately +340 kcal/day above baseline
• Third trimester: Approximately +450 kcal/day above baseline
• Final adjustments are made based on prepregnancy weight, age, and physical activity level

• Guyton & Hall Textbook of Medical Physiology, p. 1039
• Creasy & Resnik's Maternal-Fetal Medicine, p. 264

Macronutrient Distribution (2nd Trimester, 2330 kcal/day example)

Micronutrient Requirements

Folic Acid (Folate)

• All women capable of pregnancy: 400 mcg/day of synthetic folic acid (in addition to dietary folate)
• Previous NTD-affected pregnancy: 4 mg/day starting 1 month before conception through first trimester
• Deficiency causes neural tube defects (NTDs), impairs red blood cell synthesis, and is associated with spontaneous preterm birth
• Rich sources: beef liver, spinach, black-eyed peas, asparagus, broccoli, avocado, fortified cereals
• Creasy & Resnik's Maternal-Fetal Medicine, p. 265

Iron

• 30 mg/day starting early in pregnancy (universal recommendation per CDC)
• Fetus requires ~375 mg of iron for blood formation; mother needs an additional ~600 mg for her expanded blood volume
• Maternal iron stores at the start of pregnancy are often only 100-700 mg, so without adequate dietary iron, hypochromic anemia results
• Guyton & Hall, p. 1039; Creasy & Resnik, p. 264

Calcium & Phosphate

• Stored by the mother early in pregnancy and mobilized for fetal bone development
• Deficiency leads to maternal bone demineralization

Vitamin D

• Recommended dietary allowance: 600 IU/day (IOM recommendation)
• Endocrine Society suggests 4000 IU/day for pregnant women to achieve optimal serum 25(OH)D (75-100 nmol/L)
• ACOG does not recommend universal screening but advises 1000-2000 IU/day if deficiency is confirmed
• Critical for calcium absorption; deficiency jeopardizes maternal and fetal bone mass
• Rich sources: cod liver oil (1400 IU/tbsp), salmon (450 IU), tuna, fortified milk, eggs
• Creasy & Resnik's Maternal-Fetal Medicine, p. 266

Vitamin K

• Often supplemented shortly before delivery so the neonate has sufficient prothrombin to prevent hemorrhage (especially intracranial hemorrhage) from birth trauma
• Guyton & Hall, p. 1039

Iodine, Choline, Vitamin A, Vitamin C

• Iodine and choline have specific increased requirements in pregnancy per the 2020 Dietary Guidelines
• Vitamin A: 770 mcg/day; Vitamin C: 85 mg/day (increased from non-pregnant values)

Food Group Guidance (MyPlate for Pregnancy)

• Creasy & Resnik's Maternal-Fetal Medicine, p. 264

Dietary Limits

• Sodium: < 2300 mg/day
• Saturated fat: < 10% of calories/day (or < 27 g/day at 2400 kcal)
• Added sugars: < 10% of calories/day (or < 60 g/day)
• Alcohol: Contraindicated throughout pregnancy
• Caffeine: Limit to < 200 mg/day (ACOG recommendation)

Dietary Supplementation

• Prenatal vitamins are routinely recommended given the high prevalence of dietary inadequacies
• Women at particularly high nutritional risk requiring careful evaluation and supplementation:
  • Multiple gestations
  • Adolescents
  • Vegan diet
  • Substance use disorder
  • Malabsorption syndromes or history of bariatric surgery
• Creasy & Resnik's Maternal-Fetal Medicine, p. 264

Foods to Avoid

• Raw or undercooked meats and seafood (risk of Listeria, Toxoplasma, Salmonella)
• High-mercury fish (shark, swordfish, king mackerel, tilefish)
• Unpasteurized dairy products and soft cheeses
• Raw sprouts
• Excessive Vitamin A (teratogenic in high doses - avoid liver in large amounts and retinoid supplements)

Gestational Weight Gain Guidelines (IOM)

• Creasy & Resnik's Maternal-Fetal Medicine, p. 263

Key Points Summary

1. Diet in pregnancy should be nutrient-dense, not just calorie-rich
2. Extra calories needed only from the 2nd trimester onwards (+340 kcal) and more in the 3rd (+450 kcal)
3. Folic acid (400 mcg/day pre-conceptionally and throughout 1st trimester) is the single most important supplement to prevent NTDs
4. Iron supplementation (30 mg/day) is universally recommended to prevent hypochromic anemia
5. Vitamin D and calcium are critical for fetal bone development
6. Avoid alcohol completely; limit caffeine; avoid high-mercury fish and undercooked foods
7. Women with special risk factors (vegan, malabsorption, multiple pregnancy) require tailored assessment