Poor maternal nutrition status is of a prime health concern as it not only has major health risks for the mother and subsequent pregnancy and birth outcomes but goes further beyond to impact child growth and cognitive development and possibly has transgenerational consequences. The effects of the maternal undernutrition on fetal health can originate in different time periods and mechanisms and can be divided to (i) preconceptional, (ii) periconceptional, (iii) early and late pregnancy, and (iv) postnatal associated with breastfeeding or late nutrition. From the perspective of nutrients, the maternal nutritional factor influencing the fetal growth or health can be seen as (i) acute, associated with the actual composition of maternal nutrition at a given time, and (ii) long-term, associated with maternal long-term nutritional status. This chapter discusses the known pathophysiological mechanisms, through which maternal undernutrition impacts the growth as well as the health of the offspring, and provides also a brief overview of epidemiology of this condition.