It's a conundrum which has raised a few eyebrows.
One man has recently been told that he's going to be a dad, but rather than joy, he's feeling pretty conflicted.
The couple had their hearts set on starting a family but were dealt a blow last December when the husband was diagnosed with azoospermia, which is essentially blockage of the pipes.
As a result, he's regarding his wife's miracle pregnancy with a little suspicion and turned to Reddit for some advice.
"My wife and I have been married for three years, together for six," he wrote.
"She's always been one of the most amazing people I've ever met.
"No huge fights, love languages match up, and we're both fairly active people which has been why we've always had a really strong relationship for so long.
"That's why this is so difficult for me."
Following the diagnosis in December, the husband had surgery to rectify his condition booked for this coming July.
He continues: "She's got a high sex drive as do I, so we've still been very sexually active, but there should've been no way I could have gotten her pregnant.
"She missed her period this week. I couldn't imagine that she might actually be pregnant, right? The babies are bottled in until they get the blockage out. She took three tests though, and sure enough they're all positive."
Now he's feeling a lot of different emotions.
At first he was stunned - and his wife is "ecstatic" - but now he's looking for clues that she might have been unfaithful.
While she's "given no indication of any guilt or worry that she may have cheated", he adds: "Her job often has her taking clients out for dinner and it's not uncommon for her to get back later in the evening.
"She always wears one of the same two perfumes, but she came back one night smelling completely different. I remember seeing a text message on her lock screen of just a winky face, a different time, but assumed it was one of her girlfriends."
The man ends by explaining that he's booked to see a doctor in secret to see if there's any way the baby could be his.
Apparently, it's not all bad news. The conclusion seemed to be that while the husband should be cautious of getting too excited, it wasn't a medical impossibility.
"I literally just studied this!" wrote one person. "OK, so although you’ve been diagnosed with azoospermia it means that when they looked at your semen in the lab it didn't have any sperm in it.
"However, you produce a lot of semen and the lab only looks at a tiny fraction of it which usually gives a good response.
"Usually you would repeat several times before concluding it's azoospermia, although just because the lab didn't see any sperm it can just mean that you had an incredibly low count so none of their samples from the sample you have showed any."
