Your pregnancy week by week

Conception

Your baby When the head of the sperm meets the nucleus of the egg, fertilisation occurs – the egg and sperm fuse to create one cell, the zygote, which divides again and again to form the placenta and the embryo. 

These cells take around four days to reach the uterus and by day seven, the cell cluster – now known as a blastocyst – has implanted in the uterus wall.

Your body Seven days after implantation, chemical signals are sent to stop your period. Around 12 days after fertilisation, a pregnancy test will be able to detect the presence of the hormone human chorionic gonadotrophin (hCG), which is produced by the placenta.

0-5 weeks pregnant

Your baby Your baby’s heart, which is about the size of a poppy seed, beats at about 150bpm (beats per minute). Her neural tube will fuse this week (which is why taking folic acid before conception and during the first three months is recommended to reduce the risk of neural tube defects like spina bifida).

Your body The first hormone-induced signs of your pregnancy may start to appear now. Your boobs may feel tender and your sense of smell may become more acute.

6-8 weeks pregnant

Your baby Still an embryo, your baby has eye, ear and limb buds and her nervous system is developing. She’ll be growing rapidly now, reaching around 4mm by the end of week six. By week seven, she’ll measure around 9mm from crown to rump – the size of a small bean. By week eight, she’ll have developed the startle reflex (see box).

Your body Morning (noon and night) sickness might affect you now and hormones will be slowing down your digestive system, so you can add indigestion and bloating to the menu of early pregnancy symptoms. By week eight, your uterus will be about the size of an orange.

9-10 weeks pregnant

Your baby Her internal sex organs have developed and her liver has started producing red blood cells. Her body is catching up with her head in terms of growth and she’ll lose her comma-like shape as her tail disappears. She’ll weigh around 0.3 of an ounce.

Your body Your boobs will have grown noticeably and the area around your nipples – the areola – may begin to darken. You might also find that the veins in your boobs become more pronounced.

By week 12 pregnant

Your baby All her body parts are present and she’s now officially a fetus. Her intestines have moved from the umbilical cord back into her abdomen and her lungs will be filling up with amniotic fluid and emptying as she practices breathing. She’ll have the beginnings of fingernails and fine, downy hair all over her body.

Your body A dark line of pigmentation – the linea nigra – may appear on your abdomen and your growing uterus, now about the size of a grapefruit, will push itself above your pelvic bone.

You’ll start to feel hotter than usual because of all the extra blood circulating around your body.

Your unborn baby’s first reflex is the startle reflex, also known as the Moro reflex. By two months in utero, your baby will hear sound and react to it by opening and closing her arms and legs.

At birth, the Moro reflex will cause your baby to throw her arms and legs wide, extend her hands and fingers and open her eyes wide if she is disturbed by a sudden bright light, loud noise or touch, or if she feels she is about to be dropped.

This reflex will become less pronounced about three months after she’s born and should disappear completely by the time she’s eight months old. The Moro reflex is believed to be a hang over from our primate days, when babies clung to their mothers’ bodies for security.

Second trimester

The next three months will see your baby growing rapidly and discovering her environment  

Weeks 13-16 pregnant

Your baby With much of her organ development complete, your baby will spend the rest of her time in the womb growing in size and strength. This month of your pregnancy will see her grow more than at any other time in your pregnancy and she’ll be very active in the womb.

Her nervous system will be up and running and she can suck her thumb and swallow and react to the sounds echoing through your amniotic fluid. By 16 weeks she’s around 14cm long and weighs around seven ounces. 

Your body Now you’ve entered your second trimester, symptoms like morning sickness and exhaustion should abate, leaving you feeling buoyed up on hormones and feeling fantastic, that’s the theory anyway.

Hormones can change the condition of your hair and skin and whether you end up with greasy locks and spots or shiny hair and a glowing complexion is very much down to the luck of the draw.

Weeks 17-20 pregnant

Your baby Her entire body is coated with hair – called languno – which helps to keep her warm until her body has laid down enough fat. She’ll also be covered in vernix – a waxy substance that protects her delicate skin from the amniotic fluid.

Her limbs have reached their relative proportions and fat is starting to be deposited at the nape of her neck, behind the breastbone and around the groin and kidneys. She’ll have her own unique fingerprints now.

Your body Your uterus will start to move up above your navel, making your pregnancy visible. Some women get spots of pigmentation on their face – known as chloasma or the ‘mask of pregnancy’ – these will disappear within 12 weeks after the birth. You may feel your baby’s movements for the first time (see box).

Weeks 21-24 pregnant

Your baby Her bones are beginning to harden and her skin is sensitive to touch (apart from her scalp which is desensitised for labour and birth). She’ll appear red and wrinkly and her bones and blood vessels are visible as she doesn’t have subcutaneous fat under her skin.

Her eyes are still closed although by 21 weeks rapid eye movement – associated with dreaming – will begin. She’ll grasp and play with the ubliical cord, and you’ll be able to feel when she gets hiccups!

Your body Hormones continue to soften your muscles and ligaments to help your body bear your extra weight (healthy weight gain is 1lb or 16oz a week during the second trimester).

Weeks 25-28 pregnant

Your baby

Your baby will grow by half her body length and triple in weight, her eyes will open and her eyelashes will grow. The connection between the part of her brain responsible for pain and emotional perception and the cerebal cortex, or thinking part of the brain, will become more established and she’ll start to remember and learn from hearing and feeling your movements as well as her own. By 28 weeks she’ll be around 26.5cm long and weigh about 1.3kg.

Your body

You’ll feel aches and pains thanks to your increased weight and your increased blood supply can lead to varicose veins and piles. From around 27 weeks you may experience Braxton Hicks contractions which prepare your body for labour. You’ll feel a tightening or hardening of your uterus, which will last from 30 seconds to two minutes.

Between 18 and 20 weeks, you’ll start to feel your baby moving around in your womb. If this is your first baby you might feel these movements later than in subsequent pregnancies. Although your baby has been active for some time, it’s only from around 18 weeks that her movements are strong enough for you to feel.

Many women describe a fluttering sensation – known as ‘quickening’ – in their lower abdomen.

Third trimester

Her lungs are working and she’s laying down fat in preparation for being born 

Weeks 29-32 pregnant

Your baby You’ll notice that your baby’s movements take on a pattern as she starts to have periods of sleep and wakefulness. She’ll open and close her eyes often and will kick vigorously, although her movements will decrease as she has less space in your uterus.

She’ll recognise your voice and any music that she’s exposed to regularly. As more fat is laid down, her skin loses its red, wrinkly appearance.

Your body As your body gears up for the birth, your breasts may leak colostrum (pre-milk) and you may find things like getting in and out of the bath become quite difficult thanks to your expanding bump and pressure on your lower back and pelvis.
It’s common to have some swelling in your lower legs and ankles but if your hands or face swell, contact your doctor or midwife immediately as this could be a sign of pre-eclampsia.

Weeks 33-35 pregnant

Your baby Her fingernails will be fully grown now and her lungs are secreting a surfactant that will keep them expanded after birth and allow her to breathe. Her eyes are blue and her head grows more than the rest of her body to accommodate her expanding brain. She’ll pass nearly a pint of wee a day into the amniotic fluid.

Your baby will measure approximately 31cm crown to rump by the end of week 35 and weigh around 5lb – she’ll continue to put on about 8oz a week until she’s born.
Your body You may become quite breathless as your baby compresses your lungs.

Your uterus can throw your posture off, giving you that pregnant ‘waddle’ and you may find it difficult to find a comfortable position to sleep in. Pain in your pelvis could indicate that you’re putting the muscle under too much strain as it softens.

Weeks 37-40 pregnant

Your baby If this is your first pregnancy, your baby’s head might engage in week 36, which means she moves down into your pelvis in preparation for being born. In subsequent pregnancies, your baby’s head might not engage until labour begins.

Her lungs are mature enough to breathe air and her hearing is good, although her eyesight will continue to develop outside the womb (at birth, she’ll be able to focus on your face when she’s held at your breast).

In the final weeks before birth, your baby will gain around half an ounce of fat a day. When she’s ready to be born, her brain will instigate the production of hormones, which stimulate the uterus and placenta to send chemical messages that trigger your contractions.

Her amazing 40-week journey from single cell to baby is complete.

Your body Your weight gain will stabilise now and you may even lose a few pounds but the weight of your baby and the pressure on your spine can make you feel very heavy and cumbersome. Your cervix will soften and thin – known as ripening – close to your due date, loosening the mucus plug that has been sealing it. This is known as a show and is one sign that labour is imminent.

Your baby relies on the placenta for oxygen and nutrients right until the moment she takes her first breath outside the womb. During each contraction, her oxygen supply is slightly reduced as blood flow to the vessels in the uterus supplying the placenta are compressed.

To help her cope with these dips, her body releases large quantities of adrenaline to keep her heart pumping fast enough. As soon as your baby takes her first breath, her heart effectively changes from a single pump maintaining the blood flow throughout her body and into the placenta where all her oxygen and nutrients come from, to a double pump, maintaining blood flow throughout her body as well as getting blood to and from her lungs so she’s able to get her oxygen from the air.