The expert argues it relates to men's fear that their "fun lives" will be gone after fatherhood as they think of the baby as a responsibility that will be too much to handle.
Dr Shira Danzig, a pregnancy and pre-pregnancy therapist, argues that it is also a lot more biological than that. According to the expert, pregnancy often means men's sex lives aren't as fulfilling and so men cheat just to satisfy a physical desire.
"You can be absolutely struggling with your sex life when a woman is pregnant," she told Personal Space.
Some men might also cheat because they feel like they are not getting enough attention from their partner, who is trying to cope with the reality of growing a human being inside her body.
"In my research — and I've been looking at relationships and following them over time with 370 couples for 30 years, funded by the National Institutes of Health — the main reason men have affairs is that they're not being noticed. They desire affirmation, to be validated, to be seen, and not be taken for granted. So that has nothing to do with being pregnant," Dr Terri Orbuch, a professor at Oakland University and author of 5 Simple Steps to Take Your Marriage to Good to Great told People magazine.
However, the expert argues that, in terms of evolution, a man should actually want to keep his pregnant partner closer during that time.
"There is an evolutionary desire to procreate, and have their genes be passed on from generation to generation," she explains.
However, men who hold positions of power (such as big name NBA players like Thompson) are said to be more likely to cheat.
"First, it's the notion of invulnerability — they really don't think that they'll get caught, and they assume that even if they do get caught that they won't get in trouble because they have the resources or the people who will cover it up," she told the magazine.
Stressful jobs are also play a part in making men "crave excitement".
For Orbuch, it all comes down to a need for validation in their lives.
"So when you're used to high-stress and excitement, you might seek it out in affairs because your current relationship doesn't have that. I call these people adrenaline junkies, because they're dependent on this rush."
Fear of being left out could also be to blame.
According to Dr Scott Haltzman, author of The Secrets of Happily Married Women, "for many men, engaging in sex is a form of emotional closeness".
"When their partners push them away, they feel rejected not just sexually, but also emotionally."
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