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 Kerri (not verified) on 17 May 2019 - 08:45

      I missed my period for 7 days. I did a urine test and it said that I am 2-3 weeks pregnant. I then did a blood test which confirmed that I am pregnant with a HCG count of 169. The day after my blood test, I started my period. The doctor advised I must do blood tests again in 4 days time to check if my HCG count has increased. 4 days are still so long and its making me anxious. Am I having my last period because its early days or have I had an early miscarriage?

    • By Anonymous (not verified) on 30 May 2019 - 21:52

      I'm having same situation. 7days late and 2 positive pregnancy test . Am I pregnant or should I wait more for my periods to come back?

    • By Anonymous (not verified) on 7 Jun 2019 - 11:06

      If the pregnancy test came back positive they knew most definitely pregnant

    • By Baby (not verified) on 14 May 2019 - 17:59

      hi.... I had some signs of pregnancy during the 2nd week of April.... so I went for a pregnancy test via blood test nd it came out positive.... but on the same day I I got the test for a positive pregnancy result test my mestratution started that lasted for 4days... confused tho.... I started monitoring myself,after the menstrual period... so I found out I sleep too much, feel week very often, eat too much, have sore breast .... now the date of that the last period was 12-15... now in may the am having cramps, light spotting of blood.. am confused... please help

    • By Jas (not verified) on 4 May 2019 - 03:44

      I went to the hospital and they gave me a urine test it showed I was pregnant they then drew blood it was called a titer they checked for my HCG levels and my baby blood type well I was told it's very little fetus growth and my HCG levels was only 100 but they didn't tell me how far along I was and they want me to come back in three days to repeat the titer well I went to the hope center and they told me I was four weeks pregnant but they went off my lmp I had a miscarriage before does that mean that's what this is reason why my levels are only 100 and why the ER couldn't tell me how far along I am only styoms I have is sore breast peeing alot eating alot sleepy and cramps but today only had peeing alot eating alot and little sleepy no cramps

    • By Megan (not verified) on 3 May 2019 - 19:06

      I had started my period april the 4th it lasted 4 Days then i started again on april 29th it only lasted 3 days
      Could i be pregnant i have taken several pregnancy test and they keep showing faint positive lines? I havent been feeling like myself lately

    • By Megan (not verified) on 3 May 2019 - 19:03

      I had started my period april the 4th it lasted 4 Days then i started again on april 29th it only lasted 3 days
      Could i be pregnant i have taken several pregnancy test and they keep showing faint positive lines? I havent been feeling like myself lately

    • By Anxious Mum (not verified) on 1 May 2019 - 23:29

      Hello, I am 40 year old, have had three ( nearly four) failed pregnancies. Had two miscarriages and an ectopic ( with a tube removed). I am 6 weeks 5 days pregnant now, my hcg levels were slow rising with 2900 and 3300 in 48 hours. Scan revealed gestational sac but no yolk sac or embryo, also sac marked as irregular at 7 * 4 * 7, scan was hard and painful as they state visibility was poor due to its position, not sure what that means.
      Can you please advise?

    • By Scared (not verified) on 29 Mar 2019 - 00:03

      I’m having what feels like a period and they look at the baby today and it was fine. Have you heard of this before at 12 weeks?

    • By bria (not verified) on 12 Mar 2019 - 04:34

      this is every helpful. I will keep using this link.

    • By Jessy (not verified) on 10 Mar 2019 - 09:45

      Me and my partner had sex one month back. 1 week after that, I started feeling cramps,giddy and tired,back cramps.i went to doctor and took some prolactin level was 55..Now I got my periods which was not heavy like regular periods, that to for only 2days with out any severe was light bleeding than I pregnant?

    • By Blessing (not verified) on 10 May 2019 - 16:41

      I am not sure but think you are. Women who are pregnant have the prolactin levels btw 34 to 386 ng/mL. You might want to confirm from your doctor.

    • By Maria (not verified) on 18 Feb 2019 - 09:43

      My breast has been hard since the last week of December. My normal mensuration came on the 20/11/2018 but in December and January it as been very light and only two days or less than. I have been having several pregnancy signs could I be pregnant cause I have done home test but it comes out negative

    • By Midwife @Tommys on 21 Feb 2019 - 12:43

      Hi Maria, Thank you for your comment.

      As it has been a couple of months since your last period, it would be advisable for you to see the GP. You are getting negative pregnancy tests but you are still not having periods only spotting. The GP will be able to take some bloods to check your hormone levels and if you need a referral then he can do this. Take Care, Tommy's Midwives x

    • By Lizzy (not verified) on 14 Feb 2019 - 21:43

      I'm four months pregnant but my Tommy is not coming out pls what can I do

    • By Nicola (not verified) on 10 Feb 2019 - 02:09

      Hi I took a clear blue test on Thursday afternoon and it came up pregnant 3+ how far would i be and my boobs were getting really sore in the past week now and my lower back is sore aswell.

    • By Midwife @Tommys on 13 Feb 2019 - 13:12

      Hi Nicola - you can visit our page here to work out roughly how many weeks pregnant you are and when your due date might be -
      All the best, Tommy's Midwife

    • By Casendra (not verified) on 1 Feb 2019 - 16:15

      Hi, my first day of the last period was on 8.12.18 & Jan I haven't got my period... me and my hubby have regular intercouse. I have noticed spotting last week one day and even this week on Friday . I have used the pad but nothing much just a few drops .. Is this due to pregnancy... pls advise

    • By Midwife @Tommys on 13 Feb 2019 - 13:09

      Hi Casendra - you will need to do a pregnancy test if you have not seen your period since 8th Dec until now. If you are not pregnant, then you need to book to see your GP to review why your menstrual cycle has hanged suddenly. All the best, Tommy's Midwife

    • By Ayesha (not verified) on 30 Jan 2019 - 14:47

      Hi, it is common to have a 1 week late for a baby growth? If calculated on my last period, i’m now in 8 weeks pregnancy. But after i did a scan, it shows im 6 week pregnant. Another thing is i dont have any symptoms like nausea or what. But my breast is sore last week.

    • By Midwife @Tommys on 31 Jan 2019 - 11:08

      Hi - thank you for your message. There can be some variation by a few days on how pregnant you are and what it shows up on the scan as. This maybe due to a longer than average cycle or your dates varying a little.

    • By Adelina (not verified) on 22 Jan 2019 - 16:15

      Hello. I did a pregnancy test last night and is show my I am pregnant in 2-3 weeks but after I read more carefully the instructions and they was saying to with the first urine but I didn’t do with the first.
      And my boobs it’s hurting me from more than one week and I feel them bigger!
      The pregnancy test is good?

    • By Midwife @Tommys on 23 Jan 2019 - 16:38

      HI Adelina
      Yes, you are pregnant. the best time to take a pregnancy test for the most accurate result, is with the first wee of the day. But if you took the test later in the day, and it still shows pregnant, then this is right
      Congratulations, all the best! Tommy's Midwife

    • By Rebecca (not verified) on 21 Jan 2019 - 12:03

      I’m taking a pregnancy supplement but before my positive result I was aso taking vit b6 100g to extend luteal phase . Should I keep taking it ? Or cut down slowly . It has been helping with nausea

      Please help- also do I need a b complex

    • By Midwife @Tommys on 25 Jan 2019 - 15:59

      Hi Recbecca,
      Are you able to drop us an email with a little more background information to [email protected] and we will advise you there.
      Tommy's midwife

    • By Nadeesha (not verified) on 11 Jan 2019 - 09:10

      I had two drops of blood pregnancy is 9 weeks and I feel some pains in my lower back is this normal?

    • By Midwife @Tommys on 11 Jan 2019 - 12:35

      Hi Nadeesha,
      I would suggest to put on a pad and monitor for any further blood loss. If this continues or your pain is worsening then do see your GP for a review.
      Best wishes
      Tommy's midwife

    • By Concerned (not verified) on 10 Jan 2019 - 10:32

      Hi my period was 4 days late, and I normally bleed for 7 days but this time I only bled for 2 days and it stopped for 2 days then I had a very light bleed for a day. I had unprotected sex with my partner on 23rd Dec, and I'm now experiencing lower back pain, headaches and constantly tired. Am I pregnant or is my body fooling me because we r trying 4 a baby

    • By Midwife @Tommys on 10 Jan 2019 - 14:57

      Hi - thank you for your message.
      If your period is late and you think you may be pregnant, you should take a pregnancy test to determine if you are pregnant or not. If you are, please see you GP/Dr soon for early pregnancy advice and to be referred to a maternity unit. If you haven't already, please also start taking folic acid supplements.

    • By Diane (not verified) on 31 Dec 2018 - 10:34

      Hello, I'm already 30 and this is my 1st time to miss my period. My last first day of period was Nov 25. Last intercourse with my hubby was Dec 6-7. Today is Dec 31 already and still no menstruation. Is there a possibility that I'm pregnant. No PT done yet.

      Thank u

    • By vicky (not verified) on 30 Dec 2018 - 20:01

      Hi my last period was 26th nov i finnished 29th nov was dry for 3 days then ive had spotting on n off since then is this normal i am pregnant

    • By ann (not verified) on 30 Dec 2018 - 03:09

      hi. just want to say that i had 3 preg kits tested resulting to positive. the 1st day of my last period was on nov. 22. i havent seen my ob yet. can u help me if how many weeks iam now and when is my possible due date. tnx

    • By Kia (not verified) on 24 Dec 2018 - 21:11

      Nov. 12-20 was my last cycle am I pregnant??? I’ve token several home pregnancy tests and it said I wasn’t

    • By Annie (not verified) on 19 Dec 2018 - 12:17

      My last period was October many weeks of pregnant an I?

    • By Midwife @Tommys on 19 Dec 2018 - 15:47

      Hi Annie
      Presuming you have a 28 day cycle and using your LMP as the 20th Oct, you are approx. 8+4 days pregnant.
      Congratulations. Please get in touch with your GP so that you can be referred for midwife and scan referrals. Tommy's Midwife

    • By ??? (not verified) on 16 Dec 2018 - 17:47

      Hi I currently found out I'm pregnant and will be visiting my midwife for the 1st time at 10 weeks pregnant is that normal? And will she send me for my 1st lot of blood tests is that normal at 10 weeks or should the blood tests be done earlier? Xx

    • By Midwife @Tommys on 19 Dec 2018 - 15:44

      Hi there.
      Usually, the first booking apt with the midwife will take place between 8 - 11 weeks of pregnancy. Some midwives take your bloods and others will send you to your local phlebotomy service. Each borough, or even clinic can work differently. But either is fine. You will have your first scan around 12 weeks
      Congratulations and all the best. Tommy's Midwife

    • By Rama (not verified) on 16 Dec 2018 - 09:38

      Hi, my last period was oct 19 2018. I visited doctor when I was 6th week pregnant. Doctor did vaginal scan and she said my pregnancy may lead complications because pregnancy planted on right horn of uterus and I may have bicornuate uterus(she s not sue).. now I am running 9th week if I am not wrong. But my doctor statement made me thinking too much about negative aspects. Actually I am fine with normal pregnancy features like nausea, sore breast, tired, vomiting sensation and all. Please suggest me.. I am totally confused.

    • By Midwife @Tommys on 19 Dec 2018 - 15:40

      Hi Rama
      You should go back to see your doctor again to ask whether you need any extra scans or appointments in relation to this. You sound as if you need more information, directly relating to you and your medical history, and your doctor or midwife can provide these.
      All the best - Tommy's Midwife

    • By Kelly (not verified) on 13 Dec 2018 - 16:53

      I am around 8 weeks. When I first found out at around 5 weeks I had terrible nausea, sore breasts, and I was sleeping more than I was awake. I have read that this typically eases by 12 weeks. However, I have had a previous miscarriage so for that reason I meticulously monitor my symptoms as they disappeared last time just beforehand. I have noticed that my nausea has stopped already, my breasts don't feel as sore as they did initially, and although I am still tired this does seem to have improved. I am worried that this reduction in my symptoms at this stage means I am heading for another miscarriage. Is it normal to only experience symtpoms for a few weeks and to improve this early? My husband laughs because I've got into a habit of checking my boobs every half hour to make sure they are still a bit sore!

    • By Midwife @Tommys on 14 Dec 2018 - 15:53

      Hi Kelly,
      It can be really normal for symptoms to vary and come and go, but it is completely understandable that you are worried given your past experience of a miscarriage. It can be normal for symptoms to start to reduce at this stage, however if you have noticed a sudden loss of symptoms or are worried then do speak with your GP.
      Best wishes
      Tommy's midwife

    • By Alex (not verified) on 12 Dec 2018 - 06:26

      Does Implantation cause a light like period for a few days or a few drops of blood? I had a few drops as well as cramping, really sore boobs and very oily hair? Not sure what that’s about.

    • By Midwife @Tommys on 13 Dec 2018 - 16:01

      Hi Alex, Thank you for your comment.

      Some women can have a little spotting around the time of implantation and some have nothing at all. It is very difficult to establish how and when implantation occurs so we would suggest that you wait and see if you miss a period and then take a pregnancy test to see if you are pregnant. Take Care, Tommy's Midwives x

    • By Kerri (not verified) on 17 May 2019 - 08:38

      I was 7 days late of getting my period. Tool a test and it said im 2-3 weeks pregnant. I then went to do blood tests to confirm and it did, HCG 169. The day after the blood tests, I started my period. The doctor said I must do blood tests again in 4 days to see if my HCG count has increased. 4 days feels so long though. Is it normal to get my period so early in the pregnancy? Or what could be happening?

    • By Roxy (not verified) on 11 Dec 2018 - 13:28

      Hi, I had my period on the 19th November for 5 days. I then had spotting on the 9th December so on the 10th December I decided to do a pregnancy test. It was positive. I also did a clear blue pregnancy test which was positive and said im 3+. Im confused as I was only on my period on the 19th November so how am I pregnant and how can I be 3 weeks. Is it possible that all 3 positives were false?? please help

    • By Midwife @Tommys on 13 Dec 2018 - 15:34

      Hi Thank you for your comment.

      It is highly unlikely that all 3 tests were a false positive. If the first day of your last period was the 19th November then this would put you around 3-4 weeks today, so your dates do add up. If you are unsure of your dates then your GP can always refer you for an early dating scan that will tell you what gestation you are at in your pregnancy. Hope this helps, Take Care, Tommy's Midwives x

    • By P (not verified) on 11 Dec 2018 - 09:54

      Hi, the first day of my last period was 12/10/18, calculating me at 8 weeks pregnant, but had early scan and they said size is 6 weeks. I’m going back for another scan on Friday to check as may have stopped growing, but is it possible for it to be the size from actual conception which would be six weeks? Or is it always from the first day of last period? Thank you

    • By Midwife @Tommys on 13 Dec 2018 - 15:26

      Hi P, Thank you for your comment.

      We always take the dates from the first day of your last period so this would put you at around 8 weeks. Having another scan will give you a better idea of how your pregnancy if progressing. Take care, Tommy's Midwives x

    • By Rebecca (not verified) on 29 Nov 2018 - 19:42

      My last day of my last period was 10/26/18. How many weeks pregnant am I?


    • By Midwife @Tommys on 30 Nov 2018 - 10:45

      Hi Rebecca,
      If you have a regular 28 day cycle then you are about 5 weeks pregnant, however when you have your scan at about 12 weeks this will give you your estimated due date and therefore your gestation more precisely.
      Best wishes
      Tommy' s midwife

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