Pregnancy, Sleep, and Your Baby’s Emerging Circadian Rhythm

As a Child Sleep Consultant, one of the most common questions I hear from expectant parents is: “Does my baby have a sleep rhythm before birth?” and “Why is it so hard to sleep while I’m pregnant?” The short answer is—yes, your baby’s body clock starts forming in the womb, and your changing hormones play a big role in both their rhythms and your own sleep. Let’s dive in.

Why Sleep Feels So Hard During Pregnancy

If you’re pregnant and struggling with sleep, you are far from alone. Pregnancy brings big physical and hormonal shifts that can affect your rest:

• Progesterone rises to support your pregnancy, but it can also make you feel more drowsy during the day while leaving you restless at night.

• Oestrogen increases circulation, sometimes causing nasal congestion or night sweats that interrupt sleep.

• Physical changes like a growing belly, heartburn, or frequent bathroom trips also make it harder to stay comfortable.

Your body is working incredibly hard, and those sleep challenges are a normal part of preparing for your baby.

Your Baby’s Sleep Rhythm Starts in the Womb

Here’s the fascinating part: while you’re adjusting to disrupted sleep, your baby is beginning to form their own circadian rhythm—their internal body clock that regulates sleep and wake cycles.

• Around the second trimester, your baby starts responding to maternal cues such as melatonin, the hormone that signals darkness and sleep.

• Melatonin crosses the placenta, so when your levels rise in the evening, your baby gets a hormonal “signal” that it’s nighttime.

• By the third trimester, babies start to show more distinct patterns of activity and rest, influenced by your sleep-wake rhythm, meals, and movement.

This means that long before your baby is born, they’re already being gently guided by your hormonal clock.

How Hormones Help Shape Baby’s Clock

• Melatonin: Your nightly surge of melatonin helps set your baby’s awareness of day vs. night.

• Cortisol: Levels naturally rise in the morning, and these fluctuations also pass through the placenta, giving your baby cues about when it’s time to be more alert.

• Light Exposure: While your baby doesn’t “see” light the way you do, your light–dark cycles influence your hormone production, which in turn influences theirs.

  
  

In other words: your body acts like your baby’s very first sleep teacher!

Sleep Tips for Expectant Parents

While you can’t control every pregnancy symptom, here are some gentle strategies that may help you rest:

1. Follow a calming bedtime routine – wind down with dim lights, a warm shower, or relaxation techniques.

2. Prioritize sleep position – many parents find side-sleeping (especially on the left) more comfortable and supportive.

3. Use pillows for support – between your knees, behind your back, and under your belly can relieve pressure.

4. Keep your bedroom cool and dark – this supports your natural melatonin production.

5. Practice mindful rest – even if you can’t sleep, lying down and focusing on your breath still helps your body restore.

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A Gentle Reminder

Your pregnancy sleep won’t be perfect, and that’s okay. Think of this season as your body’s way of slowly preparing you for the unpredictable rhythms of early parenthood. And remember, your hormones are already helping your baby develop the foundations of their circadian rhythm—long before you’re reading bedtime stories or rocking them to sleep.

Want Support From the Very Beginning?

If you’d love to feel confident about sleep from day one, my Newborn Plan is designed to guide you through those early weeks with practical, gentle strategies that support healthy sleep habits right from the start. You don’t have to figure it all out alone—I’m here to help you and your baby get the best rest possible.