This sanskar is performed from preconception to the time of conception. The Garbhadhan sanskar is done to overcome any defect in the ovum and foetus to purify the womb.
Since ancient times it has been known that the child in the womb adopts impressions from its surroundings and the behavior of its mother and also started learning things.
There are three type of treatment, first is pre-conception, second is during preganancy and third is after delivery.