How is a baby actually born?
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A baby's head is that big. So how does it get out? At full term, the head is almost ten centimetres across. Yet the door it has to pass through is normally almost shut.
The trip is like a long car driving out of a narrow, winding tunnel. Start with the door. It sits at the very bottom of the womb, and it's called the cervix. For months it stays thick and tight, holding the baby safely inside.
The womb itself is one big muscle. Before pregnancy, it's about the size of a pear. By the end, the space inside has grown more than five hundred times. Near birth, this muscle starts squeezing in waves. These are contractions.
Each squeeze pushes the baby down a little, and the head presses on the door, stretching it open a little. The wider the door stretches, the more oxytocin the mother's brain releases, and the harder the womb squeezes. A push, a little wider. A little wider, a harder push.
That's how the door goes from almost shut all the way to ten centimetres. For a first baby, this part often takes most of a day. The door is open. Now the car has to steer. The mother's pelvis is a tunnel ringed with bone. Its entrance is widest side to side; its exit is widest front to back.
The baby's head is oval. It goes in facing sideways, then halfway down it turns to face the mother's back. The skull helps too. Its plates have gaps between them, so under pressure they overlap a little and the head gets narrower. That's why newborns often have slightly pointy heads that round out in a few days.
Once the head is out, the baby turns again, so the shoulders slip out one at a time, front then back. Its real name is the birth canal. The cervix is the door, the pelvis is the tunnel, and contractions are the hands pushing the car from behind. The baby is out. One breath still to go.
In the womb, the baby's lungs are full of fluid, and all the oxygen comes from the mother through the umbilical cord. The first few breaths open the lungs and push the fluid into the tissue around them. That loud first cry helps open them too. A few minutes later, the cord is clamped and cut, and the placenta follows. Only then is the trip complete.
Plenty of babies take another route: a caesarean, where a doctor opens the belly and lifts the baby straight out. One more odd thing. Human babies come out facing the mother's back, so it's hard for her to catch the baby herself. Some scientists suspect this is why, since ancient times, a woman giving birth has almost always had someone there to help.
What time were you born? Have you ever asked your mum?
A head bigger than the door
At full term, a baby’s head is almost ten centimetres across.
The door it has to pass through is normally almost shut.
The trip is like a long car driving out of a narrow, winding tunnel: the door has to open, something has to push from behind, and the car has to steer.
The door, pushed open bit by bit
The door sits at the very bottom of the womb. Its real name is the cervix. For months it stays thick and tight, holding the baby safely inside.
Near birth, the womb starts squeezing in waves. These are contractions. Each squeeze pushes the baby down a little, and the head presses on the door, stretching it a little wider.
The wider the door stretches, the more oxytocin the mother’s brain releases, and the harder the womb squeezes. A push, a little wider; a little wider, a harder push. For a first baby, this part often takes most of a day.
How the body knows it’s time is another episode: how the body knows it’s time to give birth.
The pusher is one big muscle
The womb itself is one big muscle. Before pregnancy, it’s about the size of a pear; by the end, the space inside has grown more than five hundred times. A contraction is that whole muscle squeezing at once.
The baby turns twice
The mother’s pelvis is a tunnel ringed with bone: its entrance is widest side to side, its exit widest front to back. The baby’s head is oval, so it has to turn with the tunnel.
The skull gives a little too: its plates have gaps between them, so under pressure they overlap slightly. That’s why newborns often have slightly pointy heads that round out in a few days. One of those gaps stays open for a while — the soft spot on a baby’s head.
The real names
Out — one breath to go
In the womb, the baby’s lungs are full of fluid, and all the oxygen comes from the placenta through the umbilical cord (how babies breathe in the womb).
The first few breaths open the lungs and push the fluid into the tissue around them; that loud first cry helps too. A few minutes later, the cord is clamped and cut, and the placenta follows.
Another route, and one odd thing
Plenty of babies take another route: a caesarean, where a doctor opens the belly and lifts the baby straight out. In China, about four in ten babies are born this way.
One more odd thing: human babies usually come out facing the mother’s back, so it’s hard for her to catch the baby herself. Some scientists suspect this is why, since ancient times, women giving birth have almost always had someone there to help. It’s still a hypothesis.
Every birth is different. For what to do, follow your doctor’s advice.
The baby turns.
Out it comes.
Quick check
A baby's head is almost 10 cm wide. What mainly gets it out?
Like a long car in a winding tunnel: the pushing hands (contractions) open the door (cervix), and the car (baby) steers through the pelvis.
