Weeks 1 - 4
You: Blissfully unaware of what's about to happen, you get your period. Midway through your cycle, you release an egg and it starts its journey down the fallopian tube.
Your baby: Egg meets sperm, egg gets fertilised, and boom! The sex of your baby is already determined. The fertilised egg carries on towards the womb, its cells dividing all the time. Once it implants itself in the wall of your uterus, you've done it - you're pregnant!
Tip: If you're not doing so already, start taking a daily pregnancy vitamin and mineral supplement with folic acid - there's a selection of brands at all good chemists.
Weeks 5 - 8
You: Around now you'll probably pee on a stick and get the shock of your life! Whether you've been trying for ages or your pregnancy is a complete surprise, suddenly it's real and that can be a lot to take in. You might be feeling pretty sick right now, too, as all those hormones are going crazy, so try to take it easy.
Your baby:By week 8, your baby will be the size of a grape, with buds appearing that show the beginnings of arms, fingers, legs and toes.
Tip: Contact your community midwife (ask at your GP's surgery) and book in your first antenatal appointment.
Weeks 9 - 12
You: You might be trying to keep your pregnancy under wraps until you hit the 12-week mark. It can be really difficult to keep such big news a secret, but if that's your decision enjoy the excitement and this special time along with your partner.
Your baby: Your baby's bones are forming, her facial features will appear and she's growing really fast. By 12 weeks, all her major organs and structures will be fully formed, and she's around the size of a large strawberry already!
Tip: Feeling tired? Switch from white, refined foods to wholewheat bread and pasta, and brown rice, as these help to balance blood-sugar levels, which should help to relieve your fatigue.
Weeks 13 - 16
You: It's time to bask in the excitement of others when you tell them you're expecting (and the fact the sickness should start to ease off). Your heart is working harder to pump extra blood round your body, and you may feel breathless. But most women find the second trimester is the best bit.
Your baby: Your baby will be practising inhaling and exhaling and using her facial muscles. She's covered in a fine hair called lanugo.
Tip: Studies suggest your baby can react to what she hears by around week 16. Try playing her your favourite songs.
Weeks 17 - 21
You: Your foetal anomaly scan will check your baby's development and you may find out what sex it is if you choose to. Your skin may change at this time, so if it's usually dry it becomes oily, and vice versa.
Your baby: Her legs are getting longer and you may well feel those tiny fluttering kicks for the first time - a magical moment that's often mistaken for wind! She can suck, swallow and blink, and as her heart gets stronger her growth starts to slow. She's the size of a large banana.
Tip: Your appetite might be increasing but remember, you don't need extra calories until the third trimester.
Weeks 22 - 26
You: Your breasts might start to leak colostrum - your baby's first food. It's quite normal, so don't worry. You might find that your hair is especially thick and glossy - bonus time!
Your baby: By the end of this month, your baby will be roughly 23cm long and perfectly formed (if a little scrawny). The lanugo thickens and darkens, her lungs are developing and her nostrils start to open.
Tip: Snack on bananas to up potassium intake - leg cramps are common now and may be caused by a lack of potassium.
Weeks 27 - 30
You: You might notice that your bump tightens around now - these are Braxton Hicks contractions, which tone your uterus for labour. As your ever-expanding uterus presses against your stomach, you may experience heartburn, so eating little but often, and sleeping propped up with pillows, will help.
Your baby: Her eyes are open and she can suck her thumb. She has eyebrows, eyelashes and is sensitive to light, sound and smell.
Tip: Finding it hard to sleep with your growing bump? Invest in a pregnancy wedge pillow.
Weeks 31 - 34
You: Your uterus is around 500 times bigger than its pre-pregnancy size! Braxton Hicks contractions intensify and can take your breath away. If you suddenly develop a severe headache or feel very sick, call your midwife. You're at risk of pre-eclampsia now, so be sure to attend all antenatal appointments.
Your baby: Fat deposits under her skin conceal the blood vessels that were visible until now. Loose skin on her face fills out, so no more wrinkles! Her fingernails are at the end of her fingers and growing, so may need cutting soon after birth.
Tip: As your baby's bones continue to harden, make sure you get plenty of calcium.
Weeks 35 - 38
You: Have you written your birth plan? If not, do it now! But remember, things often don't go to plan, so although it's great to convey the kind of birth you want, don't be too disappointed if it doesn't happen the way you want it to.
Your baby: Your baby will start to move into your pelvis around now, and is almost ready to go. She's getting a good supply of antibodies from you via the placenta, and most of the lanugo has disappeared. But hair on her head might be up to 5cm long.
Tip: Pack your hospital bag. Include toiletries, nappies, clothes for you and the baby, maternity and breast pads and a nursing bra. Even if you plan to give birth at home, it's a good idea to have this stuff prepared in case you have to transfer.
Weeks 39 - 42
You: On your marks... get set... give birth! Many babies are overdue by up to two weeks. Still, you'll go into labour any day now. Signs to look out for are a 'show' (a bloody, gel-like substance in your knickers), waters breaking or contractions that increase in strength and frequency.
Your baby: The position your baby is lying in now is important, because she'll probably stay like this right through to birth, as space is too tight for somersaulting! If she's breech, you may be advised to consider a Caesarean.
Tip: Try to relax and rest as much as possible in the days leading up to the birth - you're going to need your strength!
If you suspect you may be pregnant here are some of the common Signs and Symptoms of Being Pregnant
Find out your babies due date and other interesting dates using our Pregnancy Calculator
www.goodtoknow.co.uk has all you need to know about health, family, food and diets.