Inside Out: A Trimester Guide for You and Baby

What Baby Is Up To During The 1st Trimester?

In just 12 weeks, your baby goes from a bundle of cells to a tiny human.

• By week 4, their major organs are starting to form.At week 5, their heart begins to beat.
• By week 7, their limb buds appear, and the internal organs begin to develop.
• At week 8, their facial features such as ears and a small nose begin to form.
• By the end of the first trimester, your baby has fingers, toes, and a four-chambered heart. Not bad for someone smaller than a raspberry.

What Baby Is Up To During 2nd Trimester?

Your baby is getting stronger and more developed by the week:

• By week 16, they’re practising facial expressions.
• By week 17, bones are forming, and joints are more flexible.
• By week 18, they can hear your voice and respond to loud noises.
• Week 19 is all about sensory development (smell, touch, sight, hearing and taste).
• By week 20, your small sweet potato has fingerprints and hair and is starting to establish sleep-wake cycles. They’re also swallowing amniotic fluid, urinating, and maybe even sucking their thumb.

What Baby Is Up To During 3rd Trimester?

Your baby is gaining weight fast, adding fat to regulate body temperature after birth.

• By weeks 28–30, they’re blinking, grasping, hiccupping, and turning their head toward light. Their lungs are maturing, and they’re practising breathing (although they’re still surrounded by fluid.
• By weeks 31–32, their brain is developing rapidly, forming more complex neural connections. Many babies tend to turn into a head-down position around this time. You might feel more pressure in your pelvis as they drop lower, but breathing may feel a little easier.
• By weeks 33–34, their bones are hardening (except for the skull, which stays soft for delivery), and they’re continuing to gain weight.
• By weeks 35–36, their lungs are nearly ready and producing surfactant, a substance that helps them breathe after birth.
• By weeks 37–40, they’re considered full term. Their immune system is absorbing antibodies from you to help protect against infections. 

What You Might Notice

Here are a few telltale signs that labour is coming:

• Regular contractions that get longer, stronger, and closer together
• A dull backache or period-like cramps
• Your waters breaking (either a gush or a slow trickle)
• Increased pelvic pressure or the urge to poo (yes, really)

Good to know: Braxton Hicks may have kept you guessing before, but true labour contractions don’t ease with rest or hydration. They stick around and build in intensity.

What Baby Is Up To

By the time you're ready to push, your baby is lined up and doing their part to make their entrance into the world. Sure, it feels like you’re doing all the work (and fair enough), but labour really is a team effort. You push, and your baby twists, tucks, and shimmers their way out.

Stage 1: Early and Active Labour (Cervix dilates from 0 to 10 cm)

• As your contractions begin, your baby gets into position. Their head presses down on the cervix, helping it thin out (efface) and open up (dilate).
• If they’re head-down, they’ll start to tuck their chin to fit more snugly through the birth canal.
• With every contraction, they gently shift and rotate, responding to the pressure and your movements.
• They may be quiet and conserving energy, but they’re actively helping your body prepare for what’s next.

Stage 2: Pushing and Birth

• Your baby begins to descend further into the pelvis.
• They rotate again, this time to align their head and shoulders with the birth canal.
• Their skull bones, still soft and flexible, gently mould to fit through the tight space.
• As you push, they work with your contractions, inching closer to their debut.
• This stage ends with that unforgettable moment: your baby’s first breath and first cry.

Stage 3: Delivering the Placenta

• While you deliver the placenta, your baby is low-key panicking about the sudden drop in room service and letting out that glorious first cry.
• They take their first real breaths and begin using their lungs for oxygen.
• Their skin may still carry traces of vernix (that waxy coating), and their body is working to regulate temperature.
• Their circulatory system switches over from relying on the placenta to working on its own.
• They’re also beginning to bond (locking eyes, recognising your voice, and adjusting to light, sound and touch).