I should have learned my lesson when the first Ben Wa ball fell out, but I really thought I had the situation under control.

I arrived at my friend Maree’s house for a typical night of wearing pajamas, drinking wine, catching up on “Girls” and eating salad and chocolate.

When I walked in the door, she dropped a bomb on me. John, a guy she was trying to fix me up with, was going to stop by. After the initial panic, I decided it was entirely appropriate for him to meet me in pajamas. (Although I did wish I’d bothered to put some underwear on.)

All was forgiven as soon as Maree announced she had a “naughty gift” for me. She then presented me with a pretty little silk bag of Ben Wa balls.

Thanks to soft-porn Chick Lit like “Fifty Shades of Grey,” roughly 97 percent of American women know what Ben Wa balls are. But if you’re in the dark, Ben Wa balls, which reportedly date back to 500 A.D., are weighted stainless-steel spheres that, when inserted in the vagina, help women strengthen their vaginal and pelvic floor muscles.

Like dumbbells, Ben Wa balls vary in size and weight, and they usually come in pairs. Using Ben Wa balls can have all kinds of health benefits, such as preventing and treating incontinence or — a term that any mother is familiar with, and any childless woman has a diabolical fear of — uterine prolapse. (Google it, boys.)

Since they’re also handy for increasing arousal, Ben Wa balls have a decidedly more sexy benefit: better and more frequent orgasms. And they’re remarkably convenient. When you’re clothed, nobody can see what’s inside your vagina, so you can use them whenever you want. What’s not to love about the prospect of toning your vaginal muscles while you’re just living your life? We women love to multitask.

The ones Maree gave me were roughly the size of those bouncy balls you get out of vending machines. Since I’m by nature impatient and an overachiever, I announced that I was putting both Ben Wa balls in immediately.

“Maybe you should just start with one?” Maree timidly suggested.

Who has time for just one Ben Wa ball? Unless your vagina is capable of signing up for a 5K, it’s all on you to get in shape, girl.

The balls slid in easily, which I announced loudly from the bathroom. Initially, they were a bit cold, but they warmed up quickly. As I walked into the dining room, I felt them subtly shifting. Hey, that’s kind of nice, I thought. This isn’t so hard.

And then, I coughed. One ball shot right out, sending me into a knock-kneed squat in attempt to catch it with my thigh.

“I told you to start with one!” Maree said.

Maybe she had a point. I decided that one ball was enough for the rest of the evening. You wouldn’t bench-press 200 pounds on your first try, would you?

Since Maree bought a pair for herself, I convinced her to put one ball in. It felt a little weird if I was the only one doing secret vaginal aerobics, especially with John coming over.

With one Ben Wa ball each securely in place, Maree and I sat down at the dining room table, dug in to our big salads. At this point, John arrived, so I started to rise from my chair to introduce myself.

The abrupt motion of getting up from my chair provided just enough force for the other Ben Wa ball to cannonball out of its hiding place. I clenched my thighs together before the ball could escape out of the bottom of my pajama pants leg. I hovered above my chair, terrified to make any sudden movement.

“I’m sorry, but … I can’t get up right now!” I stuttered. I felt my face flush. John eyed me suspiciously, which sent me into an uncontrollable fit of laughter. Maree descended down the same spiral of laughter. Poor John looked incredibly confused.

Maree led John on a tour of her house to distract him, buying me time to run to the bathroom to take care of my ball situation. From the bathroom, I heard her squeal, “Um, excuse me, John. I just need to run to the restroom.”

We have another runaway Ben Wa ball, people.

When everyone returned to the dining room — the ladies sans balls — Maree and I felt rude for not letting John in on the joke. So we explained what happened. If it rattled him, he didn’t show it.

Lest you think Maree and I have supernaturally large or extremely unfit vaginas or something, I’d like to point out that these balls are much heavier than you’d expect. Even though both Maree and I can rock a power yoga class, apparently our vaginas could benefit from some resistance training.

And I’m not calling your vagina fat or anything, but yours could probably use a little exercise, too.