Preconception care is a key element of modern perinatal healthcare, significantly influencing the health of the mother, fetus, and future population. Current evidence highlights the importance of the health status of the woman (and her partner) even before conception—the so-called “zero trimester”—as a determinant of successful pregnancy, optimal fetal development, and prevention of pregnancy complications. This review summarizes the latest knowledge in the fields of nutrition, supplementation (folic acid, choline, vitamin D, iodine), obesity prevention, and general medical measures such as dental check-ups and vaccination. It also emphasizes the need for an organized, multidisciplinary approach to preconception care at the level of healthcare systems.