Miss Chrissie Yu’s guide to your pregnancy

Week by week – what you can expect for you and your baby; from conception to birth.

By Miss Chrissie Yu MBBS (Lond.) MD (Lond.) FRCOG
Consultant in Obstetrics & Fetal Medicine
First published March 2023

Pregnancy is a natural process and different for every woman. Here’s a quick guide to what you can expect week-by-week during your pregnancy.

1st Trimester

Week 1-2

You: Pregnancies are dated from the first day of your last period. Strange as it may seem you may not be pregnant for the first week or two of your pregnancy!

Baby: There’s no embryo yet — just an egg and millions of sperm getting ready for action.

Week 3

You: The fertilised egg travels along your fallopian tube and implants in your womb. This can cause spotting; tiny blood spots.

Baby: An embryo about 1mm across is now a bunch of cells that are growing and multiplying.

Week 4

You: Pregnancy hormones can cause early symptoms such as breast tenderness and nausea. These can also be confused with your pre-menstrual symptoms. Your body is beginning to form the placenta and amniotic sac

Baby: Protect baby’s unborn brain! Taking 400 micrograms of folic acid daily in early pregnancy can reduce baby’s risk of neural tube defects by up to 70%.

Week 5

You: As soon as you miss a period you can take a pregnancy test.

Baby: The embryo is starting to look more like a fetus and its heart and circulatory system are developing.

Week 6

You: Don’t worry, food cravings are very common in early pregnancy. Make sure you eat well – and healthily – throughout your pregnancy.

Baby: Baby’s head is taking shape, and its cheeks, chin and jaws are beginning to form.

Week 7

You: Fatigue and mood swings are very common in the early stages of pregnancy and can go on for a few months.

Baby: Baby is growing fast and creating new brain cells – about 100 per minute!

Week 8

You: You may be drinking – and needing to pee – more often.

Baby: Baby is growing at a rate of a millimetre a day and its lips, nose and eyelids are forming.

Week 9

You: Morning sickness can be a challenge in early pregnancy.

Baby: The fetal heartbeat can be heard on a Doppler device at your ante natal appointment.

Week 10

You: Tummy cramps, spotting and vaginal discharge are common.

Baby: Tiny teeth bumps are now developing under baby’s gums. Bones and cartilage are now forming; knees, ankles and elbows are starting to take shape.

Week 11

You: You may notice a slight baby bump beginning to appear.

Baby: Fingers and toes are now looking like the real thing. Fingernail and toenail beds are growing.

Week 12

You: Make sure you’ve booked your Nuchal Scan before weeks 10-12.

Baby: Baby’s tiny intestines are now moving back into the abdomen.

Week 13

You: Some of the earlier symptoms of pregnancy such as morning sickness can recede, but new symptoms such as – may appear.

Baby: Baby’s eyelids are shut to protect the eyes as they develop. Vocal cords are forming, and baby’s head is about half the size of its total body.

2nd Trimester

Week 14

You: You’re now in the second trimester of your pregnancy.

Baby: Fully developed genitals appear but may be tricky to detect on an ultrasound. Baby’s head, eyebrows and body start growing some hair.

Week 15

You: Perhaps book a pregnancy massage if your bump is feeling itchy and a bit stretched. Time for some maternity clothes shopping?!

Baby: Baby’s ears and eyes appear on baby’s face and head.

Week 16

You: Ultrasound scans can identify if baby is a boy or a girl.

Baby: Even though they’re closed, baby’s eyes are making small movements and can detect some light.

Week 17

You: As your womb moves upwards, your bump will be getting more noticeable.

Baby: Baby’s ears are close to being fully formed and starting to be able to hear your voice.

Week 18

You: Back pain can be more common now.

Baby: A female’s fallopian tubes and uterus are now in position. Male genitals may be visible on ultrasound.

Week 19

You: Perhaps you can feel baby moving?

Baby: You may be able to feel baby move for the first time this week, but don’t worry if you don’t. Also – baby’s lungs and main airways are developing.

Week 20

You: Time for your Anomaly Scan.

Baby: At 20 weeks pregnancy, baby weighs about 280g and has a height (crown to rump) of about 160mm.

Week 21

You: In the second half of pregnancy and you may feel baby kicking and stretching more. Stretch marks can appear as your tummy gets bigger.

Baby: Baby’s arms and legs are in proportion now and movements are more coordinated. We now start measuring from crown to heel rather than crown to rump.

Week 22

You: Talking or singing to your bump is a great way to bond as baby will hear your voice.

Baby: Baby’s ears are beginning to hear and process sounds like your breathing, your rumbling tummy, your heartbeat. Baby’s developing nervous system means those fingers are learning to grab those tiny ears, nose and umbilical cord.

Week 23

You: Stretch marks may noticeable now as there’s a major growth spurt this week, and baby will likely double in size over the next month or so. And with those pregnancy hormones on overdrive, you may start noticing that foggy, hazy feeling sometimes called “pregnancy brain!”

Baby: Baby’s arms and legs are punching out more now – you might even see them push your tummy! The placenta transfers oxygen and nutrients to baby and removes waste products.

Week 24

You: Tiny spots of colostrum discharge may appear, and your bra size may have increased by a couple of cup sizes. Your tummy button may also pop out; it’ll return to normal after baby’s delivery. Your uterus is about the size of a football and you may now have the baby bump you’ve been imagining since you conceived.

Baby: Baby’s putting on more and more weight from accumulating baby fat along with growing muscles, organs and bones. Baby’s hearing is rapidly advancing, which means if he or she frequently hears a certain song now, she’s likely to recognize it and feel calmed by it when they’re born. Baby’s nose and lungs are becoming more functional now in preparation for life after birth!

Week 25

You: Braxton-Hicks contractions may start. Your uterus is about the size of a football and you may now have the baby bump you’ve been imagining since you conceived.

Baby: Baby’s hearing is rapidly advancing, which means if he or she frequently hears a certain song now, she’s likely to recognize it and feel calmed by it when they’re born. Baby’s nose and lungs are becoming more functional now in preparation for life after birth!

Week 26

You: Keep moving to prevent stiff joints, aches and cramps. You may struggle more with insomnia and clumsiness as your tummy continues to grow.

Baby: Baby continues to work hard swallowing amniotic fluid this week. This process is essential for healthy lung development.

Week 27

You: This is a good time to plan for the birth. If you’re feeling unusual movements in your belly, it may be hiccups. As baby’s lungs continue to develop, chances of hiccups increase.

Baby: Baby’s started to develop muscle tone from all that kicking, rolling and punching he’s doing.

3rd Trimester

The third trimester is a good time to read and even sing to your baby — or rather, your tummy — and a good chance to start memorizing those nursery rhymes and lullabies you’ll need to be repeating and repeating soon. Your partner might be able to hear baby’s heartbeat by pressing an ear to your stomach.

Week 28

You: You’re entering the third trimester of your pregnancy. dealing with common week 28 symptoms like back pain and sciatica.

Baby: Fetuses often stick out their tongues at this age; possibly tasting your amniotic fluid.

Week 29

You: Your tummy button might start to stick out a bit more than usual as your womb is getting a bit cramped. Those hard kicks you were feeling will be more like jabs and pokes now.

Baby: Baby is continuing to hiccup; you’ll feel delicate, rhythmic taps to which aren’t uncomfortable for baby either.

Week 30

You: Sleep on your left side for better blood flow. At 30 weeks of pregnancy your bump may be popping even more now. A big part of that growth is in baby’s rapidly developing brain.

Baby: The surface of baby’s brain begins to wrinkle — called convolutions — so that it can hold more brain cells. Baby’s hands are now fully formed, and fingernails are growing. In ultrasounds, you may catch baby grabbing a foot.

Week 31

You: Your balance may be a bit wobbly, and your joints may be looser so do take extra care when moving around. You may be needing to visit the bathroom more often and feeling tired quicker these days.

Baby: All baby’s major organs are fully developed now, except for the lungs. So even if you gave birth this week, baby would probably do just fine.

Week 32

You: You may find it’s harder to breathe as your womb starts pushing upwards to your lungs as baby grows. And you may experience a bit of practice – in the form of Braxton Hicks contractions ahead of the day you go into labour.

Baby: Baby’s putting in longer stretches of rest, specifically REM sleep. Want to wake him up? Eat or drink something sweet.

Week 33

You: Your hair could be looking particularly glossy and healthy. By now, baby’s reached the length he’ll measure at birth, but is still busy putting on about 1000g a week. You may notice this rapid growth in the form of sharper kicks and shortness of breath, thanks to crowding around your lungs.

Baby: The plates of bone in your baby’s skull are still fairly pliable, which makes it easier for him to squeeze down the birth canal. By now, baby’s drinking up to a pint of amniotic fluid a day to help prepare the gastrointestinal system for birth.

Week 34

You: Your breasts may be feeling heavier and needing more support. Treat yourself to a new bra or two.

Baby: Baby closes its eyes when they snooze and opens them when awake, helping to settle into a sleep schedule.

Week 35

You: When sitting or lying, try changing positions to ease aches and pains caused by pressure or your baby’s movements. Your body is also in prep mode: You may feel Braxton Hicks as your uterine muscles prep for the big day.

Baby: With one month left to go baby may be starting to plan ahead by shifting to the heads-down position.

Week 36

You: You may be finding it harder to sleep or get comfortable. On the plus side this final month may bring extra joint flexibility and less pelvic pain as loosening and softening hormones kick in ahead of labour.

Baby: He or she looks more like an infant this week, with chubby legs and pink skin — even in babies of colour because of the blood vessels just beneath the skin.

Week 37

You: At your next antenatal appointment, Dr Chrissie will check your cervix for clues about how you’re progressing. As baby starts to drop down into your pelvis, symptoms such as constipation and heartburn can improve, but you may feel more pressure on your bladder.

Baby: If baby was born this week, he’d still be early term but will be full-term by week 39. He’s practicing for birth by inhaling and exhaling amniotic fluid, blinking and turning from side to side. Baby now has way more dexterity in its fingers and can now grasp onto smaller objects, like a toe or nose.

Week 38

You: Make sure you’re getting plenty of rest whenever you can.

Baby: Baby’s eyes now are blue, grey or brown. Once they’re exposed to light, they may change colour or shade. By the time your baby turns one, you’ll know their true colour. The fine downy hair that covered baby’s body for warmth is falling off in preparation for delivery. Baby’s lungs have strengthened and the vocal cords have developed, which means she’s ready to communicate through wails and cries.

Week 39

You: Be aware of the signs of labour. At 39 weeks, you’ll want to watch out for signs of labour and get that hospital bag packed, if it isn’t already.

Baby: Baby’s considered full-term now that month 9 is nearly done. Although baby’s unaware that you’re expecting his arrival, you can relax in the knowledge that he’s reached or is close to his birth weight.

Week 40

You: At 40 weeks pregnant, you’re at the official end of your pregnancy. Babies are often born a week or two early or late. Your placenta is still providing the antibodies baby needs to fight off infections for the first six months of life. If you plan on breastfeeding your milk will provide more antibodies to boost the immune system. Colustrum is a thin, yellowish prelude to breast milk that’s super rich in antibodies and feeds your baby for the first few days after delivery.

Baby: Baby is fully prepped for life outside the womb, with all systems – including organs and reflexes and lungs– go.

For more information or to make an enquiry click here or call:

Private Pregnancy Care +44 (0) 20 7486 2388
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