The first trimester is a crucial time for the healthy development of your baby, and being mindful of your diet is essential. foods to avoid when pregnant first trimester. These include raw or undercooked eggs, unpasteurized dairy products, and raw seafood, which can harbor harmful bacteria. High-mercury fish, like shark and swordfish, should also be off the menu. Undercooked meat and excessive caffeine consumption are best avoided. By staying informed and making these dietary adjustments, you're taking a significant step toward a healthier pregnancy. Share your experiences and tips with our forum community to support and empower fellow moms-to-be.