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.


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 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

    • By Lilian 18 (not verified) on 24 Nov 2018 - 03:33

      Hi. I'm 5 weeks pregnant. But my beta hcg is low 63. Is there something wrong with my pregnancy? Thank u.

    • By Midwife @Tommys on 26 Nov 2018 - 11:35

      Hi Lilian, This is still within the very wide range for this stage of pregnancy. Are you having a repeat blood test? If so the levels should rise steeply over the next few days and weeks.

    • By Michelle (not verified) on 28 Nov 2018 - 15:21

      I was told my hcg levels was low when I went into the ER for not feeling well just to find out I was pregnant, I have irregular periods but they only last 3 days and Last menstrual was around October 23 or 24th maybe 25. Not quite sure but it would always be gone around the 26-27th. And today is November 28,2018 & I don't have & appointment until December 12,2018 is it normal to have my hcg low around this time? They wanted to do & ultrasound but they couldn't because it was just me and my toddler there with no other adult to maintain my baby as they proceed. So I had to sign out, the 12th seems kind of far to me, because I want everything to be okay. But just being patient & praying but just curious to know is this early normal and how far along can I possibly be.

    • By Midwife @Tommys on 29 Nov 2018 - 13:39

      Hi Michelle, Thank you for your comment. I am sorry to hear you are having an anxious wait. When you go to your appointment on the 12th they may repeat your blood test to ensure the your Hcg levels have increased rapidly in addition to performing a scan. At this moment in time these would be the only way to confirm how far along in the pregnancy you are.
      I hope all goes well on the 12th for you.
      Best Wishes - Tommy's Midwives

    • By HELP (not verified) on 23 Nov 2018 - 07:34

      My last period was last 11th of November. I have unprotected sex with my husband last 10th of Novemeber. My cycle is usually 26 or 28 and period lasts up to 6 days. Is it possible that i might get pregnant? Thanks

    • By Midwife @Tommys on 23 Nov 2018 - 10:51

      It would be very unlikely to have conceived a pregnancy if you came on your period the next day. A period is a sign that you are not pregnant, and it is normal to ovulate in the middle of the cycle, so this is when pregnancy is most likely.
      Best wishes
      Tommy's midwife

    • By Ag (not verified) on 12 Nov 2018 - 11:13

      Good day, found out I was pregnant two weeks ago. Am still breastfeeding my 1yr plus daughter.. Am finding it difficult to.. He do I wear my daughters ..plz help

    • By Midwife @Tommys on 13 Nov 2018 - 12:26

      Hi - Congratulations on your pregnancy. Yes you can breastfeed whilst pregnant, your body will carry on making milk while you're pregnant, so you'll be able to breastfeed.

      While you're breastfeeding your toddler, your unborn baby will still get all the nutrients she needs from your body. Make sure you're eating well, so you don't go short yourself. Keep taking your daily vitamin D and folic acid supplements.

    • By Brenda (not verified) on 10 Nov 2018 - 17:29

      I think I'm pregnant for the last two months because I experience some pregnancy signs but whenever I test it's negative and even experience some little bleeding can I be pregnant?

    • By Midwife @Tommys on 13 Nov 2018 - 12:24

      Hi - please visit your GP and discuss your symptoms, especially if you feel there has been a change to your regular period.

    • By Fortunate (not verified) on 7 Nov 2018 - 17:32

      I last seen my periods on the 26th of August and I had unprocted sex with my boyfriend till 4 September. so am actually wondering if I concieved that time because after two weeks I had already had pregnancy symptoms and I took a pregnancy test and it came positive.

    • By Midwife @Tommys on 9 Nov 2018 - 15:56

      Hi Fortunate,
      It is possible that you did become pregnant during this time, everyone experiences pregnancy symptoms differently and ovulate at different times, that is why your period dates are used to estimate how many weeks you are until you have your scan.
      Best wishes
      Tommy's midwife

    • By wilma (not verified) on 5 Nov 2018 - 12:09

      I last seen my periods between 25 and 27 September. How many weeks am i?

    • By Midwife @Tommys on 5 Nov 2018 - 16:07

      Hi Wilma
      You would be no more than 6 weeks exactly today if your last period started on the 25th Sept. You should go to your GP to book your first scan and your booking appointment with the midwife. Congratulations. Tommy's Midwife

    • By Mary (not verified) on 2 Nov 2018 - 08:10

      My last period was around 20th/21st September. Had unprotected sex, (but didn’t even ejaculate at all) on 27th September. It’s now 2nd November and I haven’t had my period yet. I’ve got a slight blocked nose, headaches and feeling extremely groggy in the mornings, I feel sick during the day, but I don’t actually vomit or anything, breasts feel sensitive and tender and been needing to go toilet, more Than Normal. I haven’t had a pregnancy test, because I’m just hoping it’s PMS but my period has been consistent every month!

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