Pregnancy, Lactation, And Infancy Pregnant and lacating women, infants, children, adolescents, and adults need same nutrients, but the amounts they need vary depending on their stage of life. A whole new life begins at conception. Organ system develop rapidly, and nutrition plays many supportive roles. A placenta is the organ that develops inside the uterus early in pregnacy. Maternal nutrition before and during pregnancy affects both the mother's health and the infants growth. As the infant develops through its three stages- the zygote, embryo, and the fetus. Its organs and tissues grow. Time of intense development are critical peroids that dep