Here you shall find a clarification of the different stages of fetal growth, from the very first stage, called zygote, to the last phase, in which it is known as fetus. It will be called this way up until childbirth.
That week marks the finish of the first month, there are no important physical nor emotional changes. If they are not tested, they don’t even realise they are pregnant.
Some medications may cause problems during pregnancy by passing to your baby through the placenta. There is a classification of medicines according to their damaging effect on the foetus. However, the ideal thing would be that women do not take any medication during pregnancy.