First trimester: weeks 1 to 12

You're pregnant: congratulations! The first weeks of your pregnancy are a vital time as your body gets 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!

When am I due?

Find out your due date using our due date calculator!

When will I see a midwife?

Your first midwife appointment (also known as antenatal appointment) is the 'booking' appointment. This usually happens between week 8 and 10 of your pregnancy. Find out how to register with a midwife and when your appointments will be here.

Keeping your baby safe

There are some things that you can do during pregnancy that have an effect on your baby. Find out about them by clicking the link below.

Find the complete list of pregnancy dos and don'ts (and reasons why) here

Not sure whether you are pregnant?

Find out about the symptoms that mean you may be pregnant here.

Your physical and mental health in pregnancy

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. 

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. 

Exercise, such as yoga, has been shown to reduce anxiety and is a great way to stay active during your pregnancy, too.

Read more about mental wellbeing in pregnancy

Read more about diabetes and pregnancy

Read more about pregnancy with a high BMI

Read more about exercise and pregnancy

Read about the symptoms to look out for in pregnancy

Track your baby's development

Sign up to a free pregnancy email from our midwives to track your baby's development and give you reminders of all you need to know through the nine months of pregnancy. Click here to sign up.


Follow Tommy's PregnancyHub on Instagram

Find out more about the first trimester


NHS Choices. Your pregnancy week by week (Page last reviewed: 28/02/2017 Next review due: 28/02/2020)

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

NICE (2008) Antenatal care for uncomplicated pregnancies, NICE Clinical Guidelines 62. National Institute for Health and Care Excellence

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    Last reviewed on June 28th, 2018. Next review date June 28th, 2021.

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    Please note that these comments are monitored but not answered by Tommy’s. Please call your GP or maternity unit if you have concerns about your health or your baby’s health.
    • 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 LoLo (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 maureen (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 Lilian (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 Fredy (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 Salewa (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 Isabella (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 [email protected] with your query so we can help answer your questions.

    • By Maria (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 [email protected]

    • By Elaine (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 divya (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 queenspa (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:

    • By Anonymous (not verified) on 29 Dec 2016 - 13:36

      Hi, I had my last period on 25th of Nov. Today I've got a positive results in my home pregnancy test. But last week I have had severe chickenpox. Will it affect my baby?

    • By Midwife @Tommys on 5 Jan 2017 - 15:46

      Thank you for your question. There is a known small risk to the baby if a mother has chicken pox in early pregnancy and I recommend that you request a referral to your maternity unit fetal medicine unit (FMU) to discuss this. Your GP will be able to arrange this.

    • By Confused (not verified) on 26 Dec 2016 - 15:26

      Recently in Nov I have gotten my implant removed and a week later I started the nuvaring. I didn't use a condom with my boyfriend for the first seven days either or anytime after that and he didn't pull out. On my ring-free week I spotted and my menstrual has never came on. Through this whole month of dec I have been having bad insomnia sometimes I can't sleep at all and other times I am in and out of sleep. I tried drinking some alcohol and my stomach started hurting so I stopped and I can't lay on my stomach either it's uncomfortable. So could I possibly be pregnant? Because before this I could sleep my day away and I'm not stressing or worrying about anything please give me some type of clarity to this?

    • By Midwife @Tommys on 5 Jan 2017 - 16:59

      It may be possible that you could be pregnant, if you have not done so already I would suggest to take a pregnancy test. It could be that a change in contraception has disrupted your cycle however it is important to found out whether you are pregnant or not first. If you are feeling anxious or would like to talk further then please email us [email protected] and we will try to support you best we can

    • By Midwife @Tommys on 21 Dec 2016 - 15:59

      Hello thank you for posting. I'm sorry that you are feeling so anxious about whether your pregnancy will be successful or end in miscarriage. It is a very common way to feel in the early days of pregnancy, which last a lifetime when you are waiting for reassuring milestones, like a scan and then baby movement months later.
      Women often feel quite lonely too as they may not wish to share their news until they have had confirmation that the pregnancy is progressing normally.
      Pregnancy is a time of great change in both the mind and body bringing up all kinds of new emotions, thoughts and feelings, most of these due to your pregnancy hormones.
      Is there a good friend or close relative that you can talk to? You mention that you have suffered from anxiety in the past and if this becomes overwhelming getting some counselling early on may be an option for additional support. You can self refer or make an appointment with you GP.
      You will also be meeting with your Midwife for your first appointment known as the booking appointment early in the new year. Please let your midwife know how you've been feeling so that your team are aware and can offer help.
      There are a few links on our website below:
      You might also consider finding a local yoga class run specifically for pregnancy to meet some new friends who live nearby. Most importantly please don't suffer in silence there is support out there and you are not alone in how you are feeling.
      Tommy's PregnancyLine will be open tomorrow and then reopens on 4/1/2017 so give us a call too on 0800 0147 800
      We hope to hear from you
      Tommy's Midwives

    • By Helen (not verified) on 20 Dec 2016 - 20:32

      Hello, I'm currently 4 weeks 4 days. Very early days. I'm struggling with anxiety about whether or not the pregnancy will be successful. There's nothing to say it won't be, I just struggle with anxiety at times. Do you have any advice about how to get through these early weeks/days?

      Thank you.

    • By Midwife @Tommys on 30 Nov 2016 - 09:55

      Hi, I'm sorry that you are waiting for your period to return and so far, after 7 months it hasn't.
      There is no evidence that Depo-Provera has any long term effects on a woman's fertility but it can take 3 to 12 months for your periods to return to normal.
      You have done the right thing by going to see your GP and being on the waiting list for a referral to a gynaecologist is the next step.
      I'm afraid this isn't an area that midwives specialise in but you have been to your GP and have a referral so unfortunately it is a matter of waiting now for your cycle to return or the appointment with the specialist... whichever comes first. Best of luck.
      Tommy's Midwives

    • By Anonymous (not verified) on 29 Nov 2016 - 15:12

      I have been on the depo for about a year, I have stopped it since the past 7 months and to date I have not got my menstuation. I've been to a GP twice, at my first visit he prescribed Provera 5mg which I had taken for 10 days. After I taken it I constantly had severe tummy cramps n body pains, I had visited him the 2nd time n he suggested I wait for another 3 months for my menstual cycle to return after the depo n today marks 3 months since I been to him n no menstruation. I have picked up a lot of weight n I'm very concerned about this issue. He has now reffered me to see a gynae, I am on a waiting list for a visit. Until then would you please advise me on my situation and wat could be the cause of my menstrual cycle been delayed. Thanks in advance for a reply

    • By amy (not verified) on 11 Dec 2016 - 21:00

      I had my son in October 2013 and had the depo straight after he was born continually.

      November2015 I stopped the depo I got my first period in August 2016 then every 30days I found out a week ago I'm now pregnant. Don't give up, your body will kick in soon . I was desperately googling when periods return after depo and there really isn't that much information out there, but it will happen keep positive xxx

    • By Midwife @Tommys on 12 Dec 2016 - 09:22

      Hi Amy. Thank you for your support of Tommy's and for kindly sharing your story!

    • By Wilmai (not verified) on 22 Nov 2016 - 20:56

      Can you give your advice about travelling druing pregnant. At around 9-11 weeks?
      Your reply is highly apreciated.
      God bless

    • By Midwife @Tommys on 23 Nov 2016 - 12:46

      Hi Wilmai,

      Please feel reassured that it is fine to travel in pregnancy.
      Flying in pregnancy is not unsafe. It does not cause miscarriage for a low risk, healthy pregnancy.

      If you plan any other trips abroad in this pregnancy airlines tend to want a letter to say you are fit to travel when you are 28 weeks or over, but even at 24 weeks, it may be worth discussing this with your midwife or GP to say that you fit to fly and you would have to have no complications.

      You may also need to check with your insurance company to see if they cover you in the event of anything happening while you are away and will they cover medical care. You also need to check that there is sufficient health care available at your destination, just as a precaution.

      The main complication with flying when pregnant is the increased risk of deep vein thrombosis (DVT) but there are precautions you could take, like walking around during the flight and drinking plenty of fluids. Most people choose to fly in their 2nd trimester as they are over the initial worrying 12 weeks and they are not close to delivery. Obviously travelling nearer to the end of pregnancy carries the risk of going into premature labour, this is relatively uncommon but we cannot always say who this may happen to and when.

      It would also be worth to note the heat and humid conditions and to be extra careful with drinking and eating when abroad. Many women do go on holiday in pregnancy as it is nice to have some time away together before baby comes along. I hope this has helped and you enjoy your holiday!
      Tommy's Midwives

    • By Sristy (not verified) on 19 Nov 2016 - 07:45

      My last period was on 17th oct and this month i missed my period ,i test it in home but the result is negetive i m in worry am i pregnent or not please reply

    • By Midwife @Tommys on 21 Nov 2016 - 08:50

      Hi, it might be useful to repeat the test again. If you are still unsure and have still not started your period, it might be a good idea to book an appointment with your GP. If the GP is concerned , you may be referred on for some gynae investigations.

    • By farah (not verified) on 11 Dec 2016 - 10:47

      Same thing happened to me last month and when I tested that time it was negative but after two weeks I tested again and this time it was positive and now im 7 weeks pregnant. Best of luck to u.

    • By feedback (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 [email protected] so we have your email address to be able to update you.

    • By xty (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 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.

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