One thing they don’t tell you in “What to Expect When You’re Expecting,” “The Girlfriends’ Guide to Pregnancy” or any of the other pregnancy guidebooks – if memory serves -- is how big your fetus is using Big Macs as a unit of measure.

Oh, sure, pregnant women have any number of places they can find out how big their babies are in terms of fruits and vegetables. Parents, BabyCenter and The Bump will all estimate the length and weight of your fetus using, for comparison, everything from a poppy seed to a watermelon – with plenty of pomegranate seeds and pineapples, in between.

But just because you’re supposed eat healthily during pregnancy (boxed macaroni and cheese and chocolate milkshakes are healthy, right?) doesn’t mean your every thought has to be healthy, darn it. Why can’t you measure the growth of your fetus in, say, Big Macs?

That seems to be the thinking behind howmanybigmacsismybaby.com, a website that, as its URL accurately indicates, answers the question “How Many Big Macs Is My Baby?” Judging from the attention it has been getting of late (see coverage by The Takeout and Food and Wine), a site that allows women (and their partners) to track growth in utero using Big Macs as a yardstick is an idea whose time has come (and in fact may be long overdue).

The online calculator is pretty simple to use: Just plug in the number of weeks you’ve been pregnant and – voila – a Big Mac translation will be provided. So you’ll soon learn that at 12 weeks along, your baby is “less than 1 Big Mac” in size, while at 40 weeks you’re carrying a fetus the size of 16 Big Macs.

Ooof.

“This page is NOT official licensed by McDonald's,” the site’s fine print notes. “It was just a random fun idea created by the comedienne Nickey Winkelman to describe the size of her baby in something more relatable than Kale.”

Genius.

Photo: GettyImages