The Cow - 2:235
There is no sin on you for informing them of your proposal of marriage, or for keeping this intention within you. Allah knows what you think about them. Do not meet them in secret except for the purpose of talking to them in a proper and virtuous manner. And do not attempt to marry them before their waiting period has expired. Know that Allah knows what is in you, so beware of Him. And know that Allah is Forgiving, Compassionate.
How long is the waiting period for women when they are divorced?
The Cow/2:228
The divorced women should wait three months for themselves (before marrying another). It is not fitting for them to conceal what Allah has created in their wombs if they believe in Allah and the Last Day. In that case (if they become pregnant) their husbands have more right to take them back if they wish to reconcile. Women have equal rights over men as men have rights over women, and men have a rank over them (in case of pregnancy). Allah is Mighty, Wise.
Divorce/65:4
As for your women who have gone through menopause and have stopped menstruating, if you are in doubt, their waiting period is three months. And those who do not menstruate and are pregnant, their period ends when they give up their burdens. Whoever listens to Allah, He will make it easy for him.