21.2 Nutrition in Pregnancy and Lactation: Physiology, Needs, Meal Patterns, and Problems
Key Takeaways
The PDRI 2015 adds 300 kcal/day in the second and third trimesters and 500 kcal/day during lactation, plus 27 g of protein for both.
Folic acid before conception and in early pregnancy prevents neural tube defects, which form within the first 28 days after conception.
Gestational diabetes is diagnosed by a 75 g oral glucose tolerance test when fasting glucose is 92 mg/dL or more, 1-hour glucose 180 mg/dL or more, or 2-hour glucose 153 mg/dL or more.
Pregnant women should avoid alcohol and large predatory fish high in methylmercury, such as shark, swordfish, and marlin, while still eating low-mercury fish.
During lactation, prolactin stimulates milk production and oxytocin triggers the let-down reflex, so frequent effective suckling maintains supply.
The life cycle competency area carries 20% of the Community and Public Health Nutrition subject. Gestational weight gain, the PDRI values for pregnancy, and maternal assessment are in the life-stage assessment section, and breastfeeding policy is in the IYCF section; this section covers the physiology, meal planning, and problems of pregnancy and lactation.
Physiological Changes in Pregnancy
- Blood volume increases by about 45-50%, while red cell mass rises less, causing physiologic hemodilution (lower hemoglobin concentration).
- Placenta: produces hormones (hCG, human placental lactogen, estrogen, progesterone) and transfers nutrients and oxygen.
- Insulin resistance rises in the second half of pregnancy to direct glucose to the fetus.
- Gastrointestinal changes: progesterone relaxes smooth muscle, slowing digestion and causing heartburn and constipation.
- Kidney: glomerular filtration increases.
- Nutrient absorption of iron and calcium increases.
Critical periods: organs form during the first trimester (embryonic period). The neural tube closes within about 28 days after conception, often before a woman knows she is pregnant, which is why folic acid is advised before conception.
Key Nutrients and Their Roles
| Nutrient | Role | Food sources and notes |
|---|---|---|
| Energy | Fetal growth, maternal tissues | +300 kcal/day in 2nd and 3rd trimesters (PDRI 2015) |
| Protein | Tissue synthesis | +27 g/day: fish, eggs, legumes, lean meat, milk |
| Folate | DNA synthesis; prevents neural tube defects | Green leafy vegetables, legumes; daily iron-folic acid supplement |
| Iron | Expanded blood volume, fetal stores | Meat, liver, fish, legumes with vitamin C; needs cannot be met by diet alone, so supplements are given |
| Iodine | Fetal brain development, thyroid function | Iodized salt, seafood; +100 µg/day |
| Calcium | Fetal skeleton | Milk, small fish eaten with bones, tofu; WHO recommends calcium supplements in populations with low intake to reduce pre-eclampsia risk |
| Vitamin A | Cell growth, immunity | Yellow and green vegetables, liver in moderation; high-dose supplements avoided |
| DHA (omega-3) | Fetal brain and retina | Fatty fish such as sardines and galunggong |
Meal Pattern for Pregnancy
For a 25-year-old woman in her second trimester, the PDRI gives about 2,230 kcal (1,930 + 300) and 89 g protein (62 + 27). A Pinggang Pinoy-based day:
- Breakfast: rice or pandesal, egg, sliced papaya, milk
- Snack: boiled saba banana or camote
- Lunch: rice, fish sinigang with kangkong and radish, fruit
- Snack: taho or milk with crackers
- Dinner: rice, chicken tinola with malunggay and green papaya, fruit
- Throughout: water, iodized salt, daily iron-folic acid as prescribed
Common Discomforts
| Discomfort | Nutrition management |
|---|---|
| Nausea and vomiting | Small, frequent dry meals; crackers before rising; avoid strong odors; ginger may help. Hyperemesis gravidarum (severe vomiting with weight loss and dehydration) needs medical care |
| Heartburn | Small meals; avoid lying down after eating; limit fatty and spicy foods |
| Constipation | Fiber, fluids, physical activity; iron supplements may worsen it |
| Leg cramps | Adequate calcium, magnesium, and fluids; stretching |
| Pica | Craving non-food items such as soil or ice; screen for iron deficiency |
| Edema | Mild edema is normal; sudden swelling with high blood pressure needs evaluation for pre-eclampsia |
High-Risk Conditions
- Adolescent pregnancy: the mother is still growing, so she competes with the fetus for nutrients; higher risk of low birth weight and anemia; needs extra energy, protein, calcium, and iron, plus counseling.
- Anemia: hemoglobin below 110 g/L in the first and third trimesters and below 105 g/L in the second (WHO 2024); give iron-folic acid, treat parasites, and improve diet.
- Gestational diabetes (GDM): diagnosed with a 75 g oral glucose tolerance test (fasting 92 mg/dL or more, 1-hour 180 or more, or 2-hour 153 or more; one value is enough). Management: carbohydrate distributed across three meals and two to three snacks including a bedtime snack, limited simple sugars, enough energy for appropriate weight gain, physical activity, and glucose monitoring. Insulin is used if targets are not met.
- Pre-eclampsia: high blood pressure with protein in urine after 20 weeks; calcium supplementation in low-intake populations reduces risk; sodium restriction is not used to prevent it.
- Underweight or overweight before pregnancy: adjust weight gain targets.
- Multiple pregnancy: higher energy and weight gain needs.
Food Safety and Substances to Avoid
- Alcohol: no safe amount in pregnancy (fetal alcohol spectrum disorders).
- Caffeine: limit; many guidelines advise under about 200-300 mg/day.
- Methylmercury: avoid shark, swordfish, king mackerel, and marlin; choose low-mercury fish two to three times a week.
- Listeria and toxoplasma: avoid unpasteurized milk, undercooked meat and eggs, and refrigerated ready-to-eat foods that have not been reheated; wash vegetables.
- Smoking and secondhand smoke lower birth weight.
- Herbal products of unknown safety should be avoided.
Nutrition During Lactation
Physiology: suckling stimulates prolactin, which drives milk production, and oxytocin, which causes the let-down (milk ejection) reflex. Colostrum (first days) is rich in antibodies, protein, and vitamin A. Transitional milk follows, then mature milk. Within a feed, foremilk is more watery and hindmilk is richer in fat.
Needs (PDRI 2015): +500 kcal and +27 g protein a day, with extra water (+700 mL), iodine (+100 µg), and vitamin A (+400 µg RE).
Practical points:
- Milk quantity is maintained in most mothers even with modest diets, but the levels of iodine, DHA, and some water-soluble vitamins depend on the mother's intake.
- Drink to thirst and with each feed.
- Gradual weight loss after delivery is compatible with breastfeeding; avoid crash diets.
- Frequent, effective feeding on demand is the best way to increase supply.
- Common problems: engorgement and mastitis are managed by continued breastfeeding or expressing, correct attachment, and medical care for infection.
- Working mothers can express and store milk using workplace lactation stations and breaks under RA 10028.
A 22-year-old woman in her third trimester has a PDRI energy requirement of 1,930 kcal when not pregnant. What is her energy recommendation now?
1,930 kcal
2,430 kcal
2,230 kcal
2,730 kcal
A pregnant woman takes a 75 g oral glucose tolerance test. Her fasting glucose is 88 mg/dL, 1-hour glucose is 172 mg/dL, and 2-hour glucose is 158 mg/dL. How should the result be interpreted?
Normal, because the fasting value is still below the 92 mg/dL cutoff
Gestational diabetes, because the 2-hour value is 153 mg/dL or more
Normal, because two of three values are normal
Type 1 diabetes requiring insulin immediately
A breastfeeding mother worries that her milk supply is low. What advice best increases milk production?
Give formula between feeds so the breasts can rest
Drink large amounts of milk every day
Feed on a strict 4-hour schedule
Breastfeed frequently and effectively on demand
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