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 Sindhu Siva (not verified) on 12 Jul 2018 - 18:46

      Thanks for the reply:-)

    • By krp (not verified) on 12 Jul 2018 - 03:37

      My last period was June 16th. Had intercourse on June 27-28. Tested positive today 7/11.

    • By krp (not verified) on 12 Jul 2018 - 17:34

      when is my due date

    • By Midwife @Tommys on 13 Jul 2018 - 13:38

      You have not provided any dates therefore I am unable to advise when your baby is due, you can use our calculator to work out your dates if this helps:
      Best wishes
      Tommy's midwife

    • By Amal (not verified) on 7 Jul 2018 - 07:07


      my LMP was 25/5/2018 i tested both blood and urine and it was positive I recently did an u/s and the DR said there was no Foetal pole, he said come back again after 2 weeks for another U/s your pregnancy is positive but can't see now
      so when i should go whats my pregnancy weeks dua date

    • By Midwife @Tommys on 9 Jul 2018 - 15:50

      It is best to wait for the next USS before trying to date your pregnancy. Sometimes the pregnancy doesn't develop as expected and sometimes the dates are incorrect. Until your next USS it isn't possible to know what is happening.

    • By Christine (not verified) on 5 Jul 2018 - 09:07

      I had my periods 2 times in may Dat was at the beginning of May and the second one on 19-21 may. I didn't see my periods in June, I tested positive on 30th june

    • By Midwife @Tommys on 5 Jul 2018 - 15:34

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

      If the first day of your last period was around the 19th May then you should be around 6-7 weeks pregnant. Going from the dates that you have given, conception may of occurred at the beginning of June. If you are unsure of your dates then it is advisable to go and see your GP who should be able to refer you for an early dating scan then you will know for sure. Hope this helps, Take Care, Tommy's Midwives x

    • By Amy (not verified) on 4 Jul 2018 - 14:51

      HELP PLZ
      I did a pregnancy test 3 times yesterday 3/7/18 and its positive. But my ladt period was from 6 to 10/6/2018 i didn't have intercourse untill the 17/6/ 2018. How can i be pregnant? and how many weeks am i? am confused because i had an ectopic 2016 November . And am panicking. Help HELP plz

    • By Midwife @Tommys on 4 Jul 2018 - 15:53

      Hi Amy
      Using your last menstrual period date of 6th June, the most pregnant you could be is 4 weeks pregnant today. But if you had intercourse on the 17th June, then you may only be 2-3 weeks pregnant max
      Only an Ultrasound scan can accurately date the pregnancy by correlating your last menstrual period date and the baby's growth.
      Please visit your GP to get your maternity care/ultrasound scan booked and/or to review your options.
      All the best
      Sophie, Tommy's Midwife

    • By Me (not verified) on 4 Jul 2018 - 14:11


      I had a miscarriage early this year and went on contraceptives,they treated me badly and I got off them I recently did an u/s and the DR said there was no Foetal pole,she did a round of blood tests and said I must come back again for another U/s m very nervous and needed a second opinion.

    • By Midwife @Tommys on 5 Jul 2018 - 14:13

      Hi, Thank you for your comment.
      It is normal practice that if you are very early in your pregnancy then it can be difficult to see anything on scan as the pregnancy is so small. The Dr is right is asking you to come back in a few days to have another scan, this way they will of given enough time for the pregnancy to have grown, they will expect to see something on the next scan. It can be a nervous wait when you want answers but try and stay calm while you are waiting for your blood results and scan. If you have any concerns then please contact your local early pregnancy unit. Take Care, Tommy's Midwives x

    • By stella obi (not verified) on 4 Jul 2018 - 09:51

      I had sex wit my boyfriend on d 19/04/2018 and my LMP was 12 April pls when is my due date and many weeks pregnant

    • By Midwife @Tommys on 4 Jul 2018 - 16:05

      Using your LMP of May 12th, you would be no more than 10-11 weeks pregnant today. This will be confirmed on ultrasound scan alongside fetal growth.
      All the best
      Sophie,Tommy's Midwife

    • By Anonymous (not verified) on 4 Jul 2018 - 23:04

      tanks ma I appreciate

    • By Mahsa (not verified) on 3 Jul 2018 - 19:42

      Last Period Start Date: May 15
      Ovulation Test: YES on May 26
      Intercourse May 26, 27 and 28
      Tested Positive on June 14

      How many weeks am I now?

    • By Midwife @Tommys on 4 Jul 2018 - 16:03

      Hi Mahsa
      Using your last period date of 15th May and presuming you have a 28 day cycle- your would be approx 7 weeks pregnant today. This might change slightly ( most likely to be a little less far along than that) when you go for your scan allowing for adjustment between fetal growth and your period date.
      All the best
      Sophie,Tommy's Midwife

    • By Neo (not verified) on 3 Jul 2018 - 15:59

      Hi. I last saw my periods on the 17 May. And I had unprotected sex on the 1&2 June and I drank morning after pills on the 3rd but they didn’t work. I was suppose to get my periods on the 11th June but didn’t get them and my boobs started getting tender and heavy so I took a pregnancy test it showed a positive result. So how many weeks am I?

    • By Midwife @Tommys on 4 Jul 2018 - 15:59

      Hi Neo
      using your LMP of 17th May, the most pregnant you could be is approx 7 weeks, but since you can pinpoint when you had intercourse, you are more likely to be around 5 weeks pregnant approx.
      Please visit your GP to book in for your antental care/ultrasound scan/ to review your options.
      All the best
      Sophie,Tommy's Midwife

    • By Pooja (not verified) on 3 Jul 2018 - 15:53

      My last period date was 30 may .today i check and two lines are shown . how many days i am pregnent

    • 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

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