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.
The husband who has more than one wife is obliged to observe justice and equality among his wives in terms of overnight stay. Shaykhul-Islam Ibn Taymiyyah wrote:
"He is obliged to treat both wives equally according to the consensus of the Muslims. In the four Sunan (the hadeeth collections compiled by Abu Daawood, An-Nasaa'i, At-Tirmithi and Ibn Maajah), it is narrated on the authority of Abu Hurayrah that the Prophet said, 'Whoever has two wives…' So he is obliged to divide his time equally. If he stays overnight with one wife for one or two or three nights, then he must stay overnight with the other for the same amount of time, and he should not favor one of them in the division of his time."
If the situation is as you described and your husband stayed with his other wife for such amount of days, then he is obliged to make up for these days with you. Ibn Qudaamah wrote, "...and if he is unable to spend the night with one of his wives due to work or detainment, or he failed to observe her right to overnight stay for no valid excuse, then he has to make it up for that with her." [Al-Mughni]
The fact that he was helping her when she gave birth is not a valid excuse that cancels your right to overnight stay in your due turn. For more benefit, please refer to fatwa 222133.
Allaah knows best.