How long is a baby in the womb for? http://wiki.answers.com/Q/How_long_is_a_baby_in_the_womb_for&src=rss0. A human baby is in the womb for about 9 months.How long are baby fish in the womb?ow long is a baby in the womb for? http://wiki.answers.com/Q/How_long_is_a_baby_in_the_womb_for&src=rss0. A human baby is in the womb for about 9 months. How long are baby fish in the womb?