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. There are certain foods and medicines you should avoid to keep your baby safe and healthy. You’ll also need to cut out alcohol and smoking, and cut back on your caffeine intake.

Download Your guide to a healthy diet in pregnancy here.

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.

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 your emotions in pregnancy here

Read more about The first trimester

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    First trimester trials

    Constant nausea, indescribable tiredness, aching boobs, awkward white lies...the first trimester is not always easy. In fact, it can be pretty horrendous. Here’s our survival guide to get you through the first 12 weeks.

  • Pregnant woman with GP receiving advice on how to quit smoking.

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    Quitting smoking is a challenge but there is lots of help and support out there for you.

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    Emotional changes in pregnancy

    Pregnancy brings new emotions and it can be hard for women to tell what's normal and when they should look for help.


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 21 Oct 2016 - 11:59

    Dear Tommy's, I am coming up 11 weeks and I'm so grateful for all the clear information on your website, it's so useful, thank you! A bit of minor constructive feedback on the website per se - on this page you refer to Week 10 - having a uterus the size of a man's fist, which is the last way I'd want to think about my womb right now and seems like a strange choice of words! Could you perhaps use a different analogy?
    Secondly, it looks like you mostly refer to the developing baby as "he". This strikes me as an odd default - esp for all of us who don't yet know if it's a boy or a girl at this stage. Might you consider referring to he/she, or it? It may seem like a petty detail, but it would be one way of moving away from gender bias. Many thanks for considering my feedback.

  • By Midwife @Tommys on 21 Oct 2016 - 12:54

    Hi, we always appreciate any feedback that we receive and look into every comment and suggestion that is made as we very much value the thoughts of all the users of the website. Your suggestions have been noted and will be reviewed. If you would like feedback on the action taken on your comments, and feel comfortable doing so, please do email us so we have your email address to be able to update you.

  • By Anonymous (not verified) on 20 Oct 2016 - 11:25

    Before I had my last period, I was having pain like feeling at my lower right side, only come when I cough, after the period the feeling continues , I feel feverish, food craving, slight headache e.t.c, can this be pregnant? Though im afraid to take any test.

  • By Midwife @Tommys on 20 Oct 2016 - 11:47

    Hi there.
    I would visit your GP to discuss this asap as it sounds as if you are experiencing appendicitis. If you had the pain before, during and after your last period, then it is unlikely to be due to a pregnancy.
    Lower right sided pain, with a fever especially can be a sign of fairly rapid onset appendicitis. If you are feeling very unwell, then i would bypass going to the GP and seek urgent care at a walk in centre or a&e minors. Appendicitis can be dangerous if left untreated and un-diagnosed - please seek assistance today.

  • By Anonymous (not verified) on 2 Sep 2016 - 15:02

    Grateful to God, I missed my period n decided to take a home tests which comes out Positive... I will carry d pregnancy to full term in Jesus name Amen. Praying for those believing God for dis kind of Joy..., I pray by d name that's above every other name.. the name of Jesus.. that this year will not pass u bye.

  • By Midwife @Tommys on 2 Sep 2016 - 15:54

    Many congratulations, enjoy your pregnancy and we hope all goes well

  • By Anonymous (not verified) on 7 Sep 2016 - 08:28

    Ncooh so do i believing in God, I will carry my pregnancy through out in Jesus mighty name and i thank him.. . all the women who need to get pregnant .. God is able

  • By Anonymous (not verified) on 11 Sep 2016 - 13:17


  • By Anonymous (not verified) on 11 Oct 2016 - 17:47

    amen and bless you.

  • By Midwife @Tommys on 22 Aug 2016 - 11:03

    Every woman will conceive at a different rate. Some women's bodies will take a little more time to conceive than other's as we are all made slightly differently. This is normal!
    Your Doctor who knows your full medical history will be able to better guide you in your predicted rate of conception. Best of luck!

  • By Anonymous (not verified) on 20 Aug 2016 - 11:51

    Hi,have been trying to conceive since Jan,went to my gyna and she gave me ovacare drugs,am I likely to conceive this month

  • By Midwife @Tommys on 18 Aug 2016 - 11:27

    Hi, it is difficult to give you an exact answer as women have different length cycles and I am unsure when your next period is due. If you are late then you can take a test however there is a chance that it is still a little early. If the test is negative I would suggest to wait a week and then test again. If you are trying for a baby do remember to be taking folic acid also.

  • By Anonymous (not verified) on 18 Aug 2016 - 09:49

    my last period day was on 21.07.2016. Its 29th day is today. when should i take test?

  • By Midwife @Tommys on 15 Aug 2016 - 15:13

    This pain could be caused by your expanding womb and your hormones. It can 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 13 Aug 2016 - 05:47

    Hi I'm 9 weeks and I have slight pain in my right side below my ribs above my hip. Should I be concerned. It's been 2 nights in a row, only at night.

  • By Midwife @Tommys on 12 Aug 2016 - 10:41

    I am so sorry to hear that your previous pregnancy ended in miscarriage. In this pregnancy it is very normal to be feeling more anxious and worried, there is little you can do to prevent a miscarriage. Our advice is to make sure you are taking folic acid, try having healthy balanced diet and doing some light exercise. There is lifestyle advice on our website or if you would like further advice and support then please call us 0800 0147 800 or email

  • By Midwife @Tommys on 12 Aug 2016 - 10:05

    If you have had a blood test and urine test showing positive for pregnancy then this would indicate your hormone levels are sufficiently raised and you are pregnant. If they could not see any thing on scan in your womb it may be that it is a little early, have they offered you a follow up scan at all? If not I would suggest contacting your GP or EPU to discuss this. In the mean time if you have any one sided abdominal pain, shoulder tip pain, feel dizzy or unwell or have any bleeding then please be seen at the hospital as soon as possible.

  • By Anonymous (not verified) on 11 Aug 2016 - 10:50

    Hi I'm worried as I had a miscarriage at 5 weeks and now after one cycle think I may be pregnant again what can I do to prevent having another early miscarriage or what should I avoid

  • By Anonymous (not verified) on 11 Aug 2016 - 10:11

    hiii! i am pregant i did test at home it shows positive i go to hospital they did blood PT wich is more sensitive is also positive but when they scan they didnt see any thing in the womb.

  • By Midwife @Tommys on 9 Aug 2016 - 11:43

    Hi I'm sorry you are in pain and worried about your pregnancy. Please give us a call on the PregnancyLine 0800 0147 800

  • By Midwife @Tommys on 8 Aug 2016 - 14:52

    It's perfectly safe to have sex during pregnancy. Your partner's penis can't penetrate beyond your vagina into your cervix.
    As long as you do not have any history of early miscarriages , or recent episodes of bleeding., intercourse in the first trimester is absolutely fine!

  • By Anonymous (not verified) on 7 Aug 2016 - 07:16

    My wife is pregnant this the 1st month so we can continue unter corse and untill how many months we can inter corse without any harm of baby.

  • By Midwife @Tommys on 2 Aug 2016 - 11:44

    Yes. A positive pregnancy test means that the pregnancy hormone, HCG is present in your urine. This hormone is present once you have conceived. Some pregnancy tests can be taken several days before your period is due – but the earlier you take the test, the less reliable the result. To have a more accurate result, take the test at least a week after your period would have been due

  • By Midwife @Tommys on 2 Aug 2016 - 11:24

    As long as you do not have any history of early miscarriages , or recent episodes of bleeding., intercourse in the first trimester is absolutely fine!

  • By Anonymous (not verified) on 31 Jul 2016 - 10:49

    hi I m pregnet now my first month I wan ask some think during 1 month pregnancy can we do inter sorce

  • By Anonymous (not verified) on 29 Jul 2016 - 18:43

    Hi I last had my period on 11 July and lasted four days but since last week been feeling tired and exhausted so did a pregnancy test came back positive is it possible that I am pregnant before my actual next period came?

  • By Midwife @Tommys on 29 Jul 2016 - 16:22

    Our advice is to take any pregnancy test as a positive, tests do have slightly different sensitivity. I would suggest to wait a week and repeat the test. Or else you can go back to the GP and ask for a blood test which is more sensitive and accurate. In the meantime I would suggest to start taking folic acid and vitamin D supplement if you have not already and be aware of foods to avoid in pregnancy in case you are pregnant.

  • By Anonymous (not verified) on 29 Jul 2016 - 16:12

    I had a positive test at home so i sent a urine sample to the doctors but it came back negative the day i got told it was negative i done another test at home and it was positive again what should i do

  • By Midwife @Tommys on 26 Jul 2016 - 15:34

    The recommended time is the day after you have missed your next period as being the most accurate time , although there are some tests on the market that state they can give an earlier result

  • By Anonymous (not verified) on 26 Jul 2016 - 02:27

    When will it be a good time to test

  • By Anonymous (not verified) on 13 Jul 2016 - 10:45

    Wow, I'll learn a lot from this website.
    Keep it up guys.

  • By Anonymous (not verified) on 5 Jul 2016 - 07:47

    Very informative and nice information indeed

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