I've been a midwife for 9 years. I can usually tell, by the 28-week appointment, which mums are about to stop sleeping.

The pattern I couldn't ignore

Nobody warns you that the problem isn't falling asleep. It's the four hours after.

I was trained to say the standard things. Third-trimester sleep is difficult. Try to settle on your left side. Pillow between the knees. Mostly, hang in there — it's temporary.

For a few years, that's exactly what I told every woman. Then I started keeping a mental tally. Ten appointments a week, similar gestation, similar aches on paper — and without fail, they split into two groups. One group was tired but coping. The other was hollowed out by 32 weeks: back pain, hip pain, up four or five times a night, and no idea why they were so much worse off than the friend with the same due date.

It wasn't bump size. I've seen a twin pregnancy sleep better than a first-time singleton. It didn't track with the mattress, the room, or how "good a sleeper" someone had been before. It didn't track with anything I'd been trained on.

What's actually happening

It isn't that you can't sleep on your side. It's that you don't stay there.

Once I started asking about sleep position instead of sleep hours, the pattern was obvious. The women coping well went to sleep on their side and were still roughly there at 5am. The women who were wrecked started on their left, drifted onto their back somewhere around 2am, and woke with a dead lower back — over and over, without ever knowing it had happened.

There's a straightforward reason for the drift. A side-lying position in late pregnancy is unstable: the bump wants to roll forward, the top hip wants to fall inward, and there's nothing behind you. Your body solves that instability the same way it always has — by rolling flat onto the back, where the weight is finally supported. That's also the position Australian pregnancy guidance asks you to move away from from around 28 weeks, and the position that leaves the lower back and pelvis carrying the load all night.

Which means the fix was never willpower. It's a shape that makes the side comfortable enough to stay in.

That's the entire idea behind Bub's Maternity Pillow™. The wing sits behind your back so rolling flat isn't the path of least resistance, the front section takes the weight of the bump, and the length between your knees keeps the top hip from dropping and twisting the pelvis.

Why the pillow stack doesn't hold

You don't need more pillows. You need the ones you have to stop moving.

Nearly every woman I visit has already built something out of what's in the linen cupboard: one under the bump, one between the knees, one wedged behind the back, sometimes a rolled towel. It works beautifully for about twenty minutes. Then the knee pillow slides out, the back pillow migrates to the floor, and by 2am the whole arrangement is on your partner's side of the bed and you're flat on your back again.

The reason is simple — three separate objects can't hold a position when the person on top of them moves. Bub's is one connected shape, so the bump support, the wing and the knee section can't drift apart from each other. Supported, not stacked. That's the difference that mattered every time I compared the two.

Adjusts to you, not the other way around

The right length matters more than anyone tells you.

A pillow that's too short leaves your knees unsupported; too long and it takes over the bed and pushes your partner out. Bub's is adjustable in length, so a 5'2" first-timer and a 5'10" mum of three can both get the knee section landing where it should.

It comes in cream, turquoise and peach, and the cover comes off and goes straight in the wash — which will matter to you far more at 34 weeks than any spec sheet lets on.

The honest use list

What women actually use it for, week to week.

• Holding a comfortable left-side position overnight from the second trimester on
• Taking the bump's weight off the lower back, which is where most third-trimester ache lives
• Keeping the top knee level so the pelvis isn't twisted for eight hours
• Propping yourself upright in bed when reflux or breathlessness makes lying down unpleasant
• After birth: support under your arms while feeding, so your shoulders aren't doing the work
• After a caesarean: something to brace against when you're getting in and out of bed

Six things. All of them ordinary. That list is shorter than what some competitors promise, and every line on it is honest.

The part nobody plans for

It doesn't become useless the day the baby arrives.

Most pregnancy purchases have a hard expiry date. This one doesn't. In the first weeks after birth, the women I visit are feeding eight to twelve times a day, mostly sitting up in bed at 3am, holding the entire weight of a newborn on two forearms and a set of already-wrecked shoulders.

The same pillow goes around the waist or under the arms and takes that weight instead. A partner can set it up. A grandparent can. After a caesarean it's also the thing you brace against getting out of bed, which is a small mercy that nobody mentions at the hospital.

What it costs

Less than most of what ends up unused in the nursery.

I've walked into a lot of nurseries with a wipe warmer nobody plugs in, a $200 bouncer used exactly once, and a steriliser replaced by a saucepan of boiling water by week two.

The pillow is $70.95 right now, down from $105.95. Free delivery anywhere in Australia, Afterpay if you'd rather split it, and 30 days to decide whether it earns its place in the bed. If it doesn't, send it back for a refund.

Before you order

The questions we get most.