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Life Before Birth

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The miracle of life that starts with just a single egg and a single sperm may be even more incredible than we think...

by Stuart Carter

New ultrasound techniques - 3D and 4D scans are opening up a unique portal on the miracle of life that starts with just a single egg and a single sperm. With remarkable findings revealing that the foetus dreams, jumps, sucks it thumb, open it eyes and reacts to pain far earlier that ever realised before. The essential senses, hearing and seeing also develop far earlier that we had ever realised.

It all starts with a humble sperm – and there are loads of them – around 300 million per ejaculation to be exact – and the largest cell in the body - the female egg. In 9 months (38 weeks) this single fused cell will grow to 2 trillion cells with 200 different cell types – a complex self sustaining human baby.

A sperm can survive for about 48 hours (yes 48 hours!) and it can take 10 hours to reach its destination – the female cell waiting in the fallopian tube - swimming at the mightily impressive rate of 3mm per hour. Natural selection is as brutal here as anywhere in the outside world – only a few healthy sperm will make the entire journey and the first to penetrate the female cell wall will be the winner. Within 12 hours the nuclei of sperm and egg fuse and the blueprint for building a new human is complete. The 23rd chromosome determines the sex of the baby – all the mothers eggs have X chromosomes and the sperm carry either X or Y in equal proportions. If the X sperm gets through then it’s a girl and if it is the Y a boy.

Life Before Birth

Pregnancy is divided into 3 equal blocks called 'trimesters'. In the first trimester, up to 9 weeks, the foetus will form a complete human body with limbs, nerves, organs and muscles. This is the most fragile part of the pregnancy when the foetus is most at risk. After around 2 months the whole body begins to move and twitch. The placenta has formed and has taken over from the yolk sac the job of providing nourishment for the embryo. The intestines are formed and the foetus can move its legs and head but the eyes remain fused shut. Even at this early stage the foetus responds to stimulation – when prodded its tiny hands will close – and this is the point at which its own heart beat can be heard with a stethoscope. In fact 4D scans reveal that the foetus can already suck, yawn and swallow - possibly all automatic reactions. Is the foetus practicing for when it will burst in to the real world? At about 9 weeks the foetus starts announcing its existence with a series of leaps, using the walls of the uterus like a trampoline. This early on there is still plenty of space in which to flex its muscles. By the end of the first trimester everything is in place – ready to develop and grow.

Throughout the 2nd trimester the limbs start to function more fully. Now there is much less risk of miscarriage. The fist normal ultrasound scan takes place around 11-14 weeks to establish an accurate delivery date and to measure the crown to rump length and make sure everything is okay. The scan could reveal Downs Syndrome or other genetic abnormalities. It might also reveal twins. In fact twins are fascinating because their close bonding starts in the womb where there is close contact of arms, legs and mouths. Non identical twins are separated by a membrane as there are two separate placentas. Multiple births run in families – if your mother had twins then you are more likely to have them too. At the fist scan this is always a shock, but also a delight to the families – especially when they can hear two distinct heart beats. At 10 weeks the genitals can be clearly seen, but it is still hard to be sure if it is a boy or a girl. In a girl the tiny ovaries are already producing her lifetime supply of eggs and in a boy the rudimentary testicles are already producing testosterone.

4D Ultrasound 28 Weeks

At around 4 months the foetus can be seen playing with its own umbilical cord – often getting it wrapped around its body. But it is still very elastic and presents no danger at this stage. When prodded through the abdomen the baby squirms – it can bend and twist its fingers, hands, wrists and toes. The heart has settled to around twice an adults heartbeat rate – 120-160 bpm.

One of the most important reactions the baby will have is now developing – the grasping reaction. It will spend plenty of time practicing by holding on to the umbilical cord, the other hand, toes, feet and face. In the case of twins they hold on to each other. Digestive and urinary tracts are in full swing with the baby swallowing and circulating its own amniotic fluid – breathing the fluid in and out of its liquid filled lungs all the time. This is around the time the baby’s mother will feel its movements for the first time.

The eyes were previously thought to remain fused until around 24 weeks. But 4D ultrasound scans have revealed babies opening their eyes by the 16th week. It’s dark in there but the eyes are still not fully functional anyway. By the 18th week the foetus has reached the half way stage. At 21 weeks, the end of the second trimester, everything is fully formed if not fully grown. At this stage a few babies can survive outside the womb but most would still die or suffer from severe difficulties. But most will remain where they are and put on a bit of weight and practice some vital skills for survival in the outside world.

The mother is becoming increasingly aware of the changes happening inside her body. Her baby can taste and smell the amniotic fluid in which it lives. Doctors know that the amniotic fluid can taste of garlic, onion and even curry. Too much spice and the foetus will stick out its tongue! And it can hear not only what goes on inside the womb, but also the rest of its mother’s body and sounds from the outside world. The most dominant sound is the mother’s heartbeat, followed by the gurgling in her stomach. Strangely it can hear it father’s voice best if he is close – the lower frequency waves can penetrate the abdomen wall more easily.

Credit - David Barlow

It is thought that the foetus can sense pain from 24 weeks on – and possibly even earlier. This is also the time the baby could be born and stand a chance of surviving – and it is also the latest time that abortions can be carried out in the UK or the USA. The baby can now open its eyes regularly – but only the very brightest light can get through the abdomen wall. At 25 weeks the eyes are fully formed but the pigment will only mature when it is born – the pigment cannot properly form without light. The baby will drink 2 litres a day of amniotic fluid. It serves no nutritional value but does help perfect the art of swallowing – so important for later survival.

Foetuses spends around 90% of their time asleep but when they are awake they can be full of beans, often exhibiting the ‘startle’ reflex where it throws it arms and legs out if it hears a loud noise. The baby has been hard at work sucking its thumb since the 11th week. By the 25th week it will suck its fingers, toes - in fact anything it can get hold of. At week 26 it is possible to hear the foetuses own heartbeat by pressing your ear to the mother’s abdomen. Its heartbeat is twice as fast as it mother’s. And it ‘breathes’ just like a newborn, except that its lungs are filling with fluid rather than air. The air sacs inside the lungs are still closed and will not open until the moment of birth.

By the 7th month the baby kicks and hiccups just like a new born. And when it is asleep 4D scans reveal that it experiences REM – rapid eye movement - as far as we are aware a clear indication of dreaming. What is it dreaming of – its mother’s voice, her heart beat or the loud noises outside? We don't know.

The cry of a new born baby already exhibits some of the speech features and rhythms of its parents. A French newborn baby prefers to look at a French speaking person and a Russian newborn at a Russian speaker. Incredible but true. And fast music can stimulate the foetus. Music similar to the heartbeat rhythm will have a soothing effect but faster music will agitate it. At 32 weeks a foetus can recognise a piece of music and move in time to it. Also it can remember things extremely well. If its mother has watched a lot of one soap opera – after it is born it is more likely to be calm and quiet when that programme is playing on the TV. So our bad TV habits start before we are even born!

Credit - David Barlow

By the 9th month the baby inverts itself so the head is pointing down ready for its exit into the big wide world. The baby is putting on weight – mostly fat – with less and less space to move around inside it mother. How the birth process starts is still a mystery but we know it has something to do with the placenta. At some point the placenta stops the release of progesterone and this somehow kicks off contractions in the uterus wall. During the first phase of labour the cervix expands to allow the baby to pass through. Birth is a particular problem for humans – our brains and therefore our heads are large and this is the trickiest part to get out of our mothers. Large amounts of adrenalin are released inside the baby to keep its heart going just in case the umbilical cord is squashed and the oxygen supply is cut off. The adrenalin also helps kick start the lungs for a lifetime of work.

Finally after 9 months the baby is thrust into a bright, noisy world. For the fist time the baby has to breathe and feed on its own. As its incredible odyssey inside the womb comes to an end another journey begins – the journey of life.



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First Science 2014