If you’re in the market for maternity lingerie, you have almost certainly mastered the art of procreation. By comparison, choosing maternity lingerie for her should be easy. Still, like procreation, there are some things you’ll probably want to know first.

The first thing you need to know is this: her body changes dramatically when a baby hijacks it. Her existing clothes won’t do the trick. For one thing, things swell. Not just her belly, but other things too. Her old lingerie isn’t likely to even fit. There are more issues than just fit. She won’t want bras with wires in them—they can inhibit milk production. Stitching or seams across the nipples can irritate her nipples; the further along she gets, the more sensitive they become. She’ll also need quick release clips. Once she has the baby, that is—for breastfeeding.

Size Matters

The biggest challenge in choosing maternity lingerie is, quite frankly, bigness. If the lingerie is too small, besides being uncomfortable it will ding her self esteem because it’ll make her feel fat. If you are buying lingerie for someone else, and it’s too big, I think you can figure out yourself why that’s sending the wrong message and might get you in trouble. The place to start is to look at what she already has. Notice what fits well. Take note of the size.

With bra sizes, the number is her rib-cage circumference, or ‘under-bust’, and the letter is her breast or ‘cup’ size. Bear in mind that when a woman is pregnant she will usually increase at by at least one cup size. If you find all this confusing you can just take some of her current lingerie to the store with you. You could also ask a close female friend of hers to help, but be warned that, if it’s supposed to be a surprise, women suck at keeping secrets.

What a Girl Wants Vs. What You Want For Her

Men and women both appreciate fancy lingerie—but for different reasons. Women like how it makes them feel about themselves, how it makes them feel attractive. Men, of course, like… Well, that gets back to mastering the art of procreation, doesn’t it.

If you’re a man buying lingerie for a woman, bear in mind that your reasons for wanting her to have lingerie may differ somewhat from hers, you’ll need to use your brain as well as your … instincts, in order to make both of you happy (the woman in question and you yourself, not you and your… instincts.) In other words, think about what colors and styles she likes. It’s risky buying colors you’ve never seen her wear. If she doesn’t wear thongs, think twice about buying her ‘butt floss’ no matter how hot you think she’ll look in it. Better, perhaps, to stick closer to her normal style, be it bikini panties or some sort of fancy French knickers.

Also, she will most likely want a selection of nighties, camisoles and pajamas, not just the basic brand and panties combo.