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 Midwife @Tommys on 21 Jun 2018 - 12:05

      Hi Glaiza, Thank you for your comment and congratulations on your pregnancy.
      If your last period was on the 14th April then this would give you an estimated due date of around the 17th January 2019. Hope this helps, take care, Tommy's Midwives x

    • By Keri (not verified) on 16 Jun 2018 - 23:56

      Hello, I am 12 weeks + 2 days by my LMP. This was a unplanned pregnancy and now I feel guilty as I have a BMI of 42. The booking appointment midwife was not very helpful as she said I would not see her again. My scan is booked and I have read online that they may opt to do a internal scan instead of a abdominal. Is this the most likely outcome?

    • By Midwife @Tommys on 21 Jun 2018 - 11:58

      Hi Keri, Thank you for your comment and congratulations on your pregnancy.

      Please try not to feel guilty, this pregnancy wasn't planned but it is important that you use this time to try and make the right dietary choices and maintain a healthy pregnancy, which I am sure your midwife has spoken to you about. With regards to your scan, because baby is still small at this stage, an abdominal scan may be difficult to do so in order for the sonographer to get a good view of baby, an internal scan may be needed. Women also have internal scans in early pregnancy as the baby can be so small to see on an abdominal scan. When you go for your scan the sonographer should try with an abdominal scan first and if it is only necessary they will suggest an internal scan. If you are concerned then please speak to the sonographer before your scan who will be able to reassure you. Hope this helps, Take Care, Tommy's Midwives x

    • By Pearl (not verified) on 15 Jun 2018 - 10:25

      Hi i just found out on the 6th of may i'm 8weeks pregnant, so i just want to now when will the baby be deliivered.

    • By Midwife @Tommys on 15 Jun 2018 - 14:02

      Hi Pearl,
      According to the dates that you have given, your baby will be due about 17th December, however when you have your dating scan at about 12 weeks this will give you your most accurate due date and this will be used throughout the rest of your pregnancy. It is normal for a baby to be born any time between 37-42 weeks of pregnancy, so in your case 26th Nov-1st January.
      Best wishes
      Tommy's midwife

    • By Morgan Bishop (not verified) on 14 Jun 2018 - 20:35

      I just had a doctor appointment and my pregnancy test is positive. My lmp was May 13th thru 16th.
      How are along am I?

    • By Midwife @Tommys on 15 Jun 2018 - 14:05

      Hi Morgan,
      According to your period dates, you will be due about 18th Feb and so you are about 4 weeks and 5 days pregnant.
      When you have your dating scan at about 12 weeks this will give you your most accurate due date which will be used for the rest of your pregnancy.
      Best wishes
      Tommy's midwife

    • By Kate (not verified) on 14 Jun 2018 - 19:49

      Hello my name is Kate, I had unprotected sex in February, I had sex 7-8 times, my recent boyfriend I was with we had sex may 11th, I was suppose to have my period may 14th, but it’s started the 15th, I had my period and June 13th I was suppose to start again and I haven’t, therefore I am two days late can someone please tell me whether I’m pregnant from may or February because I am getting fatter but I have had period since feb, I am 16 I have no clue what to do, I can’t talk to my mother because well she never listens to me, I bough six tests in March and they all came back negative but now I’m late 2 days and scared out of my mind please help me

    • By Midwife @Tommys on 15 Jun 2018 - 14:09

      Dear Kate,
      I am sorry to hear that you are so scared, please know we are here to support you best we can. From the dates that you have provided, you say that you have had a period on the 15th May therefore you would have gotten pregnant after this time. Have you had a positive pregnancy test? I think it may be easier for you to either email us [email protected] or call us 0800 0147 800 as I am a little unclear on your dates so we can talk further in a confidential way.
      Best wishes
      Tommy's midwife

    • By Sudha (not verified) on 14 Jun 2018 - 09:09

      Hi, my lmp was 10th may 2018, I done my home pregnancy test result on 12 th June and I got mild line in the test region, which means positive or negative? If positive when can I go to doctors check up? I don't have any pregnancy symptoms

    • By Midwife @Tommys on 15 Jun 2018 - 14:25

      Hi Sudha,
      Any line we would take as a positive, even if it is faint so this means that you are pregnant. We would advice for you to contact your GP so they can refer you to maternity services for your antenatal care.
      Best wishes
      Tommy's midwife

    • By Pearl (not verified) on 14 Jun 2018 - 06:24

      The first date of my LMP was April 8 , how many weeks am I ? And when will this feeling (mouth tasting somehow , feeling irritated with smell , always looking for chewing gum or sweet to ease d taste of my mouth) be over?

    • By Midwife @Tommys on 15 Jun 2018 - 14:28

      Hi Pearl,
      Given your period dates you are about 9 weeks and 5 days pregnant. It is difficult to say when this symptom will be over, for some it can last all pregnancy and others it will disappear during the first trimester. Hopefully you have booked with a midwife by now and they have arranged your scan for you to date your pregnancy accurately, if not then do see your GP.
      Best wishes
      Tommy's midwife

    • By Kirsty (not verified) on 13 Jun 2018 - 20:29

      Hi there, my last period date was 25th March. How many weeks am I pregnant and when would I be due? I’m first scan is in 2 weeks time

    • By Midwife @Tommys on 15 Jun 2018 - 14:31

      Hi Kirsty,
      According to your dates you are due about the 31st December making you about 11 weeks and 4 days pregnant currently, however your scan in two weeks will give you your official due date which will be used throughout the rest of your pregnancy.
      Best wishes
      Tommy's midwife

    • By joy (not verified) on 13 Jun 2018 - 10:06

      my lmp was 06/05/2018. and I am pregnant. I am how many weeks pregnant and when is my due date?

    • By Midwife @Tommys on 13 Jun 2018 - 11:59

      Hi Joy
      Using your LMP of 6/5/18 and presuming you have a 28 day cycle. The most pregnant you are is 5 weeks. Your due date would be around 11th Feb 2019
      All the best
      Sophie,Tommy's Midwife

    • By emma (not verified) on 13 Jun 2018 - 09:40

      i had my last period on the 16th may 2o18 and i had intercourse on the 24th may. i have been getting signs. waves of nausea.. gassy reflux.. constipation.. twinges in the lower ab and back.. also i got streps throat the other day out of nowhere.. was the 10th june to early to take a test.. how far along would i be? please help with advice x

    • By Midwife @Tommys on 13 Jun 2018 - 12:38

      Hi Emma
      the best time to do a pregnancy test, is with the first wee of the morning and to wait at least a week after your period is late. In this time, the HCG levels (pregnancy hormones) will have had time to build up in your system. Testing before your period would be due can give a false negative result. So wait until a week after your period is due and test again. Then, the result will be a accurate whether it is negative or positive.
      If you have not seen your period after 1 week, and you have a negative test, please to go to be seen by your GP.
      All the best
      Sophie,Tommy's Midwife

    • By Melissa (not verified) on 13 Jun 2018 - 03:27

      I'm 12 weeks I have fibroids & the pain gets bad at times what can I do to ease the pain

    • By Midwife @Tommys on 13 Jun 2018 - 12:41

      Hi Melissa
      You need to be seen by your Obstetric consultant at the hospital as soon as possible. They will be able to support you and guide you in what to expect with a pregnancy with fibroids.
      All the best
      Sophie,Tommy's Midwife

    • By Bex (not verified) on 11 Jun 2018 - 17:47

      Hi, just looking for advice, I had the implant up until February this year, and had regular periods up until this month I was due on today (11th) but nothing, so I've taken a test and it's negative. What's the best thing to do next? Do I test again tomorrow first thing in the morning or wait a week?
      Thank you. X

    • By Midwife @Tommys on 12 Jun 2018 - 14:27

      Hi Bex,
      Just so that I'm clear, since your implant was removed in February your periods returned to a regular cycle and you should have started your period on the 11th?
      I would repeat the pregnancy test this week if your period doesn't come first. The hormone hCG that the test is sensitive to usually doubles every 48 hours so it would be wise to wait to allow this to happen and also not to spend money on expensive repeat tests.
      Take care and please get back in touch if we can help you
      Anna-Tommy's Midwife

    • By Bex (not verified) on 12 Jun 2018 - 15:16

      Yes, I've had regular periods since having the implant removed.
      Thank you x

    • By grace (not verified) on 11 Jun 2018 - 07:10

      my lmp was 23rd of march 2018

    • By Midwife @Tommys on 11 Jun 2018 - 15:10

      Hi Grace, Your due date is 29th December 2018. Take care x

    • By Vee (not verified) on 10 Jun 2018 - 15:04

      Hi there I think I am around 5-6 weeks pregnant I found out around three weeks ago at the time I was a smoker but quit as soon as I had a positive pregnancy test , I have been trying to eat healthy to lots of fruit and veg when I'm not feeling nauseous but my BMI is 38 which puts me in the obese catagory and i have heard obesity can cause problems in pregnancy and birth I really would like to loose weight in a way that keeps my baby safe .. is there any advice on excersises or other ways to loise weight healthily during my pregnancy please? I am 29 x

    • By Midwife @Tommys on 11 Jun 2018 - 15:30

      Hi Vee, It is very important in your pregnancy that you attend all of your antenatal appointments. Try to eat a healthy balanced diet with at least 5 portions of fruit and vegetables every day and do a minimum of 30 minutes exercise each day. Your maternity team may be able to refer you to a dietician for help in managing your weight. You will also have a glucose tolerance test and advice on cutting down on your sugar intake. Try to cut down on snacks, particularly those high in sugar or carbs and drink water rather than any other drinks which are often high in glucose. Best wishes

    • By Elizabeth (not verified) on 7 Jun 2018 - 06:43

      my LMP was 1st of may and I found out that I am pregnant how many weeks now and when is my due date pls?

    • By Midwife @Tommys on 7 Jun 2018 - 15:06

      Hi Elizabeth, congratulations on your pregnancy.

      If your LMP was 1st May then you are around 5-6 weeks pregnant giving you an estimated due date of 4th February 2019. Hope this helps, take care, Tommy's Midwives x

    • By Anu (not verified) on 5 Jun 2018 - 08:23

      Hi i had my last periods on 12th April and now it's going to be about 8 week. Haven't take any pregnancy test however I am very excited about it. But today feeling stomach cramp and past few days feeling tired and taking naps every now and then. Last year July I had miscarriage after 5 week. Pls advice me what precautions must I take and when must I visit doctor

    • By Midwife @Tommys on 6 Jun 2018 - 12:23

      Hi Anu
      I would recommend that you do a pregnancy test to be 100% sure. If you have a positive test, you can see your GP to confirm the pregnancy, arrange for your antenatal care to start and to book in your first scan for 12 weeks gestation. You will also need to start taking folic acid and pregnancy vitamins if this is the case to help support a healthy pregnancy. If you are not pregnant, i would also recommend that you see your GP to review why your period is late and the symptoms you are having. You may need need to be sent for a gynecology review to put your mind at ease.
      Please take care and i wish you all the best
      Sophie, Tommy's Midwife

    • By Anu (not verified) on 6 Jun 2018 - 14:07

      Hi Sophie
      Thanks for your advice.
      I did visit GP today pregnancy test was negative he also did scan for me but nothing can be seen in there also. So my GP said I am not pregnant he was suggesting medicine for me so that I can get my periods or he say wait for it to come naturally. I want to wait another 2 weeks. My periods have never been so late so when pregnancy result was negative I was very sad. Anyway thanks for your advice. I really appreciate it

    • By Midwife @Tommys on 6 Jun 2018 - 14:30

      Hi Anu
      I am sorry to hear that it was not the result you were hoping for. But i am glad you are under the care of your doctor who will guide you through. All the best
      Sophie,Tommy's Midwife

    • By Merlene (not verified) on 4 Jun 2018 - 09:59

      I had unprotected sex without him releasing inside me on the 14 March, I got my period in March as normal and also in April but I didn't get it in May, to date I still didn't get it (04.06.18). My period is very regular, however, I did have irregular period before falling pregnant in 1995, which was because of fertility drugs. I couldn't fall pregnant thereafter and my periods were again irregular. its has been regular since 2004, I have been on the pill on and off, I did a pregnancy test on the 26 May, it was negative. Is there a chance that I could be pregnant, I am 47 years old

    • By Midwife @Tommys on 5 Jun 2018 - 14:16

      Hi Merlene,

      Thank you for contacting us. I think it would be best for you to contact your GP for a full assessment. Your lack of period may be hormonal due to use of the pill or it may be normal for you due to your history of irregular periods.

    • By Melissa (not verified) on 1 Jun 2018 - 05:02

      Had my last period on the May 8th. Took a test today May 31st. How many weeks do you think I am

    • By Midwife @Tommys on 1 Jun 2018 - 10:04

      Hi Melissa,
      We date a pregnancy according to the first day of your last period, therefore given the date of the 8th of May you would be about 3 weeks and two days pregnant if you have a regular 28 day cycle.
      Best wishes
      Tommy's midwife

    • By Stace (not verified) on 4 Jun 2018 - 13:29

      Hi I am currently 5 days late on my period me and my partner have new trying for 5 years i am very scared to take a test just incase it's not the answer I won't not really any pregnancy symptoms just really bad wind is this a sign of early pregnancy?

    • By Midwife @Tommys on 6 Jun 2018 - 12:28

      Hi Stace
      I would advise that you take a test when your period is 7-10 days late to get the most accurate positive or negative result. If you take a test too early, it can give a false negative result as the pregnancy hormones (hcg) have not yet had time to build up in your system to be shown by the test.
      If the test is negative and your period is still late, then i would recommend that you go to your GP for a review and explain that you have been trying to conceive for 5 years. They may send you for a gynecology review and request some bloods are taken from you to start the ball rolling.
      Bad wind isn't an obvious sign of early pregnancy, it is just too generic to know without doing a test.
      I wish you all the best
      Sophie, Tommy's Midwife

    • By Jazmin (not verified) on 1 Jun 2018 - 04:33

      Hello I'm Jazmin, I have currently missed my period it's already 5 days late should I take a pregnancy test or should I wait longer? My period was supposed to be 5/25/18

    • By Midwife @Tommys on 1 Jun 2018 - 09:57

      Hi Jazmin,
      If you are five days late on your period and have been having intercourse then yes it would be fine to take a pregnancy test now.
      If you are trying to conceive then, if you are not already, we would advise for you to be taking a folic acid supplement.
      Best wishes
      Tommy's midwife

    • By Sahitya (not verified) on 30 May 2018 - 03:05

      My last period was 25th April now 6 days late period,pregnancy test was negative on 4th day in hospital so doctor conducted blood test and thyroid test.Thyroid was normal but prolactin was 39 but i have pregnancy symptoms .please let me know whether i take medication for this

    • By Midwife @Tommys on 1 Jun 2018 - 09:55

      Hi Sahitya,
      If you are not pregnant then I am afraid that we would be unable to advice whether you need medication or not as raised prolactin levels can be due to several things. If you feel that you maybe pregnant, the prolactin levels rise in pregnancy so this would be very normal and there would be no need for medication. You may want to repeat your pregnancy test in a few days if you continue to have symptoms. Otherwise I hope you have a follow up with your doctor.
      Best wishes
      Tommy's midwife

    • By Kyushu Gor (not verified) on 1 Jun 2018 - 13:32

      My last periods were on7th May so How could I know Am I pregnant or not because always 1 week prior my periods come

    • By Midwife @Tommys on 1 Jun 2018 - 16:53

      Hi Kyushu,
      You won't necessarily know unless you are getting very obvious symptoms. A pregnancy test at this stage may not detect a pregnancy as your hormone level may not yet be high enough. I would advise to wait, and if your period does not come when due then to take a pregnancy test. In the meantime if you are trying to conceive then it is important to be taking a folic acid supplement.
      Best wishes
      Tommy's midwife

    • By China (not verified) on 29 May 2018 - 18:14

      I had my last period on 17 April, how many weeks am i?

    • By Midwife @Tommys on 30 May 2018 - 16:08

      Hi China
      Using your last menstrual period date of 17th April, the most pregnant you would be is around 6 weeks.
      When you go for an ultrasound scan, they will measure the baby and give you a more accurate gestation and due date.
      Congratulations. Sophie,Tommy's Midwife

    • By s mummy (not verified) on 29 May 2018 - 16:46

      I done a clear blue on the 26-5-18 and says I'm 3+ weeks. I don't know the last period I had I just need more information. Can you help?

    • By Midwife @Tommys on 30 May 2018 - 16:11

      Hi S Mummy
      Without knowing the date of your last period, it is impossible to date your pregnancy. To do this accurately, you'll need to go for an ultrasound scan. There they will measure the fetus and give you a current gestation and estimated due date. Your GP can arrange this for you at your local hospital.
      All the best
      Sophie,Tommy's Midwife

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