Underwear for Pregnancy: What to Wear Each Trimester

By Sustainable Underwear Australia | Published: 2026-10-13

Category: How-to Guides

A trimester-by-trimester guide to pregnancy underwear, from early comfort tweaks to nursing-ready bras and postpartum recovery.

Quick answer

Start with soft, stretchy briefs that sit under your bump in the first trimester, then add full-bump coverage and a properly fitted maternity bra as your ribcage and breasts change. In the third trimester, prioritise a bra that converts for feeding and briefs that stay comfortable after birth. Replace anything that digs, rolls, or leaves marks, and don't wait until a size feels tight before sizing up.

First trimester: comfort tweaks before you need maternity wear

Your body may not look different yet, but bloating, breast tenderness, and a growing ribcage often show up early. This is the trimester to audit what you already own. Anything with a firm waistband, a deep gusset seam, or a wire that presses on breast tissue will become uncomfortable fast. Switch to soft, seamless briefs and a wireless bra now, and keep one or two old favourites for days when you want extra support.

You don't need a full maternity wardrobe in weeks 1–12. Buy two or three pairs of stretchy briefs and one wireless bra in your current size, then reassess at the end of the trimester. If you're already feeling pressure across your ribs, go up one band size rather than a cup size first.

Second trimester: fit your bump and your band

From around week 14, your uterus rises out of the pelvis and low-rise briefs start to sit awkwardly. Switch to briefs with a soft, wide front panel that sits under or over the bump without digging. Look for a gusset that stays flat when you move, and avoid heavy elastic that leaves red marks after an hour.

Your bra band is the measurement most likely to change now. Ribcage expansion can add a full band size even if your cup size hasn't shifted. Re-measure every four to six weeks, and use the loosest hook when a bra is new so you have room to tighten it later. If the band rides up at the back, it's too loose; if the cups crease at the top, the cup is likely too big or the band is too small.

Third trimester: prepare for feeding and recovery

By the third trimester, you're buying for two phases: the last weeks of pregnancy and the first months of feeding. A drop-cup bra lets you feed one-handed, which matters when you're holding a baby with the other arm. A bra that converts to a regular bra or a racerback gives you more wear after your feeding journey ends, so it isn't a short-term purchase.

For briefs, choose a style that won't press on a caesarean scar if that's a possibility, and size for the larger of your pre-birth and postpartum shape. Many people find they need one size up in the days after birth before settling back down. Wash new items before your due date so they're ready in your hospital bag.

Your trimester-by-trimester action steps

Step 1: Audit your current underwear drawer: Set aside anything with a firm waistband, a wire that presses on breast tissue, or a seam that rubs. Keep only soft, stretchy pieces that stay flat when you sit, stand, and bend. Checkpoint: if you can see red marks after one hour, it's out.
Step 2: Buy two or three stretchy briefs in your current size: Choose low-rise or under-bump styles with a wide, soft front panel. Don't buy a full set yet; your shape will change again in the next trimester. Checkpoint: the gusset should lie flat with no twisting when you walk.
Step 3: Re-measure your bra band every four to six weeks: Measure snugly around your ribcage, then add the band size. Use the loosest hook on a new bra so you can tighten it as the band relaxes. Checkpoint: the band should stay level at the back, not ride up.
Step 4: Switch to a maternity bra with drop cups by the third trimester: Look for one-handed feeding clips and a non-wire design you can sleep in. A convertible style that becomes a regular or racerback bra extends its life beyond feeding. Checkpoint: you should be able to open and close the cup with one hand while holding a pillow.
Step 5: Size for postpartum, not just your due date: Buy briefs that fit the larger of your late-pregnancy and early-postpartum shape. If you're planning a caesarean, choose a style that sits away from the scar line. Checkpoint: wash everything before your due date and pack two bras in your hospital bag.

Maternity bras that adapt as you do

Recycled Maternity Bra - Cranberry: 4-in-1 design: non-wire pregnancy bra, drop-cup feeding bra, converts to a regular bra, and converts to a racerback sports bra with the clips. One bra covers pregnancy, feeding, everyday wear, and light activity, so you're not buying a single-use item.
Recycled Maternity Bra - Black: Non-wire construction comfortable enough to wear all day and sleep in, with a drop cup for one-handed feeding. Useful for night feeds and long days when you don't want to change bras between sleeping and feeding.