Pregnancy is a marvelous thing. You’re growing an actual human being in there. Well done! It may also be daunting, you might feel a bit rubbish and sometimes it’s hard to picture what’s going on inside. This week to week guide gives you an idea of what baby is doing and how they are developing.
Pregnancy Week One to Three
Strictly speaking, many people don’t start counting pregnancy as week one to three as this is where they are counting down from the end of one period to another. When a doctor or midwife asks when your period was, they use this information to date the pregnancy.
Pregnancy Week Four
This is when the magic really starts to happen. From week four and across week five the embryo starts to develop and grow. This takes place within the womb lining. At this stage the embryo grows and develops within the lining of the womb and cells start to link up with your (the mother’s) blood supply. At this point the embryo is attached via a super-small sac from which they gain their nourishment.
Pregnancy Week Five
Week five occurs right at the point of your first missed period. It’s at this point that women might first start to suspect that they may be pregnant. Already the baby’s nervous system is starting to develop, getting things ready for the major organs to start to grow. At this point they are only a tiny 2mm long.
Pregnancy Week Six
Right now the embryo starts to look like a little tadpole. Other nicknames include shrimp and prawn. Your tadpole is covered in a thin see-through skin of sorts and if you could see it you’d find a bump at one end, the head and another at the other end. One of these will become the head and brain, and the other is the heart. During an early scan (vaginal scan) the heart may be able to be detected at this point). Little “buds” will soon be present if they aren’t already. These are the start of ears and limbs such as arms and legs.
Pregnancy Week Seven
By week seven the embryo has had something of a growth spurt and is now measuring approximately 10mm from the bottom to the head. This is often referred to as the crown-rump length. The head is growing quickly, as is the brain so the embryo may look a little out of proportion at this stage! The inner ear is starting to develop now, and the eyes will continue to grow. At this point the spinal cord, or nervous system as well as the brain are developing well.
Pregnancy Week Eight
Your embryo is no longer an embryo. It is now a foetus. Your feotus is growing and developing rapidly now. The legs are starting to get longer, although the different parts of the leg, i.e the thighs and knees haven’t yet developed. The feotus is still gaining nourishment from the yolk sac and is still within the amniotic sac. The placenta is developing and will soon start to attach properly to the wall of the womb.
Pregnancy Week Nine
The feotus’ face is now starting to form so that it is becoming more like you would expect a face to look. Eyes are now starting to look like eyes and will even have some colour in them. The mouth is also present, as is the still-forming tongue which already has some tiny taste buds.
Major organs are quickly developing now, for example, the heart, lungs, brain, kidneys and so on. You might see feet and hands starting to develop although you wouldn’t be able to see fingers and toes as the feotus hasn’t quite reached this stage. Not far off though!
At week seven you had a 10mm embryo, at week nine you have a strapping big 22mm feotus.
Pregnancy Week Ten
The face is developing well now, with ears starting to emerge and defined ear canals growing inside. Nostrils are visible, as is the upper lip. Believe it or not, at ten weeks not only are the jawbones developing fast, they already contain all the milk, or “baby” teeth!
The heart is now a fully formed and functioning organ. The heart will beat faster than yours, up to three times faster.
If you had an ultrasound scan during week ten you would be able to see the baby making small movements.
Pregnancy Week Eleven
The baby’s face is now formed, although the ears will continue to grow to look more like ears. The eyelids remain closed for a good couple of months yet. The head is still significantly larger than the rest of the body but the rest is catching up fast. At this stage, the baby’s fingers and toes are starting to separate into recognisable hands and feet, including having fingernails etc in place.
Pregnancy Week Twelve
The baby becomes fully formed around week twelve. This means that the baby’s job is to continue to grow but that the major organs, muscles, limbs and even the sex organs are all fully developed or very close to being. The baby is moving around a little more now although it’s unlikely that you’d be able to feel it at this stage as the baby is still very small.
The cartilage-based skeleton of the baby is now developing into a harder bone.
Pregnancy Week Thirteen
The baby continues to mature and grow. During week thirteen sex organs, testis or ovaries will be fully developed inside the body and genitals are developing outside. You would be unlikely to be able to see the gender of a baby at this point though.
Pregnancy Week Fourteen
The baby is now approximately eighty five millimetres long (crown to rump measurement). It’s at this stage that the baby’s kidneys start to work as they begin to swallow a little of the amniotic fluid around them, which in turn moves through the stomach and is expelled as urine. The first wee (it’s amazing what parents can get excited over in terms of milestones both before and after baby is born)!
From Week Fifteen
During week fifteen your baby may be able to start to hear muffled sounds, both from the outside world and from you. They will be able to hear the rumblings of your digestive system as well as the sound of your heart and when you speak.
The baby’s eyes are still closed however they may start at this point to be able to see and recognise brighter lights from outside of the womb/ your body.
From Week Sixteen
The baby’s hands are not only fully formed, they may now form a fists and reaction to each other, i.e. grasping hold of each other when they touch.
Facial expressions are starting to develop as the muscles in the face are now able to properly move however the baby doesn’t have any control over these so they are random.
From Week Seventeen Through to Week Twenty
After week seventeen the baby is looking more like a baby, being fully developed and having facial features, including hair such as eyebrows and eyelashes. The eyes are moving behind closed eyelids and the mouth will be opening and closing.
The baby has developed a firm grip and not only are toenails and fingernails still growing, baby now has a full set of fingerprints! Baby is able to hear and react to more noise and will be moving around and even responding to these noises. Although baby is now weighing around 150g these movements may be hard to detect, particularly if it is your first pregnancy. You might be able to feel the odd fluttering though between seventeen and twenty weeks.
Baby has put weight on but still has a lot of growing to do, particularly when it comes to gaining fat. By the end of twenty weeks the baby will be covered in vernix which is a white, grease-like covering that protects the baby’s skin during the remaining weeks spent in the womb and surrounded by amniotic fluid.
Week Twenty-One Through to Week Twenty Four
By the time baby is twenty one weeks old they will weight approximately 350g which is more than the placenta weighs. The placenta is still growing but baby will always be bigger than it now. During this period baby becomes covered in fine hair which known as languo. There is still debate over what the purpose of languo is however many believe it is to keep your developing baby warm as it’s usually gone just before baby is born.
While the baby gets all the oxygen they need from you via the placenta because while they are present the lungs aren’t mature enough to be working, baby will be stimulating breathing movements. These will become practiced movements by the time they are born and their lungs are properly working.
Already the baby is starting to find their own sleeping pattern. Sadly this pattern may not necessarily be the same as yours! This means that baby might sleep as you move and be wide awake and moving while you’re asleep.
Thanks to the advancements in neonatal care it is by the end of week twenty four that a baby might be able to survive outside the womb. They would need a lot of extra care and would be very frail and are not guaranteed at this stage to survive and be well as they aren’t quite developed enough. The fact that it is possible in the right circumstances just goes to show though much baby has developed by the twenty four week point.
Week Twenty-Five Through to Week Twenty Eight
At this stage your baby’s heartbeat will have slowed down a little but will still be faster than yours. Baby responds well to both sound and touch, and will even “jump” or move around more to loud/sudden noises or to touch. It is during this stage that baby’s eyelids are starting to open up for the very first time and before long baby will also be able to blink. Your baby is still taking swallows of amniotic fluid and passing urine but now may get hiccups. Many women say that when they feel this it can feel like a slight popping feeling or similar.
Your baby is fully developed but still needs to grow and mature as well as put on more weight/fat. By the end of 28 weeks the baby’s heartbeat is strong and will weigh approximately one kilogram.
Week Twenty Nine Through to Thirty Two
Now that baby has developed fully his or her job is to continue to grow, and for their body to mature, ready for life on the outside. You’ll be able to feel baby much easier now, and should start to notice a pattern of movements that occur daily. If these movement patterns change let your midwife or maternity unit at the hospital know.
Not only is baby filling out nicely, he or she is starting to suck their fingers or thumbs.
Baby might be lying head down by now which is called the cephalic presentation however if not don’t worry, there’s still time.
Weeks Thirty Three Through to Thirty Six Weeks
Baby now has harder bones, apart from the skull which remains soft until after baby is born (making being born and still keeping the brain secure possible). The brain will be fully developed, as is the nervous system which has been developing steadily from the very early weeks of pregnancy.
Baby is getting a little cramped in your uterus now but is still able to move about so you’ll be able to feel, and even see movements. By the end of thirty six weeks your baby’s lungs should be well-equipped for breathing on their own after they are born. The baby will also have a digestive system and a suckle reflex ready for feeds.
Week Thirty Seven Through to Forty Weeks
Full-term in pregnancy is reached by thirty seven weeks which means that your baby is ready and fully equipped for living outside of the womb. Baby’s gut now contains meconium which is the first (somewhat yucky and green) poo the baby has after birth. Baby will be losing or have lost the languo it was previously covered with (the fine hair that covered baby’s body).
Between thirty seven and forty weeks baby will move head down if they haven’t already, ready for birth.
Forty Weeks Onwards
By now baby might have arrived. If not you may be looking at induction. How far you may go before induction will depend on the area that you live in and the hospital trust providing your care. Baby should be fully developed, the lanugo covering the baby will most likely have gone, or nearly all gone, and baby will be ready to meet you!