This is How It Always Is by Laurie Frankel

 This was a popular book last year that I would have missed completely if it wasn't for my niece.  She came to visit and dropped a lot of great reading ideas on us, and this was one of them.  Since I was about to leave the country, and am always looking for something that is manageable to read while I am a bit jet lagged and burning the candle at both ends, which often leaves almost no time for reading.
In this story, Rosie is an emergency room doctor and Penn is an author.  They have what will sound very typical to parents, which is once they have four children, all boys, they find that they lose themselves and are ruled by their young brood.  Then Rosie decides to have a fifth child, all the while hoping for a girl.  Her reasons are more deep seeded than most, in that her younger sister, Poppy, died of cancer when she was a child, and Rosie is seeking to recreate that relationship.  So, despite being a woman of science, she follows all the old wives tales and dreams of her daughter up to the delivery room, where her son Claude is born.  Claude starts wearing dresses as a toddler, and the book is largely about Claude becoming Poppy and all the hurdles that a transgender child faces, and never gets back to examine Rosie's psyche.  It is an easy route to thinking about what one would do should this come about in your house.