Bundle of Trouble (A Maternal Instincts Mystery) by Diana Orgain.
This is a charming debut! The story begins when the phone rings as Kate Connelly and her husband Jim are watching a football game. It turns out to be the San Francisco medical examiner, asking for information about Jim's brother George, whose belongings have been found on a pier at the same time as a drowned corpse.
A few minutes later, Kate goes into labour, and they rush to the hospital, forgetting about the phone call. Eventually, they learn that George is just fine, although he seems to not wish to be found.
After Kate gets home, she goes to collect George's things from the police station and runs into an old high school friend Michelle. It turns out that Michelle is identifying the body, who happens to be her estranged husband Brad. Michelle invites Kate over for lunch, and during their discussion, it emerges that George worked for Brad.
This all seems too coincidental and suspicious to Kate, and she decides to figure out what exactly is going on. Kate enjoys this so much, and is so reluctant to leave her child and return to her job (although her income is necessary) that she begins to consider private investigation as a career.
This light mystery was a quick and enjoyable read. I just discovered that the second book in the series was released today, and will definitely be picking it up.