You’re home from hospital. Your baby is finally here. The past couple of days have been a rollercoaster of massive highs—like, how on earth did I grow something so perfect?—and sending out the baby announcement on socials with an outpouring of “OMG, congratulations!”...
...to the really low lows (feeling like your vagina’s been kicked by someone in steel-capped boots and your poor nipples have had a fight with a cheese grater). Oh hail the Silver cups!'
There are still congratulatory cards half-opened on the kitchen bench, a cold cup of tea in every room, and that hospital bag? Still sitting in the hallway—half unpacked, quietly reminding you that you haven’t had a second to breathe.
Somewhere between the tears (theirs and yours), the nappies, and maybe two hours of sleep, you're wondering: Is this normal?
First of all: yes. Probably.
And also—no one really tells you how big, beautiful, and utterly disorienting these first six weeks can be.
So let’s walk through it together.
No one told you about this part, right?
The fourth trimester isn’t something you’ll find on a hospital discharge summary, but it’s just as real—and just as important. It refers to the first 12 weeks after birth: when your baby is adjusting to life outside the womb, and you’re adjusting to life as a mother.
As a midwife, I honestly can’t count how many times I’ve heard new parents ask, “But… is that normal?” And the truth is, the fourth trimester is the chapter where so much of what’s normal feels completely disorienting.
Yes, awareness is growing—which is amazing—but we still have a long way to go in helping parents actually understand this stage. Because this is the part that leaves many of us feeling rattled, overwhelmed, and way out of our depth.
Fourth Trimester
WELCOME TO THE
Fourth Trimester
Why does the
exist?
Why didn’t all this development happen while the baby was still inside?
From an evolutionary perspective, as humans began walking upright, our pelvises adapted to allow for bipedal movement—which meant narrowing in shape. The result? A trade-off: while our brains were growing larger, the birth canal was getting smaller. Something had to give.
That “something” was the length of gestation.
At birth, a human baby’s brain is only about 25% of its adult size. By the time your child turns three, it will be closer to 80–90%. The reason we don’t grow them fully finished in the womb? Quite simply—your pelvis couldn’t birth a bigger head.
So, in a very real sense, we birth our babies prematurely compared to other mammals.
In the animal kingdom, mammals fall into two general categories:
altricial (born undercooked) and precocial (born ready to run).
Let’s break it down:
Altricial mammals:
Think puppies, kittens, baby mice.
They're born blind, wobbly, completely helpless.
They stay in the nest, feed infrequently on milk that’s really high in fat, and rely on mum popping back between foraging trips (usually 2-4 times a day)
Precocial mammals:
Think lambs, foals, baby monkeys.
They’re born way more developed—eyes open, legs working, able to cling or walk soon after birth.
They stay with mum, feed frequently—sometimes as often as every hour—and their milk is high in sugar and low in fat.
early?
So… are our babies born
Or just kind of
half baked?
Biologically, we lean toward the precocial group. Our babies:
Can see, hear, cry, and suck
Have functioning internal and sensory systems
Need to feed frequently
Are born one at a time (usually)
Thrive on being carried and kept close
But unlike other precocial mammals, our babies are neurologically incomplete at birth.
They have the grasp reflex—but not the strength to cling.
They need to be carried because they can’t yet follow.
Compared to apes, who are born with 50% of their brain developed, our babies are only at 25%. Which means they’re still cooking. Just outside the womb.
This is why human babies are often described as “extero-gestated”—a fancy way of saying they finish their gestation on the outside.
For the first three months after birth, your baby is still adjusting to life earth-side.
They need what the womb gave them:
Warmth
Movement
Constant contact
Frequent feeds
A consistent caregiver nearby for comfort and regulation
That’s why this time is called the fourth trimester. It’s not a throwaway phrase—it’s a crucial developmental window, just as important as pregnancy itself.
So if your baby only sleeps on you, wants to feed all the time, and cries every time you put them down?
You’re not creating “bad habits.”
You’re responding to biology.
And you’re doing it right.
human babies
so where do
fit?
Here’s the truth no one puts on the baby shower bingo card:
Your baby is not a robot. They’re a baby. A very new one.
These are the behaviours that are biologically normal—and expected—in the early weeks:
Feeding constantly, sometimes every 45 minutes (especially in the evenings)
Waking frequently, because their circadian rhythm isn’t developed yet.
Wanting to be held most of the day
Crying when put down—because being alone doesn’t feel safe yet.
Short naps, contact naps, unpredictable naps—it’s all part of the process.
This doesn’t mean it’s not hard. It is.
But it’s not broken. It doesn’t need fixing.
It needs understanding, support, and a whole lot of grace.
If you’d like to go deeper into this fourth trimester chapter—what’s really happening for your baby, how sleep evolves, and how you can gently support the transition from womb to world—you’ll find everything in my Newborn Sleep Guide: Womb to World.
It’s there when you’re ready.
