There is no strong evidence that foundation, by itself, is directly harmful to the baby. Concerns are usually about skin irritation, allergy, acne flares, and ingredient preferences. Pregnancy can change skin sensitivity and oil balance, so choose simpler, fragrance-free, non-comedogenic formulas designed for sensitive skin. If you want to be extra conservative, use a separate mineral sunscreen underneath and apply foundation on top. Hygiene matters: remove makeup thoroughly, clean brushes and sponges, and discontinue any product that causes burning, itching, or persistent redness.