You might hear different things about when a baby is ready to be born, or when he can safely be born even if he’s premature.
It can be a worrying time for some mothers during pregnancy.
Wondering about when your baby can be born safely can be a source of concern.
This might be the case for you – especially if you’ve already lost a baby through miscarriage or stillbirth. This is also a common worry for many mothers who wonder if they’ll make it to their pregnancy estimated due date.
It can dull the excitement of choosing a name, decorating the nursery and enjoying your pregnancy.
So when is a baby fully formed and ready to be born? Let’s take a look to find out more about fetal development and reduce some of those worries you might have during pregnancy.
When does an embryo become a fetus?
It’s important to look first at the scientific terms for a baby during pregnancy.
These are the biological terms and the stages of fetal development:
- Zygote: an egg that has been fertilized by a sperm
- Blastocyst: a zygote that has begun to divide and grow
- Embryo: the zygote becomes an embryo around 5 weeks of pregnancy, when various systems of the body begin to form
- Fetus: around 8 weeks pregnancy, when the heart has begun beating, your baby will be considered to be a fetus
Of course, these are the scientific terms, but you’re more likely to refer to him (or her) as your baby during your pregnancy.
As soon as the sperm and egg join, and the fertilized egg implants into the wall of the uterus, your baby has started on his journey of growth and you’ve started your amazing journey of pregnancy.
Fetal development stages
Your baby goes through three stages of fetal development as they head towards their due date.
The first is the two weeks after conception, called the germinal stage as the fertilized egg travels down the Fallopian tube to the uterus and implants. This is the very early stages of pregnancy, before you find out that you’re having a baby. Your next expected period will be missed and you’re likely to take a test to find out if you’re pregnant. Find out more in How Early Can You Take A Pregnancy Test?
Then comes the embryonic stage, which is week 3 to 8. This is the stage of pregnancy that’s very exciting but also when you’re likely to start feeling the effects of those pregnancy hormones. Pregnancy symptoms usually start around weeks 6 to 8 but some women feel them earlier and others later. Find out what signs of pregnancy you can look forward to in Pregnancy Symptoms – 17 Early Signs You Might Be Pregnant.
The time from pregnancy week 8 until birth is the fetal stage – the third and final stage of fetal development for your baby.
BellyBelly’s pregnancy week by week series goes into more detail about the way your baby develops as your pregnancy progresses.
How long does it take for a baby to form in your stomach?
A common misconception is that fetal development happens in the woman’s stomach.
The mother’s stomach is only for the digestion of food.
If you hear someone saying a baby is in the stomach, they’re likely to be referring to the belly area.
The egg is usually fertilized by the sperm in the Fallopian tube then travels to the uterus.
The baby grows in the womb, otherwise known as the uterus. Pregnancy only happens in this organ.
It’s near the stomach, and it can certainly feel like the baby is in there when it’s causing digestive problems or when the baby is big enough to push against it with their arms and legs!
What is the first organ to form in the womb?
The first thing you’re likely to notice in the development of your baby is his heart, when you see it on the ultrasound or hear it beating on the doppler.
A doppler is an instrument your health care provider uses to listen to the heartbeat of your baby.
This is one of the things mothers get the most excited about in early pregnancy.
It can also be one of the things they worry about the most during pregnancy. Seeing or hearing there’s a heartbeat is crucial to knowing you have a healthy baby.
What is the last organ to develop in a fetus?
By the time you reach the third trimester, your baby’s brain will be completely formed but the inner neural pathways and connections will still be wiring up.
When is a baby’s brain fully developed in the womb?
In terms of fetal development, your baby’s brain actually keeps growing after birth! An amazing fact about the human brain is it continues to develop after the birth of your baby, even well into early adulthood. After birth, many of the ways you respond to your baby may help his brain development.
Check out The Fourth Trimester – 8 Ways To Create One For Your Baby for more information about responding to your baby.
When is baby’s head fully formed?
Your baby’s head will begin to form quite early but won’t be fully formed until around 24 weeks. At this stage, they will have the face of a newborn baby. Their eyes will be quite prominent as their cheeks haven’t yet developed any fat. The eyelids will stay fused closed until about 25 weeks pregnant, when they will open.
Which trimester is the most critical?
The first trimester is when all the structural and organ development of your baby is underway. In the first 12 weeks of pregnancy, a developing baby is the most vulnerable to any harmful influences.
It’s also the time when birth defects and miscarriages are most likely to happen.
During this stage of fetal development, getting plenty of high-quality nutrition helps your body support the amazing development going on inside.
Not drinking alcohol, and avoiding tobacco smoke and harmful substances will go a long way to protecting your baby in this critical period of fetal development. Your healthcare provider can advise you on ways to have a healthy pregnancy, especially if you drank alcohol before you knew you were pregnant.
Find out more in What To Avoid During The First Trimester.
Which trimester does the baby grow the most?
By the time you get to the second trimester, your baby’s growth is really accelerating. It’s also the time when the digestive system, including organs such as the intestines, liver, gallbladder, and pancreas becomes fully formed.
The central nervous system is developing apace, triggering your baby’s movements and other antics in there. During your 20 week ultrasound, you might even get to see those arms and legs waving around!
During this stage of pregnancy, you’ll be gaining more weight, to keep up with your baby’s demands on your body.
By this stage of pregnancy your baby is about the size of a banana. They weigh about 10.2 ounces (230 grams) and measure about 6.5 inches (17cms) from crown to rump. After 20 weeks, measurements will be from baby’s head to their toes as they keep developing.
Exercise and a healthy diet are key components of how you can support your body and your baby’s health too. Talk to your healthcare provider for suggestions on how to stay healthy.
Is baby fully developed at 20 weeks?
At 20 weeks you’re halfway through your pregnancy, although remember 40 weeks is the average length of gestation.
Your baby at 20 weeks pregnant is still working on development of organs and their lungs aren’t close to being fully formed. They’re starting to develop vernix caseosa to protect their skin from the effects of being in amniotic fluid for another 20 weeks.
It’s not for about four more weeks that your baby would be considered developed enough to survive outside the uterus. Even then, your baby isn’t fully formed as their lungs wouldn’t be able to manage to breathe on their own. So while you might be able to feel their movements as they try out their arms and legs, your baby needs more time to develop.
Read more about this stage of pregnancy in 20 Weeks Pregnant | Belly, Ultrasound and Symptoms.
At what week can a baby survive outside the womb?
Babies born before 37 weeks are considered premature. Babies who are born after 37 weeks are considered full term.
Advancements in medical technology have meant a baby born very early have a much better chance of survival than they did even a few decades ago.
Today, doctors consider 24 weeks as the earliest a baby may be able to survive outside the womb. Babies who are born earlier than this can’t survive as their lungs and vital organs are underdeveloped.
A baby born at 24 weeks gestation is still very premature and will need a lot of intensive care support to avoid complications due to prematurity. Your health care provider would try to keep your baby in the womb for as long as possible if labor threatened at this stage.
For more information be sure to read Premature Babies – What To Expect Week By Week.
Is baby fully developed at 37 weeks?
Your baby is considered fully developed or full term from 37 weeks by medical terms. However, it’s worth bearing in mind that not all babies are born in the weeks leading up to 40 weeks gestation.
Some babies aren’t born until the weeks after their estimated due date. As babies initiate the labor process, this leads us to understand there is still fetal development taking place.
A baby’s ability to breathe outside the womb is a big part of when labor is initiated. The estimated due date you’re given is only an idea of when your baby will be ready for birth.
That’s why it’s so important to wait for labor to start on its own. Your baby is likely to be fully developed at 37 weeks and if labor starts spontaneously then fantastic!
You might like to read more in What Causes Labor To Start?
In which week is delivery safe?
Babies are considered full term from 37 weeks. A baby’s organs are fully formed by now and most of their body systems are able to cope with life outside the womb.
Although the lungs first start to develop at about 6 weeks, it’s not until 35 weeks your baby’s lungs are putting their ‘final touches’ on, preparing to breathe for the first time.
The development of your baby is a delicate process.
Everything is happening in there so quickly – you’re growing a whole new human being!
Be easy on your body and mind, so your baby can stay in there for as long as he needs!