What should a pregnant woman eat during the fourth month of pregnancy to benefit the fetus?

During the fourth month of pregnancy—roughly weeks 13 through 16—the fetus undergoes rapid development, including the formation of major organs, early bone mineralization, and the beginning of fetal movement (though it may not yet be perceptible to the mother). Nutrition during this stage plays a critical role in supporting healthy growth and reducing risks of complications. A balanced, nutrient-dense diet is essential.

Key nutrients to prioritize include: iron, to support expanding maternal blood volume and prevent iron-deficiency anemia; folic acid (vitamin B9), which remains vital for neural tube and cellular development; calcium and vitamin D, crucial for early skeletal ossification; omega-3 fatty acids (especially DHA), important for fetal brain and retinal development; and high-quality protein, needed for tissue growth and placental function. Adequate hydration and fiber intake also help mitigate common second-trimester concerns like constipation and urinary tract infections.

Practical food choices include lean proteins such as cooked salmon (low-mercury), eggs, lentils, and skinless poultry; leafy green vegetables (spinach, kale) and legumes for folate and iron; fortified cereals or dairy alternatives for calcium and vitamin D; and nuts (e.g., walnuts) or chia seeds for plant-based omega-3s. It’s important to avoid raw or undercooked seafood, meat, and eggs; unpasteurized dairy or juices; and high-mercury fish (e.g., swordfish, king mackerel). Caffeine should be limited to ≤200 mg per day (about one 12-oz cup of coffee).

Supplementation should be guided by prenatal care providers. Most individuals continue taking a daily prenatal vitamin containing at least 400–600 mcg of folic acid and 27 mg of elemental iron. Vitamin D supplementation (600–800 IU/day) and DHA (200–300 mg/day) are often recommended, especially if dietary intake is insufficient. Always consult your obstetrician or registered dietitian before starting or adjusting supplements.