Drunken Partying

Married at 19 and at 20 my wife was having our first child, and she had a boy. But she had to stay in hospital a few extra days, as the baby was larger than normal. She was okay just needed to recover from the delivery. Her mother (39) and me were celebrating at home and we got drunk. I (24) and my mother-in-law party long and hard, we awoke next morning in the same bed naked, and we'd had sex. Only problem I hadn't used a condom, and my mother-in-law was on anything either. Being divorced and she wasn't dating she didn't see the need. She is also a born again Christian and a pillar of society, my wife could see something was wrong on my next visit. I'm not a great liar and so told her about our drinking and us having sex. Once she stopped laughing, as she thought it very funny, her strait-laced mother and me having sex. Not long after that her mother came in and my wife burst out laughing again. Her mother realized I had told her everything and told my wife she didn't think she'll get pregnant from the one sexual encounter. My wife replied That was my thinking also and started laughing again. A few days later my wife was home and still thought it funny her mother and I had fucked. To tease her mother, she started suggesting names for any child she might have. I wasn't in any trouble as my wife, knew we were drunk, and she had been there done that herself. Anyway, it was more fun for her to tease her mother. But I wonder if she would have kept laughing if her mother had gotten pregnant. But it hasn't stop her asking her mother to join us in a threesome.