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 Midwife @Tommys on 4 Jul 2018 - 15:55

    Hi Pooja
    Using your last menstrual period of 30/5/18 you are no more than 5 weeks pregnant exactly today.
    Please see your GP to book for maternity care/ultrasound scan or to review your options. Please take care
    Sophie,Tommy's Midwife

  • By Lisa (not verified) on 2 Jul 2018 - 18:38

    5 weeks pregnant and experiencing lower abdominal pain once at night , had ultrasound done internal os closed
    Ps: pain on lower leftside

  • By Midwife @Tommys on 3 Jul 2018 - 13:58

    Hi Lisa,
    I assume that the ultrasongrapher or doctor saw a gestational sac at your scan?
    Mild aches and pains are common in pregnancy. Sharp twinges and pulling or pinching sensations when you move are most likely to be ligament pain (in the pelvic or groin area and either side of belly button). Hormonal changes cause the ligaments which support your organs and growing uterus to soften and stretch.
    Usually change of position, rest and a warm bath or applying a heat pad will help to ease this discomfort. The discomfort should only be mild and occasional. Some women also experience mild cramping pains in pregnancy - this is due to increased congestion of blood in the pelvic region and the release of hormones called prostaglandins - which usually cause period pain during menstruation. Again this pain should only be mild and occasional - and improve with rest and heat. You may be feeling extremely tired or have mild ligament pain - these are also ongoing pregnancy symptoms. Occasionally such symptoms settle or stop early around 8-9 weeks rather than at the end of the first trimester.
    Please keep an eye on the pain if it were to become extremely painful with vaginal bleeding please see your GP, or out of hours call 111 for advice.
    I hope this helps. If you are feeling worried you can always call the midwives on 0800 0147 800
    Warmest wishes
    Anna-Tommy's Midwife

  • By Tash (not verified) on 2 Jul 2018 - 15:50

    My last period started 27th May
    Took a test yesterday but only seeing doctor end of July
    How far could I be right now?

  • By Midwife @Tommys on 2 Jul 2018 - 16:27

    You are 5 weeks now with due date March 3rd 2019.

  • By Jenni (not verified) on 2 Jul 2018 - 10:11

    I did a urine pregnancy test that came out two lines. Pls How many weeks pregnant am I?

  • By Midwife @Tommys on 2 Jul 2018 - 15:37

    You are 5-6 weeks pregnant now with due date 1st March 2019.

  • By Rossi (not verified) on 1 Jul 2018 - 23:41

    I never got my period on April 20th how many weeks I am ?? I took a test on may 9th and it showed positive also can you help me find a good place to go to get a check that doesn't cost alot here ion Scottsdale

  • By Midwife @Tommys on 2 Jul 2018 - 15:34

    With your LMP (last menstrual period) being 20th April you would be about 10 weeks pregnant now. Due date is January 26th 2019. I am afraid I don't know where Scottsdale is so won't be able to help you with arranging your care. If you are in the UK you should go to see your GP.

  • By Rainbow Pregnancy (not verified) on 28 Jun 2018 - 19:52

    Hi - I had my first u/s on Monday where I was supposed to be exactly 6 weeks 0 days and a heart rate of 98 bpm was detected. I had a m/c earlier this year and I am worried that this rate is low. My fertility also said that it is somewhat smaller than 6 weeks although did not comment further. She said there is 50/50 chance of it going wither way. I am just looking for a second opinion and some assurance. I am going back tomorrow for a follow up u/s :)

  • By Midwife @Tommys on 29 Jun 2018 - 11:50

    I am sorry to hear that you have experienced a miscarriage and this pregnancy is seeming very uncertain at the moment. I am afraid it is difficult to know the future of this pregnancy but it is great that you are being followed up and monitored regularly.
    If we can support you then please do be in touch.
    Wishing you all the very best
    Tommy's midwife

  • By hope (not verified) on 23 Jun 2018 - 17:43

    my last period was on 19-22 February 2018

  • By Midwife @Tommys on 25 Jun 2018 - 14:11

    By these dates your pregnancy is now in week 18. Have you visited your doctor or midwife yet?

  • By bethanyallen (not verified) on 22 Jun 2018 - 16:41

    i took a pregnancy test and it came back positive but i dont no roughly how far i am as me and my fiance cant remember when i was on last how can i find out how far i am i dont see the midwife until the 2nd july

  • By Midwife @Tommys on 25 Jun 2018 - 14:09

    Your pregnancy will be dated when you have your scan. This is usually from 11-14 weeks. You will be given a due date at this appointment.

  • By Claire Lim (not verified) on 22 Jun 2018 - 15:11


    I have an irregular period usually delayed for 3-4days and the latest is 3 weeks. My LMP was last April 20th ended 25th and now it's been 2 months and I haven't gotten my period still within the span of those weeks I have been having intercourse. Is it possible that I'm pregnant?

  • By Midwife @Tommys on 22 Jun 2018 - 15:34

    Hi Claire,
    It is possible that you are pregnant however you would need to take a pregnant test to confirm this.
    Best wishes
    Tommy's midwife

  • By Emma (not verified) on 22 Jun 2018 - 13:22

    Hi I ovulated 1-4 June I was due to have a period on the 18th June but I started to bleed on the 14th but only lasted 2 days and I’m normally regular also have been taking tests we have had positive and negative ones I’m confused with what’s happening am I pregnant

  • By Midwife @Tommys on 22 Jun 2018 - 15:32

    Hi Emma,
    It is difficult to know for sure, we do take any positive test as a pregnancy, it could be that the different tests have different sensitivities. We would take it as you are pregnant but it may be useful to see your GP for a blood test to confirm your pregnancy.
    Best wishes
    Tommy's midwife

  • By mmoho (not verified) on 22 Jun 2018 - 02:41

    I slept with my boyfriend in April and the whole of May I didn't see my period but in June I saw them could it be that I'm pregnant im experiencing sudden change in my belly yet I toke a pregnancy test twice but it gives me one line and not two

  • By Midwife @Tommys on 22 Jun 2018 - 15:30

    Hi Mmoho,
    It maybe that it is a little soon to do a pregnancy test, if you had a period in June and had intercourse since then I would advise for you to wait to see if your next period comes, and if not then to take pregnancy test. If you keep having negative tests and your period does not come then do see your GP for a review.
    Best wishes
    Tommy's midwife

  • By Ana (not verified) on 21 Jun 2018 - 07:43

    Hey my period was due on 17 may but i didnt bleeded n i got implantation bleeding about 2 weeks ago and im having morning sickness, a bit nausea, pain in tummy, mood swings and body aching. Is it normal? so how many weeks i could be pregnant ?

  • By Midwife @Tommys on 21 Jun 2018 - 16:39

    Dear Ana,
    I would need the date of the first day of your last period to be able to work out how many weeks pregnant your are. your pregnancy symptoms sound very normal but if you have any pain and/bleeding then do be in contact with your GP for a review.
    Best wishes
    Tommy's midwife

  • By Elsie (not verified) on 20 Jun 2018 - 06:54

    My last period was on 24 February 2018

  • By Midwife @Tommys on 21 Jun 2018 - 16:36

    Dear Elsie,
    From the dates that you have given, if your cycle is 28 days and regular, then your baby will be due about the 1st of December. You will have a dating scan when you are 12 weeks pregnant which will give you your actual due date.
    Best wishes
    Tommy's midwife

  • By Jem (not verified) on 18 Jun 2018 - 20:20

    I stopped taking the contraceptive pill on April 14th, I haven’t yet had a period (they were irregular before I went on it) and I took several pregnancy tests today June 18th and all came up pregnant with the weeks estimator one saying 3+ weeks. Hubble and I have been trying from when I stopped the pill but worried it could be a false positive and not having had a period yet I have no idea about possible conception date.

  • By Midwife @Tommys on 21 Jun 2018 - 16:47

    Dear Jem,
    It sounds like it is very difficult to be able to date the pregnancy and you only have the pregnancy test of 3+ to go off. It is very unlikely to be a false positive however you could see your GP for a blood test to confirm the pregnancy. You would need to have a scan to date the pregnancy, this is done about 12 weeks, it should be take from when you came off the pill if you have not had a period but they may need to re-scan if necessary.
    Best wishes
    Tommy's midwife

  • By Shay (not verified) on 17 Jun 2018 - 16:27

    I had my period on the 21st of May and ended up on 24th. I think I ovulated on June 1 to 7 so Me and my partner make love. On june 11 I've noticed a light pink/brownish spot on my undies and git a headache and nausea so I tried HCG Test and it was negative. On june 12 we make love again, then I saw a spot of blood again after we did sex. I drink milk every morning but sometimes in the afternoon I'm taking softdrinks, I ate crabpaste, etc. does the food I took will affect the baby(if)? The next day up to this day, I feel nothing. I took my test again on June 16 and it came out negative again. My due will be on June 18. I want to know if I am a sure pregnant since i've experience the so called implantation bleeding. Thank you!

  • By Midwife @Tommys on 21 Jun 2018 - 13:46

    Hi Shay, Thank you for your comment.

    If your period isn't due until the 18th June, you may be testing too soon so we would recommend that you wait and see if you miss your period, if this happens then test again, if it is still negative and your period has not come and you are actively trying for a baby then see the GP as they can do a blood test which checks for the pregnancy hormone. Hope this helps, Take Care Tommy's Midwives x

  • By glaiza (not verified) on 17 Jun 2018 - 08:50

    hi i had my checkup yesterday and it turns out to be positive, this is a honeymoon baby! my lmp is april 14-19. do you know when is my duedatw

  • 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

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