All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
It is permissible for women after giving birth to a child to travel before she becomes pure as there is no relation between her becoming pure and travelling. There is no text from the Book of Allaah or the Sunnah of the Prophet that prohibits women from travelling after childbirth [before becoming pure]. It is reported in the Sunnah that women can travel after giving birth to the baby. Asmaa' Bint 'Umays, the wife of Abu Bakr gave birth to Mohammad at Thul-Hulayfah, in her way to Hajj. 'Aa'ishah was in menses as well while on her way to Hajj.
However, when a woman travels, she must be accompanied by her husband or a Mahram (a non-marriageable relative). The Prophet said: "A woman should not travel except with a Mahram, and a man should not enter onto her except in the presence of one of her Mahaarim (plural of Mahram)." A man asked the Prophet I want to go out in a battle with such and such army, and my wife wants to go for Hajj, what shall I do? The Prophet replied: "Accompany her." [Al-Bukhari] Besides, it is a condition that her travel not be to perform an act of disobedience.
Allaah knows best.