Much is made of the non-maternity clothes an expectant mother can wear during pregnancy — the wrap dresses, the leggings, the boxy shift dress-turned-tunic top — but some maternity clothes also do double duty once the baby is born, especially in the period not always affectionately dubbed “the fourth trimester.”

“For the four months after the baby, most women are in their fourth trimester. It’s camouflage-clothes redux,” says Amy Tara Koch, author of the new book “Bump It Up,” published by Ballantine Books. “You don’t want to look fat, but you don’t have the bump to hide behind.”

The loose, long cardigan is a must.

“The beauty of a draped cardigan — look for one without buttons — is it hangs down off you,” says Paula Motte, senior editor at BabyCenter.com. “It the wardrobe essential that takes you through pregnancy and beyond. You look for one with drape-y, forgiving fabric in a cotton-stretch blend, and you wear it over everything.”

Koch likes the look of the sweater, especially post-baby, because as your shape slims, the sweater just looks longer. “The biggest mistake most women make is proportion. It’s an understandable mistake, you feel gigantic so you wear gigantic clothes. But that makes you immediately look frumpy,” she says.

With that key sweater, wear leggings, Koch suggests, which also complement tunics. The opposite silhouette also can work: a long maxi skirt with a slim tank top. “You need volume control,” Koch says.

Actress Leigh-Allyn Baker started work on her new Disney show “Good Luck Charlie,” in which she plays the mother of an infant, right after her own son was born.

“I had to invest when I was pregnant in great jeans. I got Joe’s Jeans, which are made for curvy people anyway. I wore them up until a few months ago — long after the baby. They don’t press on your belly because they’re low-slung and have no waistband, but they show off the legs,” Baker said.

Some premium denim lines have maternity lines, Koch says, but you can also take jeans you already own to the tailor and have them put in a panel of pantyhose fabric or Spandex over the belly. Those will become your go-to jeans, even post-pregnancy, she says.

And if you buy them a little bigger than your pre-pregnancy size, no one has to know, Motte adds. “Your tailor is your friend. Buy clothes that fit you now — even if it’s not the size you wore before being pregnant. You’ll have clothes to go the distance, and you can always remove side stretchy panels or have seams taken in or out.”

Since her belly was biggest in the summer, Baker bought bikini separates to accommodate the vastly different sized top and bottom of her body. Her biggest “expansion” came at the bustline so she sized up there and bought bottoms that she’s still able to wear. (If the occasion rises again, Baker adds, she’ll buy two tops for that same pair of bottoms — one in her pregnant size and the other in her regular size.)

And she’s still wearing maternity tank tops, which now hit well below the hip. Again, she likes the elongated look they give. The key, she says, is that throughout her pregnancy — and now beyond — she is looking for fitted, comfortable fabrics.

“It’s not about ‘maternity,’ it’s just about the right material. Fabric is much more important than shape,” Baker says.

Motte agrees about the fabric. Choose the blends that literally bounce back into shape, she advises, which are often those infused with Lycra. Any fabric that sags and bags can leave you looking that way, too, she says.