Ten weeks old fetus
Pregnancy at week 10 | Pregnancy Birth and Baby
Pregnancy at week 10 | Pregnancy Birth and Baby beginning of content4-minute read
Listen
Your baby
From 10 weeks, your baby is called a fetus. They are about 3.5cm long – around the size of a prune – and weight about 8g. The tadpole-like tail has disappeared.
All of the organs have formed but they aren’t working yet. The ears are developing and the nostrils are in place above the upper lip. The jaw bones already include all the milk teeth.
The baby has internal sex organs, their ovaries or testicles, but the external sex organs still haven’t developed. The brain is active and has brain waves. The heart has 4 separate chambers and is beating at about 180 beats per minute, 3 times faster than an adult heart.
The arms and legs have grown longer, and the baby has tiny fingers and toes. Their ankles, wrists, knees and elbows are forming.
Your baby at 10 weeks
Length: | 3.5cm |
Weight: | 8g |
Your body
Your womb (uterus) is now about the size of an orange. You may find your clothes are tighter and your stomach may be sticking out, but this can be due to changes in your bowel rather than your pregnancy.
Many women feel vulnerable and emotional when they are pregnant. This is completely normal. You may also be more hungry than usual. Try not to fill yourself up with unhealthy food – choose nutritious snacks as part of a healthy diet while you’re pregnant.
Things to remember
You may have already had an ultrasound scan to confirm your due date, but a dating scan is normally done at around 10 weeks.
From 10 weeks you can start thinking about prenatal screening. One screening test you can have now is a non-invasive prenatal test, or NIPT, to screen for Down syndrome and certain other abnormalities in the baby. This is a simple, very accurate blood test, but it’s quite expensive and it’s not for everyone. Most women who want to screen for Down syndrome have combined first trimester screening a little later in the pregnancy.
You do not have to have screening. It depends on your age, history and unique circumstances. Talk to your doctor or genetic counsellor about the best screening tests for you.
Read next
Your pregnancy at 11 weeks
Learn about your pregnancy journey and what is happening to you and your baby.
Speak to a maternal child health nurse
Call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 or video call. Available 7am to midnight (AET), 7 days a week.
Sources:
Raising Children Network (Pregnancy week-by-week), Better Health Channel (Pregnancy - week by week), Women's and Children's Health Network (The first 3 months of pregnancy: the first trimester)Learn more here about the development and quality assurance of healthdirect content.
Last reviewed: August 2020
Back To Top
Related pages
- Pregnancy week-by-week
Need further advice or guidance from our maternal child health nurses?
1800 882 436
Video call
- Contact us
- About us
- A-Z topics
- Symptom Checker
- Service Finder
- Linking to us
- Information partners
- Terms of use
- Privacy
Pregnancy, Birth and Baby is funded by the Australian Government and operated by Healthdirect Australia.
Pregnancy, Birth and Baby is provided on behalf of the Department of Health
Pregnancy, Birth and Baby’s information and advice are developed and managed within a rigorous clinical governance framework. This website is certified by the Health On The Net (HON) foundation, the standard for trustworthy health information.
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
This information is for your general information and use only and is not intended to be used as medical advice and should not be used to diagnose, treat, cure or prevent any medical condition, nor should it be used for therapeutic purposes.
The information is not a substitute for independent professional advice and should not be used as an alternative to professional health care. If you have a particular medical problem, please consult a healthcare professional.
Except as permitted under the Copyright Act 1968, this publication or any part of it may not be reproduced, altered, adapted, stored and/or distributed in any form or by any means without the prior written permission of Healthdirect Australia.
Support this browser is being discontinued for Pregnancy, Birth and Baby
Support for this browser is being discontinued for this site
- Internet Explorer 11 and lower
We currently support Microsoft Edge, Chrome, Firefox and Safari. For more information, please visit the links below:
- Chrome by Google
- Firefox by Mozilla
- Microsoft Edge
- Safari by Apple
You are welcome to continue browsing this site with this browser. Some features, tools or interaction may not work correctly.
10 Weeks Pregnant: Symptoms and Baby Development
You’ve made it to 10 weeks pregnant, and that means you’re nearly at the end of your first trimester—time flies! Some of your pregnancy symptoms might be starting to subside, while others might be right around the corner. We’ve got more information about what to expect at 10 weeks pregnant in terms of signs and symptoms, plus things to think about and questions your healthcare provider can answer.
Highlights at 10 Weeks Pregnant
Below we’ve highlighted some of the ways your baby is growing and changing, and how you might be feeling at 10 weeks pregnant:
Your little one is starting to look more and more like a baby, with a rounder head and lots of little developments, like eyes, fingers, toes, and tooth buds.
With internal organs in place, your little one is just about 1 inch long.
Though pregnancy symptoms might be at their worst this week, know they’ll soon start to ease.
Since your belly bump might start to show in the coming weeks, now is a good time to consider starting a baby bump photo series!
10 Weeks Pregnant: Your Baby's Development
Your baby is making some big strides this week! Here are some of the exciting developmental steps happening inside your belly:
That little head is taking on a rounder, more human shape, and by now all the internal organs may be in place and starting to work together.
Tiny tooth buds have begun to develop, too.
Your baby’s fingers and toes are growing longer, and the webs that had been between each finger and toe are starting to disappear.
At the moment, your baby’s eyes, eyelids, and ears are continuing to develop, but they’ve still got some growing to do before they’re fully formed.
What’s in store for both you and your baby? Check out our Pregnancy Guide; it contains tips and insights to help you get through the rest of the first trimester and beyond. And even though it’s still too early to know your baby’s gender, you can have some fun with our Chinese gender predictor.
Related pregnancy tool
Fill in your info to get started:
Mom's age at conception
This is a mandatory field.
Baby's Due Date*//
Select date via the calendarPlease select a due date!
How Many Months Is 10 Weeks Pregnant?
Weeks or months? You’ll probably hear your pregnancy described in both ways, though weeks are more common. Though there are various methods of assigning the 40 weeks of pregnancy into months, at 10 weeks pregnant you’re likely in your third month of pregnancy, even if you haven’t noticed any belly bump or symptoms! “If I'm 10 weeks pregnant, when is my due date?” It's thrilling to think about the day you'll meet your new baby! Your healthcare provider will help you come up with this date, but in the meantime, try our Due Date Calculator to get an idea of when your little one may join the world.
How Big Is a Baby at 10 Weeks Pregnant?
Your little one is still growing very quickly! At 10 weeks, the average fetus is about the size of a strawberry, and your baby will likely measure approximately 1 inch long.
Your Baby: What Does 10 Weeks Pregnant Look Like?
Check out the illustration below for a look at how things are shaping up inside your belly as you head toward the end of the first trimester.
Your Body at 10 Weeks Pregnant
At 10 weeks pregnant, your uterus is about the size of a large orange, whereas before you became pregnant it was about the size of a small pear. Around this time, you likely have had or will soon have an appointment with your healthcare provider that includes an internal and external abdominal exam to determine the size and position of your baby.
Your healthcare provider might also perform blood tests to find out if you have any infections, determine your blood type and Rh factor, and check whether your own immunizations are up to date. There’s a lot to do, but your provider will be able to walk you through the details and schedule future appointments and tests.
10 Weeks Pregnant: Your Symptoms
“Why is week 10 of pregnancy the worst?” This may or may not be a question that's on your mind, but it’s not unusual for pregnancy symptoms to peak around this time, especially when it comes to nausea. The good news is that morning sickness and some other symptoms tend to lessen after the first trimester, giving way to a more comfortable and pleasant second trimester. At 10 weeks pregnant, here are some of the symptoms you may be experiencing:
Morning sickness. You’re not alone if you’re 10 weeks pregnant and still experiencing stomach pain, nausea, and other symptoms of morning sickness. Remember, there’s light at the end of the tunnel, but if you experience a more severe form of morning sickness called hyperemesis gravidarum, consult your healthcare provider.
Round ligament pain. This is one of the more uncomfortable pregnancy symptoms. Round ligaments are bands of tissue that support the uterus, and they stretch and soften as your baby grows during pregnancy. At 10 weeks pregnant, you might feel lower back pain or pain on your side when these ligaments tighten, such as when changing positions in sleep. Light stretching and gentle movements may help relieve the discomfort, but if it doesn’t go away on its own, or if you also have a fever, talk to your healthcare provider.
Minimal weight gain. Even though your clothes may be tighter, you may not have gained much weight—or you may have lost a little if you've been dealing with morning sickness. Read up on pregnancy weight gain and be sure to talk to your healthcare provider if you’re concerned. You can also try using our Pregnancy Weight Gain Calculator tool for an estimate of healthy weight gain based on your pre-pregnancy weight.
Exhaustion. You might feel like napping at every opportunity. This could be thanks to the increased levels of the hormone progesterone in your body. Sleeping while pregnant isn’t always easy, though, so be sure to consult your healthcare provider if you have any questions or concerns. Sleep is important!
Headaches. Pregnancy could trigger the occasional headache. If you're experiencing this symptom, try to rest in a darkened room and apply an ice pack to your head or neck to help relieve the pain. Contact your healthcare provider if the headache persists or is severe.
Mood swings. Hormonal changes may play a role in the highs and lows you feel when you’re about 10 weeks pregnant. You may find it helpful to distract yourself by chatting with friends, watching funny TV shows or movies, or treating yourself to a massage—just be sure to choose a trained massage therapist who knows about safe massage techniques for those who are pregnant.
Discharge. You might be seeing more vaginal discharge than before, which is caused by your increased blood supply and higher hormone levels. This normal discharge is clear to milky-colored, nearly odorless, and may appear slightly yellowish on your underwear. At ten weeks pregnant or later, contact your healthcare provider if you notice a strong odor or color changes in the discharge, or if you experience spotting, bleeding, or itching in the vaginal area.
Acne. If you’re experiencing acne now and didn’t before you got pregnant, or if your acne is worse now than before, it may be one of your pregnancy symptoms. Pregnancy acne is a hormone-related symptom and will likely clear up soon after your baby is born.
How Big Is a Pregnant Belly at 10 Weeks?
At 10 weeks pregnant, are you showing or just bloated, you may wonder? It’s possible that your pregnant belly’s size will increase at 10 weeks, but a baby bump doesn’t usually show until around weeks 12 to 16, even if you're pregnant with twins. This is when your uterus starts to move outside your pelvis area. Keep in mind that right now, your little one is only as big as a strawberry! Whether you're showing or not, you may be curious to know if you can feel your baby move at 10 weeks. Though your little one is probably moving around inside your uterus, they’re likely too small for any movements to be felt. Around 18 to 20 weeks you may experience what's known as quickening, meaning that you feel your baby move for the very first time.
What Does 10 Weeks Pregnant Look Like?
For a better idea of what your belly might look like around 10 weeks pregnant, when you’re in your third month of pregnancy, check out the image below.
10 Weeks Pregnant: Things to Consider
As you make your way through pregnancy, there are plenty of important things to consider, from adjusting your diet to caring for your body. Check out our list below.
Reduce your caffeine intake, if you haven’t already done so. Many healthcare providers recommend reducing or eliminating caffeine from your diet so that you’re not having more than 200 mg per day (the equivalent of one 12-ounce cup of coffee). Cutting out caffeine can also help you sleep better.
As your pregnancy progresses, the weight of your growing uterus can hinder blood flow to the lower parts of your body. When this happens, the veins in your legs can become swollen, sore, and blue. Varicose veins are not preventable, but you can take steps to ease the discomfort and prevent them from becoming worse.
Don’t sit with your legs crossed or stand or sit for long periods of time.
Try wearing support hose and propping your legs up whenever you can to help improve blood flow.
Also, stay active, move around, and add some safe pregnancy exercise to your daily routine if your healthcare provider approves.
As you anticipate your belly showing, 10 weeks is a good time to start taking pictures and starting a baby bump progression photo series, if this is something you might like to do. You could start as soon as you start showing, or even a little earlier. The series is easy to do:
Pick a day of the week, where you’d like to stand, and what to wear. Some wear a tight-fitting top, while others roll their top up to reveal their belly.
Stand to the side and either take a selfie or have someone take a full-length photo of you.
Once your baby is born, you can even take a few postpartum shots with your baby in your arms. You’ll love being able to look back on how your belly grew as your pregnancy progressed.
10 Weeks Pregnant: Questions for Your Healthcare Provider
Remember that your healthcare provider is always there for you, so feel free to consult them about any questions or concerns you have now and in the weeks to come. Some common questions at 10 weeks pregnant include:
When can I hear my baby’s heartbeat, if not at 10 weeks?
When will I be able to know if I’m pregnant with twins?
Are any genetic screening tests recommended? If so, when would these take place? Keep in mind that genetic testing is completely optional, and your healthcare provider can help you understand what risk factors or family history might impact your baby.
What is chorionic villus sampling and is it recommended?
Is a nuchal translucency ultrasound recommended?
10 Weeks Pregnant: Your Checklist
As you start to settle into your pregnancy and get used to the various emotional and physical symptoms, consider the following to-dos:
Get a professional bra fitting and buy comfortable underwear and well-fitting bras if needed.
Start to plan a second trimester babymoon! You’re nearly in the trimester that's sometimes called the “honeymoon” period of pregnancy, when you may get your energy levels back, so this could be the right time to take a short break. Besides, after the second trimester, you may not have the chance to get away for a while, so this might be the perfect time to book a relaxing trip.
When you have a minute, read up on pregnancy warning signs you should not ignore. You shouldn’t worry unduly, but it helps to be informed so you know what signs to look out for.
Child development by week | Regional Perinatal Center
Expectant mothers are always curious about how the fetus develops at a time when it is awaited with such impatience. Let's talk and look at the photos and pictures of how the fetus grows and develops week by week.
What does the puffer do for 9 whole months in mom's tummy? What does he feel, see and hear?
Let's start the story about the development of the fetus by weeks from the very beginning - from the moment of fertilization. A fetus up to 8 weeks old is called embryo , this occurs before the formation of all organ systems.
Embryo development: 1st week
The egg is fertilized and begins to actively split. The ovum travels to the uterus, getting rid of the membrane along the way.
On the 6th-8th days, implantation of eggs is carried out - implantation into the uterus. The egg settles on the surface of the uterine mucosa and, using the chorionic villi, attaches to the uterine mucosa.
Embryo development: 2-3 weeks
Picture of embryo development at 3 weeks.
The embryo is actively developing, starting to separate from the membranes. At this stage, the beginnings of the muscular, skeletal and nervous systems are formed. Therefore, this period of pregnancy is considered important.
Embryo development: 4–7 weeks
Fetal development by week in pictures: week 4
Fetal development by week photo: week 4
Photo of an embryo before the 6th week of pregnancy.
The heart, head, arms, legs and tail are formed in the embryo :) . Gill slit is defined. The length of the embryo at the fifth week reaches 6 mm.
Fetal development by week photo: week 5
At the 7th week, the rudiments of the eyes, stomach and chest are determined, and fingers appear on the handles. The baby already has a sense organ - the vestibular apparatus. The length of the embryo is up to 12 mm. nine0003
Fetal development: 8th week
Fetal development by week photo: week 7-8
The face of the fetus can be identified, the mouth, nose, and auricles can be distinguished. The head of the embryo is large and its length corresponds to the length of the body; the fetal body is formed. All significant, but not yet fully formed, elements of the baby's body already exist. The nervous system, muscles, skeleton continue to improve.
Fetal development in the photo already sensitive arms and legs: week 8
The fetus developed skin sensitivity in the mouth (preparation for the sucking reflex), and later in the face and palms.
At this stage of pregnancy, the genitals are already visible. Gill slits die. The fruit reaches 20 mm in length.
Fetal development: 9–10 weeks
Fetal development by week photo: week 9
Fingers and toes already with nails. The fetus begins to move in the pregnant woman's stomach, but the mother does not feel it yet. With a special stethoscope, you can hear the baby's heartbeat. Muscles continue to develop. nine0003
Weekly development of the fetus photo: week 10
The entire surface of the fetal body is sensitive and the baby develops tactile sensations with pleasure, touching his own body, the walls of the fetal bladder and the umbilical cord. It is very curious to observe this on ultrasound. By the way, the baby first moves away from the ultrasound sensor (of course, because it is cold and unusual!), And then puts his hands and heels trying to touch the sensor.
It's amazing when a mother puts her hand to her stomach, the baby tries to master the world and tries to touch with his pen "from the back". nine0115
The development of the fetus: 11–14 weeks
Development of the fetus in the photo of the legs: weeks 11The baby, legs and eyelids are formed, and the genitals become distinguishable (you can find out the gender (you can find out the gender child). The fetus begins to swallow, and if something is not to its taste, for example, if something bitter got into the amniotic fluid (mother ate something), then the baby will begin to frown and stick out his tongue, making less swallowing movements. nine0003
Fruit skin appears translucent.
Fruit development: Week 12
Photo of the fetus 12 weeks per 3D Uzi
Development of the fetus for weeks: Week 14 9000 9000buds are responsible for production for production urine. Blood forms inside the bones. And hairs begin to grow on the head. Moves more coordinated.
Fetal development: 15-18 weeks
Fetal development by weeks photo: week 15The skin turns pink, the ears and other parts of the body, including the face, are already visible. Imagine, a child can already open his mouth and blink, as well as make grasping movements. The fetus begins to actively push in the mother's tummy. The sex of the fetus can be determined by ultrasound.
Fetal development: 19-23 weeks
Fetal development by week photo: week 19Baby sucks his thumb, becomes more energetic. Pseudo-feces are formed in the intestines of the fetus - meconium , kidneys begin to work. During this period, the brain develops very actively.
Fetal development by weeks photo: week 20The auditory ossicles become stiff and now they are able to conduct sounds, the baby hears his mother - heartbeat, breathing, voice. The fetus intensively gains weight, fat deposits are formed. The weight of the fetus reaches 650 g, and the length is 300 mm.
The lungs at this stage of fetal development are so developed that the baby can survive in the artificial conditions of the intensive care unit. nine0003
Fetal development: 24-27 weeks
Lungs continue to develop. Now the baby is already falling asleep and waking up. Downy hairs appear on the skin, the skin becomes wrinkled and covered with grease. The cartilage of the ears and nose is still soft.
Fetal development by week photo: week 27Lips and mouth become more sensitive. The eyes develop, open slightly and can perceive light and squint from direct sunlight. In girls, the labia majora do not yet cover the small ones, and in boys, the testicles have not yet descended into the scrotum. Fetal weight reaches 900–1200 g, and the length is 350 mm.
9 out of 10 children born at this term survive.
Fetal development: 28-32 weeks
The lungs are now adapted to breathe normal air. Breathing is rhythmic and body temperature is controlled by the CNS. The baby can cry and responds to external sounds.
Child opens eyes while awake and closes during sleep.
The skin becomes thicker, smoother and pinkish. Starting from this period, the fetus will actively gain weight and grow rapidly. Almost all babies born prematurely at this time are viable. The weight of the fetus reaches 2500 g, and the length is 450 mm. nine0003
Fetal development: 33-37 weeks
Fetal development by week photo: week 36The fetus reacts to a light source. Muscle tone increases and the baby can turn and raise his head. On which, the hairs become silky. The child develops a grasping reflex. The lungs are fully developed.
Fetal development: 38-42 weeks
The fetus is quite developed, prepared for birth and considered mature. The baby has mastered over 70 different reflex movements. Due to the subcutaneous fatty tissue, the baby's skin is pale pink. The head is covered with hairs up to 3 cm.
Fetal development by weeks photo: week 40The baby perfectly mastered the movements of his mother , knows when she is calm, excited, upset and reacts to this with her movements. During the intrauterine period, the fetus gets used to moving in space, which is why babies love it so much when they are carried in their arms or rolled in a stroller. For a baby, this is a completely natural state, so he will calm down and fall asleep when he is rocked.
The nails protrude beyond the tips of the fingers, the cartilages of the ears and nose are elastic. In boys, the testicles have descended into the scrotum, and in girls, the large labia cover the small ones. The weight of the fetus reaches 3200-3600 g, and the length is 480-520 mm. nine0003
After the birth, the baby longs for touching his body, because at first he cannot feel himself - the arms and legs do not obey the child as confidently as it was in the amniotic fluid. Therefore, so that your baby does not feel lonely, it is advisable to carry him in your arms, press him to you while stroking his body.
And one more thing, the baby remembers the rhythm and sound of your heart very well . Therefore, you can comfort the baby in this way - take him in your arms, put him on the left side and your miracle will calm down, stop crying and fall asleep. And for you, finally, the time of bliss will come :) . nine0003
Left, right. Scientists have found that a person has not only a "leading" hand, but also a leg, an ear and an eye
Read also
How the Mayan script was deciphered and why the first IT people were engaged in telepathy: 4 excellent books of non-fiction The Frankenstein mystery: how a writer who ran away from home with a strange husband spoke through the mouth of a monster Status is more valuable than money: why the position in society is critical for healthPexels
Why alone one third of the world drives on the left and two thirds on the right? Why does European writing go from left to right, while Arabic and Hebrew go from right to left? Science has already found answers to some questions, but it still struggles with some paradoxes of asymmetry in nature, body and culture. The book "Why the heart is on the left, and the hands of the clock move to the right. Secrets of the Asymmetry of the World” by Professor Chris McManus, which received the Royal Society of London Prize for the Development of Knowledge of Nature for the Popular Science Book of the Year, was recently published in Russian. nine0008
Bombora
With the permission of the Bombora publishing house Vedomosti. City" publishes an excerpt.
In general, both in the UK and throughout the West, left-handed people make up just over ten percent, although the proportion is slightly lower among older people and in some other regions of the world.
If among men there are 11.6% left-handers, then among women - only 8.6%. That is, for some reason, left-handedness is more characteristic of men than women. This result has been replicated many times in many studies, and overall found that there are just over five left-handed men for every four left-handed women. Not a very big difference, but it seems to persist forever and should reflect something important in the biology of left-handedness. Signs of this gender difference can be seen even in the family of Charles Darwin himself, in which three out of eight men (38%) and only one in six women (17%) were left-handed. nine0003
Right-handedness is more pronounced than left-handedness. This is partly due to the fact that left-handers live in a “right-handed world”, where a variety of objects, from a microwave oven to a computer or piano keyboard, are arranged mainly “under the right hand”. As a result, left-handers are forced to adapt to a right-handed world and often use their right hand despite their natural inclination to use their left.
"Left-footed" soccer players and dominant eyes
Although right-handed versus left-handed people have been discussed so far, some prefer to talk about favoring one side or the other, because many behaviors seem to be associated with a preference for one side of the body and involve hands, feet, eyes, ears, etc. Some of these asymmetrical acts correlate with left- and right-handedness, but not all. The tendency to use one or the other hand fully applies to the legs: as a rule, for right-handers, the leading foot is the right, for left-handers, the left. It's easy to check this - ask someone to kick the ball into the goal, and the foot that kicks the ball will be the leading one. nine0003
This property of professional football players is assessed by which foot they dribble the ball more often - left or right. Most of them use their lead foot 85% of the time, and almost no one uses both feet equally often. In other words, even professional football players do not use both legs equally well, they are not ambidexters in this sense. Like all other people, twenty percent of footballers are "left-footed", and this proportion is significantly higher than the usual ten percent left-handed for any population. nine0003
You can also determine the dominant ear - mainly by which of them people hold the phone. About 60% prefer to listen with the right ear, 40% - with the left, right-handers prefer the right, left-handers prefer the left. Although this feature has been little studied in the past, the situation is now changing with the near ubiquity of mobile phones.
In contrast to the almost imperceptible "leading ear" problem, the question of the dominant eye has been studied more thoroughly. To determine which eye is your dominant eye, stretch out your hand and point to a small object in the distance. Now close one eye. If the finger is still aligned with the object, then the open eye will be the leading one. If you look with the other eye, not the leading one, then the finger will no longer point at the object. This is "sighting", or ocular, dominance - the preference to see the object with one or the other eye. The dominant eye is easily determined if you ask which eye a person looks through the keyhole or into the eyepiece of a microscope. About 70% of people prefer to look with the right eye, about 30% - with the left. Although lefties tend to favor the left eye and righties tend to favor the right, many people are crosslateral, meaning their dominant eye and dominant hand do not match. nine0003
Exercises for the Curious
There are many other functional asymmetries that usually do not attract much interest - for example, most people prefer to chew with the right side of their jaws. And yet I have long been interested in two features, completely trivial and unimportant - how people fold their arms and cross their hands. To test this, quickly bring your hands together so that your fingers are intertwined. Which thumb is on top, right or left? Now try to do it the other way around, and you will have to think for a moment, the action itself will take longer, and it will even seem that the fingers are intertwined not so conveniently. The first instinctive movement you made was easier and more natural. This movement is not learned, in fact, people don't even notice it unless they are pointed out to it. nine0003
In Britain, almost 60% of people have the left thumb on top, and this proportion is the same for right-handers and left-handers. It is particularly interesting that as one moves east—through Europe, Asia, and toward Oceania—the proportion of those with the left thumb on top decreases, and in the Solomon Islands, east of New Guinea, only thirty percent of people have the left thumb on top. . Even more puzzlingly, this property is transmitted in the genus, although rather weakly, so that the child of parents who have the left thumb on top is most likely to inherit this feature. nine0003
Another asymmetry that you can test for yourself is the folded hands. Cross your arms quickly. Which wrist is on top, right or left? Now try it differently. When I asked to do this in a lecture, there was invariably a burst of laughter, when people, twirling their hands in front of them, invariably realized that they had come to the same place where they started - the same wrist was on top all the time. Trying to place the other wrist on top was invariably difficult, you had to think about it, and it felt strange. In the UK, the left wrist is on top in about 60% of people, and this proportion is the same not only among right-handers and left-handers, but also among those who, when crossing their hands, the right or left thumb is on top. Thus, left-handedness and right-handedness, crossing of the hands and folding of the hands have different causes. The list of small asymmetries is almost endless. For example, one in five people can move their ears, and of those who can only move one ear, there are twice as many who can only move their left as those who can only move their right. Surprisingly and strangely enough, but the reasons for the existence of this kind of asymmetry are currently almost completely unknown. nine0003
However, the preference for left or right does require an explanation, and for many reasons, scientists have put a lot of effort into behavioral asymmetries.
Is the child right-handed or left-handed?
So when does it become clear whether a child becomes right-handed or left-handed? Determining the dominant hand in young children is not easy, especially in the first two years of life. In particular, it seems that there is a certain stage known as the "chaotic phase", when the child almost daily prefers one or the other hand - today the right, tomorrow the left. nine0003
Since the dominant hand can be clearly identified only in the second year of life, scientists did not see much point in studying which side the child prefers before this age. However, fetal behaviorist Peter Hepper of Queen's University Belfast vehemently dismisses this approach as misguided. With the help of ultrasound scanning, he studied several hundred unborn babies and found out that the fetus sucks a finger in the womb after 12 weeks of pregnancy, and at more than 90% of cases it is the finger of the right hand. There is a temptation to explain this by brain asymmetry, since the first signs of asymmetry of the cerebral cortex are also found at the same stage of development. However, later Hepper, studying the behavior of a ten-week-old fetus, found out that at this stage the finger is not yet sucked, but the arms and legs are already moving. He decided to find out which hand the fetus moves more often - and it turned out that in 85% of cases - the right one. This cannot be taken as an indication that the asymmetry of the brain occurs earlier than previously thought, because at such an early stage of development, the neurons of the brain are not yet connected to the spinal cord. Such an early asymmetry of behavior is thus associated with the spinal cord or with the limbs themselves, and therefore there is a possibility that the preference for one side or another is formed not in the cerebral cortex, but at some lower level of the nervous system, but as well as on which one is still unknown. nine0003
It is indisputable, however, that left-handedness and right-handedness are a family trait. Some time ago, the late Phil Bryden and I went through every paper on this subject that we could find in the scientific literature, which together amounted to more than 70,000 children whose parents were either only right-handed, only left-handed, or, as in the family Darwin, one of the parents was right-handed, the other was left-handed.