First trimester: weeks 1 to 12

The first weeks of your pregnancy are a vital time as your pregnancy gets established. While you get used to being pregnant, your body is busy building a baby!

Weeks 1-12 infographic

First trimester: key stages

The first trimester begins on the first day of your last period and lasts until the end of week 12. This means that by the time you know for sure you're pregnant, you might already be five or six weeks pregnant!

A lot happens during these first three months. The fertilised egg rapidly divides into layers of cells and implants in the wall of your womb where it carries on growing. These layers of cells become an embryo, which is what the baby is called at this stage.

During this trimester, your baby grows faster than at any other time. By six weeks, a heartbeat can usually be heard and by the end of week 12, your baby's bones, muscles and all the organs of the body have formed. At this point, your baby looks like a tiny human being and is now called a fetus. He or she will even be practising swallowing!

Lifestyle changes in the first trimester of pregnancy

You may need to make some lifestyle changes now that you are pregnant. Find out which foods and medicines you should avoid to keep your baby safe and healthy here. You’ll also need to cut out alcohol and smoking, and cut back on your caffeine intake.

Get your free guide to healthy eating straight into your inbox.

Try not to worry if you smoked or drank alcohol before you found out you were pregnant. Now that you know, you can take steps to look after yourself and your baby.

Get help to stop smoking here.

You can also find lots of useful tips on coping with everyday pregnancy niggles such as morning sickness, cramp or indigestion.

Don't forget your mental health as well as your physical health! It's normal to feel some anxiety and stress but it shouldn't be ongoing.

Find out more about emotional changes in pregnancy here.

Find out more about the first trimester


1. NHS Choices (2012). “Your pregnancy week by week”. National Health Services: Choices. Accessed online on 02.02.2015: Page last reviewed: 22/07/2014. Next review due: 22/07/2016

2. Macdonald S, Magill-Cuerden J (2012) Mayes’ Midwifery, 14th edition, London, Ballière Tindall

3. NICE (2008). “Antenatal care: NICE clinical guideline 62”. National Institue for health and care excellence 2008; accessed online on 15.01.2015: (last review August 2014). 

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Last reviewed on April 1st, 2015. Next review date April 1st, 2018.

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  • By Anonymous (not verified) on 27 Feb 2017 - 08:13

    hello.. my last period was on 25th jan 2017.. its been a month bt i havnt got my periods yet.. me n my hubby had intercourse on 7- 8-9-10 of this month... shud i go for a home pregnancy test?? or is it too early ??

  • By Midwife @Tommys on 27 Feb 2017 - 11:46

    Hi there.
    Using your last menstrual period date of 25th jan, and presuming you have a 28 day cycle, it is possible that you are approx 3 weeks pregnant and this would show up on a pregnancy test if you are pregnant. So it is worth going out and buying a home test. Some tests are more sensitive than others, so waiting another few days may be sensible in order for your pregnancy hormones to increase and show in your urine.
    Take care and good luck!

  • By Anonymous (not verified) on 26 Feb 2017 - 10:01

    hello am 8weeks pregnant but i have alot of pain in my stomach i was given medicines like paracetamol n bascopan but there is no change... i dont feel like eating anything i only take porridge..... the náusea is very strong even after taking medicine for it.... what should i do please

  • By Midwife @Tommys on 27 Feb 2017 - 10:27

    Hi there.
    Any abdominal pain, at any gestation of pregnancy, needs to be investigated as soon as possible. It would be a good idea for your GP to refer you to your local early pregnancy assessment unit so that you can have an abdominal scan and bloods taken to ensure the pregnancy is healthy. If your pain is incredibly severe, then you should go to a&e urgently in case the pregnancy is ectopic (growing in your Fallopian tube) which can cause a lot of abdominal pain and is incredibly dangerous to your health.

    Pregnancy nausea is very common and can come and go throughout pregnancy. There are various simple ways that you can try to ease the nausea. Have a look on our webpage for some helpful tipss to hopefully help you.

    Please look after yourself!

  • By Anonymous (not verified) on 26 Feb 2017 - 09:23

    I found out I'm pregnant the 14 Jan 2017 when I was 3 weeks pregnant and I used two home tests got the same answer positive. I got my period the 9 of Feb for two days was abnormal flow and just dissaper. now I'm worried I lost this baby

  • By Midwife @Tommys on 27 Feb 2017 - 10:00

    Hi pregnancy mom
    It would be sensible for you to visit your GP asap to do another pregnancy test and to refer you to your local early pregnancy assessment unit if there is some concern about bleeding in early pregnancy. They may wish to take some bloods from you, and do an ultrasound scan to determine the gestation and health of the pregnancy. Please look after yourself.

  • By Anonymous (not verified) on 26 Feb 2017 - 08:02

    Hello, I have just found out I am expecting. Not really sure how far I am, I am going to the doctor this week, will they be able to tell me how far I am?
    I have been drinking alcohol and eating rubbish like sweets and chocolate and I feel terrible about it. I've cut it all out now since Friday but will this have done damage?

  • By Midwife @Tommys on 27 Feb 2017 - 09:54

    Hi Mjones
    Many women have exactly the same concerns as yours when they first find out that they are pregnant. Drinking alcohol in the early stages of pregnancy is something that many women worry and feel guilt about, but it is both unknown, yet unlikely to have caused any problems for the growing fetus. It is best that you completely cut out alcohol from now on. The occasional sweet treat like chocolate is not bad for pregnancy, everything in moderation is sensible. Please have a look at our webpage on diet during pregnancy so you can see what types of food and quantities are great for a healthy pregnancy.
    When you go to the doctor, they will ask for the date of the first day of your last menstrual period, to give an estimation of how many weeks you are. Then you will be referred for midwifery care and for your first ultrasound appointment where the gestation of your baby will be more accurate and an estimated due date will be given to you too. Please take care of yourself.

  • By Anonymous (not verified) on 18 Feb 2017 - 19:31

    pls help, I went to ultrasound scan and the doctor confirmed am 11 weeks pregnant and 3 days. but he said that I will put to bed on 27th June 2017. How possible it is. pls adivice

  • By Midwife @Tommys on 20 Feb 2017 - 09:34

    Hello and Congratulations on your pregnancy,
    Your message is a little unclear - please email on midwife@tommys.og or call our Pregnancy information line on 08000147800 for further advice.

  • By Anonymous (not verified) on 17 Feb 2017 - 18:07

    I'm abt 6weeks pregnant and I have dis abdominal pain and back pains as well not DAT painful but it makes me feel kinda awkward......and I have dis bitter taste in my mouth ...and m getting sick of DA pills m drinking

  • By Midwife @Tommys on 20 Feb 2017 - 09:45

    Congratulations on your pregnancy!
    I'm sorry you are experiencing lower back and abdominal pain - it is not unusual to experience some period like cramps in early pregnancy, but if they are painful, becoming more severe or causing you concern please contact your GP for a check up.

  • By Anonymous (not verified) on 16 Feb 2017 - 08:39

    I don't know how long i am, I'm pregnant and i have pain in my spanielccord please help is it normal? I tested pregnant on the 27/01/2017 and it was positive, on the 2/02/2017 i was bleeding on the 7/02/2017 it stopped until now and on the 13/02/2017 i tested it positive do you think it's normal?

  • By Midwife @Tommys on 16 Feb 2017 - 11:25

    Hi, I can understand your confusion and would suggest that if you have a positive pregnancy test on 13th that you see your GP. You may be referred to an early pregnancy unit for a scan and/or a blood test which will confirm whether or not you are pregnant.
    Hope this helps.
    Tommy's midwives

  • By Anonymous (not verified) on 16 Feb 2017 - 03:42

    Some few I did a PT In the lab n it showed positive But very faint line . I had alot of pain like cramp for over a week. Then I saw blood flow for 2days. I got worried although it's less than my normal flow. I tried doing a home test after d flow it's been negative. Should b worried? Been having headaches for a while. D pain down my abdomen has reduce. Pls am still pregnant.

  • By Midwife @Tommys on 16 Feb 2017 - 12:42

    Hi-Unfortunately it sounds like you have had a very early miscarriage. However if your abdominal pain continues or gets worse , it may be a good idea to see your GP.

    Hope this helps and do contact us if you have any other concerns

  • By Anonymous (not verified) on 16 Feb 2017 - 02:08

    Hello, I have been dizzy for about two and a half months now. I was always worried about what it was but tried to just wait for it to go away. For the passed two months I have experienced headaches daily and am nauseous every once and awhile. I started to develop a cough and some sinus drainage so I went to the doctor and they told me this is where the headache and dizziness are coming from and gave me antibiotics for a sinus infection. Two antibiotic doses later, the dizziness is ongoing. I have recently noticed my nipples have darkened and I almost fainted today. I have taken a few at home pregnancy tests and they all came back negative. I would have conceived November 5th. Is it safe to say it is time to get a blood test or could there be something else going on?

  • By Midwife @Tommys on 16 Feb 2017 - 11:35

    Hello, I am sorry to read that you have been feeling unwell. I would suggest that if this is on-going that you see your GP again. If your pregnancy tests are negative, this is because the pregnancy hormone hCG is not present in your urine and indicates that you are not pregnant. I hope you find some answers. Best wishes

  • By Anonymous (not verified) on 15 Feb 2017 - 17:43

    I've recently found out I am pregnant! I had the implant out on the 10 Jan 2017, tested on 7th Feb and it came up positive! Checked a few more times and all positive. Anyway I just wanted to know how to date this pregnancy? Would it be the day my implant was taken out? I am a bit worried about getting pregnant so quick after implant removal, just hoping it all goes ok.


  • By Midwife @Tommys on 16 Feb 2017 - 12:18

    Hi. There is no reason to be concerned about getting pregnant so soon after your implant was removed, but your GP may advise that you are seen in the early pregnancy unit in order to date the pregnancy. Best wishes from Tommy's midwives

  • By Anonymous (not verified) on 15 Feb 2017 - 06:37

    I have just found out im expecting but i keep getting pains in the lower part of my stomach almost like period pains is this normal

  • By Midwife @Tommys on 15 Feb 2017 - 13:24

    Congratulations on your pregnancy!
    I'm sorry you are experiencing lower abdominal pain - it is not unusual to experience some period like cramps in early pregnancy, but if they are painful, becoming more severe or causing you concern please contact your GP for a check up.

  • By Anonymous (not verified) on 9 Feb 2017 - 13:32

    Hi, I'm only 6 weeks and I've been in a lot of pain and feel like I'm going to pass out in the morning only due to have diarrhoea. Just want to know if this is normal. Has anyone had symptoms like this?

  • By Midwife @Tommys on 9 Feb 2017 - 15:31

    Hi. Sorry to hear that you are feeling unwell. Diarrhoea can be very distressing. Best advice is to ensure that you are drinking plenty to avoid becoming dehydrated and ensure that you wash your hands after going to the toilet. It is unlikely to cause a problem for the baby but if it persists beyond 48hrs, please see your GP. Regarding your pain, you don't say where this pain is. Please feel able to contact the midwives on 0800 0147 800 to discuss. Best wishes and we hope you feel better soon.

  • By Anonymous (not verified) on 9 Feb 2017 - 08:39

    Hi, im 6 weeks pregnant and last night when I laid down and touched my belly, I felt this weird lump about 2 inches away from the hip bone. The lump it's not painful in particular(sometimes on that side I feel a mild sharp pain that last 2 seconds) and it's about 6 cm long and feels quite thin. I don't have any bleedings or pain except some mild cramps on my lower abdomen. I'm very worried about this lump because (maybe sounds stupid) I'm afraid not to be an ectopic pregnancy. My appointment with my GP is in a few days, but this lump is keeping me worried. Can you please tell me what it might be? Thank you

  • By Midwife @Tommys on 9 Feb 2017 - 12:32

    Hi Congratulations on your pregnancy. There may be many reasons for this lump and it may go away on its own before you see your GP. It is reassuring that you don't have any pain or bleeding. If your symptoms change and you have pain or bleeding please see your GP or Early pregnancy unit.

  • By Anonymous (not verified) on 7 Feb 2017 - 16:32

    Only few days ago I found out I'm pregnant. Doing my calculations I should be about 5-6 weeks. What is concerned me is some quite mild cramps in my lower abdomen I'm feels them for the past few days. They aren't continuous, they start mostly when I standing up or working for few hours, but if I'm laying down they go away. I don't have any bleeding or back pain. I'm know the pains might be normal for the changes in my tummy, but I'm just worried not to be a sign of a miscarriage as I really wish to have this baby. I already made an appointment with my gp, but it's gonna be in two days, and the time it's absolutely killing me. Thanks for your help

  • By Midwife @Tommys on 7 Feb 2017 - 16:39

    Congratulations on your pregnancy!
    The pain you are describing could be caused by your expanding womb and your hormones. It can sometimes feel like a ‘stitch’. You may also feel light period-like discomfort at the beginning of a pregnancy. These symptoms may be nothing to worry about. However, if you are having persistent abdominal/stomach pain, it should be checked by a doctor or midwife immediately.

  • By Anonymous (not verified) on 5 Feb 2017 - 07:43

    hi,can you kindly calculate my due date my first date of the last period was on 14th november 2016

  • By Midwife @Tommys on 6 Feb 2017 - 10:20

    Using our pregnancy calculator (- see below on our webpage), presuming you have a regular 28 day cycle with a last menstrual period date of 14th Nov 2016 - you would be due on the 21st August 2017.

  • By Anonymous (not verified) on 2 Feb 2017 - 15:20

    Hi. Am 5weeks and 2 days pregnant. But I know I saw my period in December 2016 but can't remember the date. But I had sex twice in this same month 23rd and 30th respectively. Pls can u calculate and tell me which of this dates I took in. Reply

  • By Midwife @Tommys on 2 Feb 2017 - 16:12

    Hi, If you are 5 weeks plus 2 days today then conception would be around 9th January (plus or minus 3-4 days either side).
    For a 28 day cycle that would make your last period around 26th December. Hope that helps

  • By Anonymous (not verified) on 31 Jan 2017 - 03:33

    What causes bleeding at 8 weeks of pregnancy or do having sex during pregnancy causes bleeding.

  • By Midwife @Tommys on 31 Jan 2017 - 09:44

    Hello - bleeding in the early stages of pregnancy can be caused by a number of things, including after having sex. It is important that you are seen by a dr asap - please see your GP regarding your bleeding.
    Wishing you all the best

  • By Anonymous (not verified) on 28 Jan 2017 - 08:28

    Worried I'm not sure how long I'm I pregnant because I never see my period for a year,I went to the clinic they confirm that I'm pregnant but they can't feel the baby yet,I'm I early or wht

  • By Midwife @Tommys on 30 Jan 2017 - 10:04

    Hi Fredy
    It is difficult to know how pregnant you are without being able to identify the first day of your last menstrual period However, an ultrasound scan is only able to see a pregnancy over 4-5 weeks gestation. So, you will need an ultrasound scan to determine the size of the fetus so that they can give you an estimation of how many weeks pregnant you are and potentially when you might have conceived. So please go back to the clinic and undergo further testing.

    All the best.

  • By Anonymous (not verified) on 22 Jan 2017 - 22:02

    Hi I had c section in 2007 then normal birth in 2009 then c section again in 2013 wot r my chances of having normal birth?

  • By Midwife @Tommys on 23 Jan 2017 - 10:09

    Hi there.
    Having had two c/s and one vaginal birth puts you in a position of weighing up your options. With your obstetric consultant, you can have a discussion about your medical and pregnancy history and evaluate if a vaginal birth would be safe to attempt. The reason for your previous sections, as well as how your vaginal birth progressed would all be assessed along with your personal and pregnancy risk factors.
    Don't rule out either one just yet, but there is certainly a discussion to be had and a decision to be made. Take care!

  • By Anonymous (not verified) on 20 Jan 2017 - 20:42

    I had my last period on the 17th of December and have not see it dis month

  • By Midwife @Tommys on 23 Jan 2017 - 10:03

    Hi there. It would probably be best to do a pregnancy test at home or at your GP's to confirm if you are pregnant or not. Then your estimated due date and current gestation can be roughly estimated.

  • By Anonymous (not verified) on 17 Jan 2017 - 14:37

    My youngest daughter was born 3/14/16 I got the nexplanon put in 3/19 or 3/20 I had it taken out 11/29/16 I go my period a week before I got it taken out. Then on 12/2/16 I had anothe period. Then on 12/22/16 I had what I thought to be a very weird period. It was bright red and when I stood up I would drip down my legs. It last the same length as my regular period but ir seemed to be alot of blood bright red and smelled like iron. Well i was suppose to get my period on the 15 of this month ive had alot of cramping worse then period cramps and still not pregnant. Ive taken two hpt both said negative. Coud I be pregnant ? This is not my first kid but with my last pregnancy It took me I think 2 months to get a positive pregnancy test, without a period. But witb my first two I got a positive right after missed period.

  • By Midwife @Tommys on 17 Jan 2017 - 14:43

    Thank you for your query. I would need a few more details from you in order to help with your question, please email with your query so we can help answer your questions.

  • By Anonymous (not verified) on 16 Jan 2017 - 19:58

    For nearly 5 years I yearned to bare my husband's first child, having 3 boys from a previous marriage. I was worried I would become too old or other issues were preventing pregnancy but as time went on my husband told me we have plenty of time. So I literally dropped the idea after a tragic incident with my oldest son a baby was definitely out of my head. Being as though everything had been so overwhelming we went from actively being intimate to maybe 1-2 a week. A little over a month ago I had nausea and told him I felt sick, did not relate it to pregnancy until too many other signs appeared. My breasts were just so sore and swollen, felt very bloated and I assumed a bad menstrual cycle was coming. Well, I continued to wait for my cycle and as I got into January I really started to question when my last cycle was. Something told me to take a test and sure enough I did and it was positive. Because I was in disbelief I did take 4 more, all of which were positive with one stating: PREGNANT. Of course it was excitement and took a lot of the stress and overwhelming feelings away because I know how important the first stages are so I am completely humbled for the first time this year. I know it will take some time to see a Doctor but I feel horrible because I do not recall the date of my last menstrual cycle, I tried to find the receipt when I had purchased pads, trying to relate to certain times and or dates in the last few months I cannot recall with everything that has happened. Since that test I swear every feeling: emotions, hormones, sensitivity- you name it has been heightened or I am just more aware of the symptoms, i do not know. So now I have become obsessed this weekend with the question, How far along could I be? DRIVING me crazy. I am showing, breast are swollen and sensitive, my nose looks a little swollen, my fingers have swollen a little, my abdomen is tender to tight clothing and my "V" is even enlarged a little. What's worse is it seemed my belly was harder and rounder yesterday and now softer so I am so concerned and confused.. Can I still be within the first trimester? or possibly twins since so fast? So lost and had to find some answers. Loved this site so I had to leave.. and sorry so long

  • By Midwife @Tommys on 17 Jan 2017 - 12:14

    Congratulations on your pregnancy! This sounds like a very much wanted and wished for baby and a wonderful surprise too.
    One of the first things you should do is contact your GP so that they can refer you for antenatal care and determine how pregnant you are. If you are unsure of dates, discuss this with your GP and they maybe able to arrange an earlier scan.
    It is also important to ensure you start taking Folic Acid and Vitamin D as soon as possible, you can buy both from your local pharmacy who will be able to advise further.
    If you would like to discuss anything further please call us on our Pregnancy Line: 08000147800 or email us at

  • By Anonymous (not verified) on 15 Jan 2017 - 16:16

    Hi i just found out im pregnant my last period on 16 December how far am i now

  • By Midwife @Tommys on 16 Jan 2017 - 09:32

    Hi there. For ease in working this out, You can use our pregnancy calculator on our website. You will need to know the date of the first day of your last menstrual period and roughly how long your cycle is.

  • By Anonymous (not verified) on 12 Jan 2017 - 10:51

    Breast pain and heavy my results is positive
    Breast pain common in pregnancy
    Dis is my 1st pregnancy

  • By Midwife @Tommys on 12 Jan 2017 - 11:08

    Congratulations on your pregnancy! Yes pregnancy can bring about changes to the breasts even early on. We always recommend to wear a well fitted bra and check your breast for changes and any lumps throughout your pregnancy, if you have any concerns then speak to your midwife or GP.

  • By Anonymous (not verified) on 6 Jan 2017 - 14:54

    Keep up your good work mummy Tommy! Please my last period was on October25 till now and I was confirmed positive after a blood test please how many months could the babe be now?

  • By Midwife @Tommys on 6 Jan 2017 - 15:21

    Many congratulations on your pregnancy!
    If you have a normal 28 day menstrual cycle then your due date will be about the 1st of August. When you have your first scan they will give you your official due date that will be used for the rest of the pregnancy. If your cycle is different to this you can use our pregnancy calculator to estimate your due date:

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