Your twins were sleeping in decent stretches. Around four months it fell apart - and now one wakes, cries, and takes the other one with them.

Everything written about the 4 month regression assumes you have one baby. The advice is not wrong, it is just missing the part that is actually breaking you: there are two of them, and they are no longer in sync.

What's actually happening

At around four months, baby sleep permanently changes. Newborns drop straight into deep sleep. From about this age they start cycling through lighter and deeper stages like adults do - which means they surface every 45 minutes or so and have to get back to sleep.

That is why it is not really a "regression." Nothing went backwards. Their sleep matured, and now every time they surface they need to fall asleep again - and if they only ever fall asleep while being fed or rocked, they will need you every single time.

It usually shows up as:

  • Short naps (30-45 minutes, on the dot)
  • Waking every 1-2 hours at night, when they used to do longer stretches
  • Fighting sleep they used to fall into easily
  • Suddenly hungrier - the extra wakes are real, so are some of the feeds

It typically lasts two to six weeks. That is the honest range. With twins it can feel longer because you are rarely getting both babies through it at once.

The part nobody writes about: they wake each other

This is the twin-specific problem, and it is the one that decides whether you sleep.

Should you separate them? For the regression period, a lot of twin parents temporarily split them at night, then bring them back together once things settle. It is not a failure and it is usually not permanent - you are getting through a phase, not making a lifelong decision. Do what gets the most total sleep into the house.

If you keep them together: white noise genuinely helps here - it blurs the edge of a sibling's cry so it is less likely to pull the other one all the way awake. It is also worth knowing that twins habituate to each other's noise surprisingly well. Plenty of twin parents find the "she'll wake her sister" fear is worse than the reality.

Do not rush in. If one wakes and grumbles, give it a minute before you go in. Half the time they resettle and the other baby never surfaces. Charging in with the light on wakes both.

Getting them back on one schedule

During the regression, twins drift apart - one starts napping late, the other's bedtime slides, and within a week you have two schedules and no gaps for yourself. Pulling them back together is the single highest-value thing you can do.

Wake them together. If one wakes from a nap, wake the other within about 15-20 minutes. This is the lever. It feels brutal to wake a sleeping baby - do it anyway. Everything downstream (feeds, next nap, bedtime) re-aligns from that one decision.

Feed them together. Once one is eating, feed the other, even if they would have waited another 20 minutes.

Same bedtime routine, same time, both babies. Even if one seems less ready.

Watch wake windows, not the clock. Around four months most babies manage roughly 1.5-2.5 hours awake between sleeps. Overtired babies fight sleep harder and wake more - which with twins doubles instantly. If one twin's window is consistently shorter, that is real; give that baby the earlier nap and pull the other in.

What to actually do at night

Put them down drowsy but awake, at least once a day. Start with the easiest sleep of the day - usually bedtime. If a baby can get themselves from awake to asleep once, they can do it at 2am. With twins, start with whichever baby finds it easier; do not take on both at once.

Feed the wakes that are real. Four-month-olds do genuinely feed at night. You are not trying to eliminate feeds here - you are trying to stop being the only way they fall asleep.

Split the night with your partner. Not alternating babies - alternating shifts. One parent covers both babies until 2am, the other takes both after. Two people getting one solid block each beats four people-halves of broken sleep.

Log it, or you will lose the thread. Two babies, two patterns, several wakes a night, on no sleep - you cannot hold that in your head. A twin baby tracker shows both babies side by side, so the parent who can see "baby A is waking at 1am and 4am, baby B only at 3am" is the parent who fixes it in a week instead of a month.

When to call the pediatrician

The regression is normal. These are not, and are worth a call:

  • A baby who is not gaining weight, or has fewer wet nappies than usual
  • Waking that seems driven by pain rather than sleep
  • Sudden change in one twin but not the other, with other symptoms
  • Anything where your gut says something is wrong

You know your babies. If it does not feel like a sleep phase, get it checked.

The honest summary

It ends. Two to six weeks, usually. The two things that shorten it with twins: keep their schedules glued together by waking them at the same time, and let each baby practise falling asleep on their own once a day.

Everything else is survival, and survival counts.

This article is general information for parents, not medical advice. For anything about your babies' health, weight or feeding, talk to your pediatrician or health visitor.