Vitamin D deficiency.
Rickets is a poor and clinical marker for poor, and pre and post natal bone health, caused by Vitamin d deficiency. Vitamin d deficiency and ricket cases are coming back again. There has been talk of giving Vitamin D supplementation to prenatal women and breastfeeding women, as it is unlikely you can not eat enough Vitamin D.
You can get it in wholegrain bread and cereals, dark green leafy vegetables, citrus fruits, dairy produce, lean meat, fish, and poultry.