Hope the Muslim ladies out there can help!....

My OH and I aren't married yet, mainly due to the cost of it all. We hope to have a nikah as soon as we can however. We are getting older now and wary of waiting much longer to TTC as we are late 30's and early 40's. My question is this ..... if we were to manage to get pregnant before marriage etc, where would this leave my OH who is a Muslim religiously? I am a different religion so it doesn't matter so much to me. I'm aware he shouldn't even have a gf but we are very much in love. I know sex before marriage is a big no but we are not sure if we want to risk waiting for children much longer. Hope you have some helpful answers everyone! Thanks x