First trimester: weeks 1 to 12

You're pregnant: congratulations! 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. How exciting!

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 reduce your caffeine intake.

You might be surprised to learn that caffeine is not just found in coffee, but also in tea, chocolate and energy drinks! You can find out how much caffeine is in your daily diet here.

Get your free guide to healthy eating straight to 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 looking after yourself and your baby.

Get help to stop smoking here.

We also have lots of useful tips for coping with everyday pregnancy niggles. It’s common for women to experience symptoms such as morning sickness, cramp and indigestion during the first trimester. But try not to worry, these symptoms mean that your baby is growing strong and healthy!

Don't forget that your mental health is just as important as your physical health. It's normal to feel some anxiety and stress but it shouldn't be ongoing. If what you’re feeling isn’t normal for you, talk to your GP or midwife about it. They are there to help. 

Read more about mental wellbeing in pregnancy.

Find out more about the first trimester

Sources

1. NHS Choices (2012). “Your pregnancy week by week”. National Health Services: Choices. Accessed online on 02.02.2015: http://www.nhs.uk/conditions/pregnancy-and-baby/pages/pregnancy-week-by-week.aspx#close 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: http://www.nice.org.uk/guidance/cg62/resources/guidance-antenatal-care-pdf (last review August 2014). 

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

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Comments

  • By Midwife @Tommys on 26 Apr 2017 - 09:38

    Hi please get back in contact if you need advice as your message is incomplete.
    Tommy's Midwives

  • By Anonymous (not verified) on 25 Apr 2017 - 09:04

    I had my last period on 25th March and unprotected sex on de 6th of April. I took post in or 2 after twelve ours . I've had a posi

  • By Anonymous (not verified) on 24 Apr 2017 - 10:44

    I m pregnant and uts my 6 week bt i m not having any splecial feeling like vomiting. Is it ok wid my pregnancy

  • By Midwife @Tommys on 24 Apr 2017 - 13:23

    Congratulations on your pregnancy.
    Every woman id different and experiences pregnancy differently. For some that means a lot of nausea and vomiting and for some none at all. Try not to worry - you may be one of the lucky ones to not get the nausea and vomiting, or you may find that as the pregnancy progresses you start to feel it.
    Enjoy your pregnancy and if you haven't already start taking Folic Acid and Vitamin D supplements as well as visiting your GP or midwife for antenatal care and advice.

  • By Anonymous (not verified) on 23 Apr 2017 - 10:22

    My depo provera wore off before my next injection was due , I had my period and was just wondering if there is any chance I could be pregnant , I've been feeling dizzy and feeling sick all day for the past week and I passed out once . I had my injection on the 18/4/17 , if I am pregnant can the injection harm the baby ??
    Thanks

  • By Midwife @Tommys on 24 Apr 2017 - 09:54

    Hi - thanks for your message.
    Its difficult to say if you are or aren't pregnant without a positive pregnancy test. Please visit your GP who can advise and maybe able to carry out a pregnancy test if you aren't able to - but also for the symptoms you have had too.
    If you would like to discuss in more detail please feel to contact us here at Tommy's Pregnancy Line on 08000147800 or via email midwife@tommys.org

  • By Anonymous (not verified) on 21 Apr 2017 - 20:03

    I took pregnant test 20th april and found im pregnant..my last period was 15thmarch..how many weeks my pregnancy is?..Also im very stressing because i have problem with sciatic pain/low back pain..is this will be the risk to my pregnancy?..
    Thanks.

  • By Midwife @Tommys on 24 Apr 2017 - 09:49


    Hi, Congratulations on your pregnancy and also for finding our site which will help you over the next months.
    If the first day of your last period (your LMP) was on 15/03/2107 then you would around 5+5 weeks pregnant - depending on how long your cycle is.
    If you haven't already please start taking folic acid and vitamin d supplements and visit your GP for a check and to be referred for antenatal care.
    I'm sorry to hear you have sciatic/back pain - neither are a risk to your pregnancy but you may find that you may find the discomfort increasing - again visit your GP early for advice and support.
    Good luck for the coming months!

  • By Anonymous (not verified) on 20 Apr 2017 - 08:37

    Hey there :) i found out that i am pregnant obly yesterday and i am super exited for it. But today i am starting to have a bit of cramps and i am very scared about it i am nearly 7 weeks in (6 weeks 6 days).... i am so scared that i will loose my baby .. is it normal to have cramps or a little bit of pain?

  • By Midwife @Tommys on 20 Apr 2017 - 09:56

    Hi, Congratulations on your pregnancy and also for finding our site which will help you over the next months. It isn't uncommon to experience some mild period like pain which is usually attributed to implantation, or occasional sharp pain where the ligaments are stretching. If the symptoms don't resolve or if they get any worse please see your GP for advice.

  • By Anonymous (not verified) on 16 Apr 2017 - 16:00

    Hi Good eve,
    I am 11 weeks now and no heart beat found when scanned. What should be done to bring the heart beat. I am so scared and under medication to induce heart beat. Till he many weeks I should wait and what is the maximum week ?

  • By Midwife @Tommys on 18 Apr 2017 - 09:51

    Hi there - I'm sorry to hear you have been told that there is difficulty in finding baby's heart activity during an early pregnancy scan. In order to advise I would need some more information and clarification of a few details - please contact us either via email midwife@tommys.org or on our Pregnancy Helpline 08000147800 so that we an offer confidential support and advice.

  • By Anonymous (not verified) on 10 Apr 2017 - 10:53

    Hi ! I am Pregnant and almost 8 weeks. Had issues with my partner because he said he isn't ready financially. I cried and stressed a lot during my 3-4 weeks period, could this have affected the baby in anyway?

  • By Midwife @Tommys on 10 Apr 2017 - 11:01

    Hi there. Congratulations on your pregnancy. And I am sorry to hear that you have had a difficult time with your partner recently too.
    Stress in pregnancy is very tough to deal with, but will not physically harm your baby's growth or well-being. I hope that you partner is being more supportive now and that you have a good friend and family support network too. Please do speak to your GP and Midwife about any ongoing anxiety during your pregnancy as they will be able to support you with more appointments as well as referrals for additional support should you want or need it. Asking for help is always a good thing to do if you are worried or concerned during pregnancy. Do also feel free to call us on our pregnancyline or email us privately on info@tommys.org. We are not counselors, but midwives with a friendly ear, regardless of the situation. Please take good care of yourself.

  • By Anonymous (not verified) on 8 Apr 2017 - 23:48

    Had intercourse with hubby on 26th january.i didn't see my period again till February ending and it has bin regular.could I really be pregnant because I think I am supposed to see the period before February ending.i have not really had any prenancy symptons..just confused...could I be pregnant?

  • By Midwife @Tommys on 10 Apr 2017 - 09:35

    Hi there. It is a little difficult to know. Have you done a pregnancy test at all?
    If you are not pregnant, then it would be sensible to go to your GP to get a referral to a gynae clinic to be reviewed. Sometimes, alterations on your menstrualy cycle pattern can be triggered by something else and so it is best to get it checked out if this is the case. Take good care of yourself

  • By Anonymous (not verified) on 7 Apr 2017 - 15:32

    hi just dnt know wats going wit me ddnt see my periods for 3 months but testing neg I dd 4 test already n I have abdominal pains n sore breast, when I visited a clinic the nurse said I have infection then gave me some treatment but still no change could I be pregnant?

  • By Midwife @Tommys on 7 Apr 2017 - 15:47

    Hi, I would suggest if your symptoms are continuing and you have completed the course of treatment prescribed to you then you need to return to your GP to be reviewed and further investigations. It is very unlikely that you are pregnant if you have continued to have negative pregnant tests however it can be possible but it is important to make sure the infection is addressed too.

  • By Anonymous (not verified) on 6 Apr 2017 - 22:31

    Hi dear, My name is Mary I feel pregnant yet testing negative. I had bleeding for 2 days starting 22/3/2017 and took the final test on 28/04/2017 but came out neg. But till the current moment have not testex

  • By Midwife @Tommys on 7 Apr 2017 - 13:18

    Hi Mary, if you think you maybe pregnant it is a good idea to repeat a pregnancy test as the last one may have been a bit early and no sensitive enough to pick up on a possible pregnancy. I am not sure what symptoms you are experiencing or how you feel pregnant but if that continues with a negative test then you can see your GP who can review the symptoms.

  • By Anonymous (not verified) on 26 Mar 2017 - 12:53

    good day, I have been having normal signs of pregnancy and my mid wife keeps giving me lots of medicines as if I'm too sick.
    I'm scared that the medicine might affect my baby cos it's too much.
    I'm about seven weeks pregnant.

  • By Midwife @Tommys on 27 Mar 2017 - 09:45

    Hi Esyluv,
    Your midwife would only suggest certain medication that is safe for you to take in pregnancy if you really needed it. Also, midwives do not give out medication, unless it has been prescribed by an Obstetric doctor first. Feel free to contact us via email or telephone (info@tommys.org or 0800 0147800) to speak to a midwife in a more private way.

  • By Anonymous (not verified) on 13 Mar 2017 - 15:57

    HEY THERE, MY friend Says she missed her 2nd depo shot on 13th Feb and on 24th Feb she had unprotected sex,so she scared she might be pregnant is the any chance of her to be pregnant?????

  • By Midwife @Tommys on 13 Mar 2017 - 16:36

    It is really important when using Depo-Provera injections as a form of contraception that the injections are given on time. If it is overdue there is a possibility of a pregnancy . There is good information available on the sexual health charity website. http://www.fpa.org.uk/contraception-help/contraceptive-injections . Hope this helps

  • By Anonymous (not verified) on 9 Mar 2017 - 09:16

    I've been on the nur isterate injection for 6 months. I stopped it now 2 months. I've been getting symptoms of pregnancy like very sore breasts nausea no vomiting and stomach cramps.. My last period was on the 13th of Feb... I tested 2 days back and got a negative result was it to early to test
    Could I be pregnant?

  • By Midwife @Tommys on 9 Mar 2017 - 10:08

    Hi, Yes, it is too early to confirm a pregnancy if your last menstrual period was 13/2/17. If you are wanting to become pregnant don't forget to look at our link for preconception care. https://www.tommys.org/pregnancy-information/getting-pregnant/are-you-ready-conceive
    BW Tommy's midwives

  • By Anonymous (not verified) on 8 Mar 2017 - 16:23

    Hi, I am around 6 weeks pregnant and I occasionally get light craping pains in my lower back and around my hips, is this normal? I have no bleeding. This is my second pregnancy but the 1st was 8 years ago and it's difficult to remember.

    Another question - we have guinea pigs kept indoors, do these pose a threat to an unborn baby?

    Thanks

  • By Midwife @Tommys on 9 Mar 2017 - 09:53

    Hi, Mild cramping pains are not unusual in pregnancy. Each woman and each pregnancy is different. It is reassuring that you have no bleeding. Try gentle exercising and keep yourself moving.
    There is no reason to be concerned about guinea pigs although it would be good practice to wear gloves when cleaning them out and also to ensure excellent hand hygiene after handling them. Our link on toxoplasmosis explains why cats are thought to be the animals that transmit this infection in their faeces. https://www.tommys.org/pregnancy-information/i%E2%80%99m-pregnant/antenatal-care/infections-avoid-pregnancy/toxoplasmosis-pregnancy
    Hope this helps. Tommy's midwives

  • By Anonymous (not verified) on 8 Mar 2017 - 10:45

    Hi, i have been off my birthcontrol two weeks ago and me and the hubby had grown up games a day before i stopped taking my tablets, last week i had no bad feelings or symptoms at all but this week i feel rough as hell, i have had headaches been more moody been over sexual (tmi) had felt sick yesterday morning (not had that today). i would just like to know if i should buy a test or leave it down to my bc, i have read that some women it could take months/years to conceive and others within the month of coming off them, please help me someone lol.

  • By Midwife @Tommys on 8 Mar 2017 - 14:48

    Hi Jess,
    I wonder if the symptoms you are experiencing are side effects of coming off the pill.
    Certainly a peak in interest in sex is really common after coming off the pill as in your natural cycle there is a surge in testosterone. (Women talk about having a lower sex drive on the pill).
    You could also be more moody after stopping it. Some women also report headaches, breast tenderness and nausea.
    After stopping the pill you can technically ovulate within a week and sperm can live in a woman's body for 5 days so if you weren't using an alternative form of contraception you could be pregnant. My advice would be to buy a pregnancy test and test when it is 3 and a half weeks since you had sex when coming off the pill. Your periods may take a little while to regulate (1-3 months approximately) so even more reason to have an alternative form of contraception if you aren't quite ready to start trying for a baby.
    I hope this helps.
    Tommy's Midwives

  • By Anonymous (not verified) on 7 Mar 2017 - 13:28

    Hi, I'm 8 weeks & 2 days pregnant although I don't feel pregnant! Is this normal?

    I'm also sleeping for around 16 + hours at a time over the last few days, whereas I was only getting about 2 hours sleep in the weeks prior. Is 16 + hours of sleep & lack of energy normal at this early stage?

    Thank you

  • By Midwife @Tommys on 7 Mar 2017 - 14:38

    Hi,
    Congratulations on your pregnancy! This early stage can be very tiring and every pregnant woman experiences different symptoms which can vary hugely and some never really get any noticeable symptoms. Sleeping a lot more can be normal and part of early pregnancy, however it can also be a sign of low iron levels and sometimes a thyroid problem, if this has been continuing then I would recommend you contacting your GP or midwife. If you have had your booking appointment then they should have taking some blood tests from you, if you chase these up this will tell you your iron levels. If you have not yet had your booking then hopefully this will be soon. If you have any breathlessness or pain then I would advise for you to see your GP as soon as possible. I hope this helps, Tommy's midwives.

  • By Anonymous (not verified) on 15 Mar 2017 - 16:33

    Hi, Thank you for your above response.

    I've been for my booking appointment today & have left feeling totally confused......I had both an external & internal scan & they've said that I'm only 4 weeks pregnant (too early for the booking appointment checks) although checking when I tested posititve, it was 8 weeks ago.

    How is this possible - is something wrong?

    Thanks again for your help

  • By Midwife @Tommys on 16 Mar 2017 - 09:57

    Hi, I think i just replied to you on another page.
    You need to work out the date of the first day of your last menstrual period, and your average cycle length using our pregnancy calculator to estimate your gestation and current due date.
    Once you know this, please go back to your GP to discuss the results and get another date for booking and ultrasound scan. Sometimes dating pregnancies can be confusing, but it is important to know roughly how pregnant you are so that you receive the right care in a timely manner. Take care of yourself

  • By Midwife @Tommys on 1 Mar 2017 - 14:29

    Hi, thank you for your post. It sounds like the bleeding was a really frightening experience. I understand from your message that you went on to have an early scan and you were told that 'there was a pregnancy but it was not really formed' It is such a shock when you experience unexpected bleeding and then end up being scanned. In times of intense stress we don't retain information as we are in shock. Is there a plan for you to return to the hospital for another scan? In some instances it may be too early to detect a heartbeat and confirm a viable pregnancy so returning to be rescanned in 10-14 days can give more information as the developing embryo would be visible as would a heartbeat.
    I hope that this has been scheduled for you? You might like to look at this website for more information.
    http://www.aepu.org.uk/
    Please keep in contact and if you would like to talk to a midwife please contact us on 0800 0147 800 weekdays 9-5 pm
    Tommy's Midwives

  • By Anonymous (not verified) on 1 Mar 2017 - 13:23

    Good afternoon, I really cannot remember my last date for menstrual period, but I tested positive for home test on the 21st.of February. My last period was around the second to the last week in January, and I ovulate d around 4_7 of February. How old can it be?

  • By Midwife @Tommys on 3 Mar 2017 - 12:39

    If you have a positive pregnancy test I would suggest that you arrange to see your doctor. Without accurate dates the best way to date the pregnancy is to do an early pregnancy scan. Your GP will be able to arrange this for you. Best wishes from Tommy's midwives.

  • By Anonymous (not verified) on 28 Feb 2017 - 21:55

    Hi.. I found out i was pregnant a week ago 20th feb 2017.... Just two days ago, i saw blood whilst taking a shower. I rushed to the hsp and was giving injection to stop the blood. It has stopped now but the gyn after doing the ultrasound said there was a pregnancy but not really formed. I'm soo scared and dont know what to do

  • By Anonymous (not verified) on 28 Feb 2017 - 11:25

    I am 11weeks pregnant I seen my baby heartbeat but sometimes I feel like I am pregnant and at times I don't I have back pain and stomach pain where I can't sleep
    The doctor said I have a cyst over my ovaries

  • 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. https://www.tommys.org/pregnancy-information/im-pregnant/early-days-pregnancy/morning-sickness

    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

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