Pregnancy vitamin deficiencies, artwork. Vitamin deficiencies in pregnancy and childhood. Foetal demand for nutrients can cause a mother to be deficient in certain vitamins. In early pregnancy the foetus requires folic acid. This can cause megaloblastic anaemia in the mother, whose red blood cells (pink, lower left) become inefficient at carrying oxygen. Extra demand for vitamin D can cause osteomalacia, demineralization and softening of the bone matrix (yellow, lower right). This condition is known as rickets in children, and can affect a breastfeeding baby (upper left), causing bowing of the leg bones (upper right) as it grows.