Why Your Newborn Jerks Awake The Moment You Put Them Down

You spend twenty minutes getting them to sleep. You lower them into the cot. Their arms fly out, they gasp, and they’re awake and furious.

That’s the Moro reflex, and it isn’t your technique. It’s a reflex every healthy newborn is born with, and its presence is a sign the nervous system is working properly.

Putting them down without setting it off

The trigger is the sensation of falling, so the technique is about removing that sensation, not about being quiet.

1. Go bottom first, not head first. Lower their bottom to the mattress, then their back, then last of all their head. Head-first is what feels like falling.
2. Stay bent over them for a few seconds after they’re down, with a hand resting on their chest or tummy. Don’t stand up straight immediately. That removes the pressure and the warmth at once, and that’s usually the moment it goes wrong.
3. Take your hand away last, and slowly. Lift one finger at a time if you have to.
4. Warm the mattress: a hand on the sheet for a minute beforehand. Cold against the back is a common trigger.
5. Wait until they’re deeply asleep. Limp arms, slack fingers, no flicker when you lift an arm slightly. Putting down a lightly-asleep baby rarely works.
6. Don’t tiptoe. A little steady background noise is better than a silent room, in which every small sound is a sudden one.

Swaddling, and when to stop

Swaddling works because it stops the arms flying out, and most parents find it manageable: 70% of our readers said they found swaddling easy (714 votes).

But one rule counts for more than the technique, and our own readers’ answers suggest it isn’t widely known.

Why it matters: a swaddled baby who rolls onto their front can’t push up on their arms or turn their head clear. The thing that makes swaddling effective is exactly what makes it dangerous once rolling starts. The signs come before the first successful roll: rolling to the side, rocking, lifting the shoulders, more vigorous kicking. Stop at the first sign, not the first roll.

The rest of safe swaddling:

• Firm across the chest, loose around the hips. Legs need to bend up and out; tight straight legs are linked to hip dysplasia.
• On the back, always. A swaddled baby must never be placed on their side or front.
• Nothing near the face, and no loose fabric in the cot.
• Watch for overheating: a real concern in Singapore. One light layer under the swaddle, and check the back of the neck, not the hands.
• A transition sack with the arms out is the usual next step, and it makes the change much easier than going straight to nothing.

Coming out of the swaddle

The startle reflex will still be there when you stop swaddling, so the first few nights are hard. Two approaches, both fine:

• One arm out for a few nights, then the other, then the sack.
• Straight into an arms-out sleeping bag and ride out three or four unsettled nights.

Either way it passes, and the reflex itself is fading by then anyway.

When to mention it to a doctor

• Still clearly present after six months
• Only on one side, or noticeably stronger on one side. This is checked because it can indicate a birth injury to the shoulder or arm
• Absent altogether in a newborn
• Movements that come in repeated clusters without any trigger, or a stiffening that looks different from the usual fling-and-gather. Startles are always triggered by something and are brief, and anything that doesn’t fit that pattern should be shown to a doctor. Film it on your phone; a video is worth more than a description.

Frequently asked questions

Why does my baby jerk awake when I put them down?

It’s the Moro reflex. The sensation of being lowered is read as falling, and the baby flings both arms out and then draws them in, often waking themselves. Every healthy newborn has it, and it’s a sign the nervous system is working properly.

When does the startle reflex go away?

It starts fading from around three months and is usually gone by five to six months. If it’s still clearly present after six months, mention it at your next check-up.

How do I put my baby down without waking them?

Bottom first, then back, then head. Head-first is what feels like falling. Stay bent over them with a hand on their chest for several seconds after they’re down, then remove your hand slowly. Warm the mattress with your hand first, and wait until they’re deeply asleep, with limp arms and slack fingers.

When should I stop swaddling?

At the first signs of rolling, which for many babies is around two to three months and often earlier than parents expect: rolling to the side, rocking, lifting the shoulders. A swaddled baby who rolls onto their front can’t push up or turn their head clear. Half our readers stopped at three months or later, which is later than the guidance.

Is swaddling safe?

Yes, done correctly and stopped in time. Firm across the chest and loose around the hips so the legs can bend up and out, always on the back, nothing near the face, and watch for overheating: one light layer underneath, and check the back of the neck, not the hands.

Should I worry about my baby’s startles?

Not normally. Show a doctor if the reflex appears on one side only, is absent in a newborn, is still strong after six months, or if you see repeated clusters of movement with no trigger at all. Startles are always triggered and brief; film anything that doesn’t fit that pattern.

What to remember

The jerk is the Moro reflex, it’s a good sign, and it fades by about six months.

Put them down bottom-first and keep a hand on their chest for a few seconds before you stand up. That single change fixes it for most people.

Swaddle if it helps, and stop at the first signs of rolling, not the first roll.

Read next

• Should your child’s bedroom door be open or closed at night?
• Developmental red flags: what to watch for

This article is general information and not a substitute for medical advice. If you’ve concerns about your baby’s movements or development, speak to your doctor or polyclinic.