Pregnancy will put any marriage to the test.
Nausea, stress and deadlines, reexamining your priorities, in-laws pressuring you to do this and that. It can make for physically and mentally challenging times.
It can also bring expectant couples closer together.
Well into their second trimester, Kate Middleton and Prince William are cruising to parenthood more demonstrably (and demonstratively) in love than ever.
"They're much more touchy-feely than they were," notes royal photographer Mark Stewart. "They've always been close, but it is much more pronounced."
"There appears to be a new, deeper bond between them."
They've certainly been enjoying each other's company.
From opposite ends of the Ping-Pong table, the famously competitive parents of Britain's future monarch acted like kids during a recent trip to Scotland.
"Ahem, I think that was 6-2," William said, declaring victory over Kate following their visit to a Glasgow sports center April 4. With one caveat, of course.
"The only reason I won today was because Catherine is pregnant," he added later. "Otherwise she would have taken off her coat and beat me."
That same day, in chatting with homeless youth at a Quarriers shelter, Will praised Kate's cooking, pointing to his allegedly expanding waistline.
"He isn't very good in the kitchen," Kate Middleton teased of her better half.
All kidding aside, the affection and tenderness between them speaks volumes.
"The eye [contact], their smiles, were very genuine, caring," says a People source. "You know when you're in a restaurant and see two people obviously in love?"
"That's what they're like."