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

Hide details

    Last reviewed on June 28th, 2018. Next review date June 28th, 2021.

    Was this information useful?

    Yes No


    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 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!

    • By Midwife @Tommys on 5 Nov 2018 - 11:59

      Hi Mary
      You will need to do a pregnancy test to know for sure. It is best to test 7 days after your period was due. See below for more tips when taking a pregnancy test to get the most accurate result.
      All the best
      Tommy's Midwife

    • By Temmygold (not verified) on 29 Oct 2018 - 17:29

      I saw my period last on the 2nd of Oct, was expecting the next one. I had some on and off cramps and a missed period so I did a urine test at home, it came out positive so I went to the hospital to confirm and it came out positive..
      What is the next thing for me to do presently?

    • By Midwife @Tommys on 2 Nov 2018 - 09:57

      Hi Temmygold,
      When you find out you are pregnant, if you are not already, it is really important that you start taking a folic acid and vitamin D supplement. Then when you are ready, you can either contact your GP for a referral to maternity services, or most hospitals now you can also self refer online on the hospital's website. Once this referral has been processed, then you be well be sent an appointment for your first booking appointment with the midwife, then they will make a plan with you then for your antenatal care.
      Best wishes
      Tommy's midwife

    • By Aminat (not verified) on 29 Oct 2018 - 15:08

      My lmp was September, 18 doctor confirmed am pregnant am one wk pregnant since den am always feeling discomfort in my belly n on liquid paraffin due to my history up till now is it save

    • By Midwife @Tommys on 2 Nov 2018 - 09:51

      Hi Aminat,
      Liquid paraffin can be prescribed in pregnancy to soften your stools and help with constipation, it is also really important to make sure that you are drinking enough water and having lots of fruit, vegetables and high fibre foods, together with some regular exercise. If you are constipated then this can cause some discomfort, however if you are in pain or this is on going then do go back to your doctor.
      Best wishes
      Tommy's midwife

    • By Zari (not verified) on 22 Oct 2018 - 17:00

      Hi my LMP was on 20/21 of September 2018. I have a 28-30 day cycle. depending on the flow of my periods. Today the 22nd October 2018 I found out that I’m pregnant. My Best friend and I had already make plans to travel to Singapore and Bali from the 4-12 November 2018. Is it safe to travel abroad from India. I have no symptoms of morning sickness or feeling of tiredness or nausea so far and I travel by road from home to work on a weekly basis for six hours and did the same today. I sometimes have to travel for 8 hours depending on my work. Pls tell me whether it is safe to travel? I am a 36 year old woman.

    • By Midwife @Tommys on 23 Oct 2018 - 14:13

      Yes, it is safe to travel in pregnancy as long as you are healthy. Be cautious of drinking local water if you are abroad as you are not used to it. We recommend bottled water instead. We have good travel advice here

    • By Kate S (not verified) on 11 Oct 2018 - 22:45

      I am 5 weeks pregnant and today have sharp stabbing pain on my left side that comes and goes. No blood but worried something is going wrong. What should I do?

    • By Midwife @Tommys on 15 Oct 2018 - 12:29

      Hi, I hope that your pain has settled down now. Sorry not to be able to respond earlier. If you are still concerned please see your GP or if you are in serious pain you can go to A/E.

    • By Elsie (not verified) on 11 Oct 2018 - 19:01

      my last period was between 20 and 25

    • By Midwife @Tommys on 12 Oct 2018 - 16:56

      Hi Elsie,
      According to your dates, your baby will be due about the 28th of November, however you should have been given a due date when you had a scan during the first trimester of your pregnancy.
      Best wishes
      Tommy's midwife

    • By Rachel (not verified) on 10 Oct 2018 - 20:31

      I don’t remember the last date of my period, i have been irregular for a while due to the pill.
      When I go to my first midwive appointment will they give me a scan to see how far along I am because I’m unsure of the date or will they wait & book me in for another at a later date?

    • By Midwife @Tommys on 11 Oct 2018 - 12:29

      Hi Rachel, Thank you for your comment.
      If you are unsure of your dates then you don't have to wait to book with the midwife, the GP can refer you for an early dating scan to give you an accurate idea of how many weeks you are. Please call your GP to arrange this. Take Care, Tommy's Midwives x

    • By Shanice (not verified) on 4 Oct 2018 - 04:40

      Hi, I'm 7 weeks pregnant and I'm wondering in what order should I start planning things? I just don't want time to start going fast & I'm not prepared. Besides going to the doctor, when should I start buying baby stuff, saving up and thinking of baby names, ect??

    • By Midwife @Tommys on 8 Oct 2018 - 14:45

      Hi Shanice, Why not follow our pregnancy guide week by week. This should cover all your queries at just about the right time. Saving up of course starts now! and you should see your doctor straight away- or as soon as you get an appointment, but there is no rush to buy anything yet. Take care

    • By Dionna (not verified) on 28 Sep 2018 - 15:20

      I’m 11 weeks pregnant and I can say I only had 2 or 3 days out of my pregnancy no sickness but ever since I found out at 6 weeks I been SICK sore boobs tired and also throwing up mornings and nights ... is this normal I actually don’t feel so

    • By Midwife @Tommys on 1 Oct 2018 - 14:27

      Hi Dionna, Unfortunately this is completely normal. We understand how difficult it can be and for most women this begins to resolve around 12-14 weeks when they start to feel much better. Hope it does for you too. Best wishes

    • By Dora (not verified) on 28 Sep 2018 - 14:56


      I’ve had my last period between 11-14 of aug. i missed my period that supposed to be on the 10th of sept, and afterwards i was keep doing doing pregnancy tests but all said neg, and on the 14th day of missed period (25th of sept) :) i got 2 lines on my test, when i was just about to give up. I am so happy and thankful, and i would like to ask how many weeks pregnant I am? It might have happened when my period was on due?!
      Thank you!

    • By Midwife @Tommys on 1 Oct 2018 - 14:32

      Really pleased for you Dora and hope that you have a happy and healthy pregnancy. I can't be sure about your dates if your periods are irregular, but the best way to confirm is to have an early pregnancy scan.
      If you were doing regular pregnancy tests and first positive on 25th Sept I would suspect that you would be 9 weeks now. Take care

    • By Peace (not verified) on 27 Sep 2018 - 13:51

      My last period was 17/08/18,a week ago I was confused pregnant, please how many weeks am I now?

    • By Midwife @Tommys on 27 Sep 2018 - 15:30

      Hi Peace, Thank you for your comment.

      If your LMP was on the 17th august then you should be around 6 weeks pregnant. Hope this helps, take care, Tommy's Midwives x

    • By Anonymous (not verified) on 27 Sep 2018 - 13:02

      My partner n I had unprotected sex and the last time I seen my period was July 28, 2018. How many weeks am I and I'm afraid to take a pregnancy test. What should I do?

    • By Midwife @Tommys on 27 Sep 2018 - 15:06

      Hi, Thank you for your comment.

      If you are pregnant then you should be around 8-9 weeks pregnant. It would be advisable to do a pregnancy test to see if you are pregnant and then see you GP for further advice. Hope this helps, take care, Tommy's Midwives x

    • By Lauren (not verified) on 27 Sep 2018 - 07:34

      Mykast period was the 12th of august, i did 3 tests a couple of days after and they were all positive. How far gone am i ?

    • By Midwife @Tommys on 27 Sep 2018 - 15:20

      Hi Lauren, Thank you for your comment.

      If your LMP was the 12th August then you are around 6-7 weeks pregnant. Hope this helps, take care, Tommy's Midwives x

    • By Parvin (not verified) on 19 Sep 2018 - 12:33

      Hi I started my period last month 15th August since then I haven't started my period I did have unprotected sex with my husband few time and do pregnancy test it still shows negitive I contact my gp and they said to wait but I did have few miscarriage and ectopic pregnancy in the past and was with the hospital miscarriage specialist but no longer with them they did say I have chance to be pregnant and now I am not starting my period still shows negitive my body is changing too. So what do i do now. Thank you

    • By Midwife @Tommys on 21 Sep 2018 - 11:25

      Hi Parvin, If you are planning a pregnancy, what about trying our new pregnancy tool.
      This is a simple way to see if there are any lifestyle changes you could make to help you to conceive and maintain a healthy pregnancy.
      If you have repeated negative pregnancy tests it is extremely unlikely that you are pregnant at this time although I agree with your GP that it is still very early and if you ovulated late your period may still come any day. Take care.

    • By Anonymous (not verified) on 19 Sep 2018 - 04:48

      Every app asks when was the last menstrual cycle, honestly I'm too sure, the day of intercourse was July 28th. How am I supposed to calculate due date?

    • By Midwife @Tommys on 20 Sep 2018 - 15:04

      Hi Thank you for your comment.
      The app should be asking for the first date of your last period, so this should be around 14 days before ovulation. If you are unsure of your dates then we would suggest that you see your GP who can refer you for a dating scan to see how many weeks your are. Hope this helps, Tommy's Midwives x

    • By Pau (not verified) on 18 Sep 2018 - 15:10

      Would like to ask on August 17, 2018 my partner and i didnt have sex but just fooled around he didnt came inside me and just came near my right leg and nearly in my vagina. After that I had my heavy period - 6 days on august 21,2018. My next period should be today, Sept 18,2018 but didnt have it, my boobs are sore and I have cramps and lower back pains, I tried pregnancy test 1 day before my period it was negative, but today been waiting for my period to come but it didnt am I pregnant?

    • By Midwife @Tommys on 20 Sep 2018 - 14:18

      Hi Pau, Thank you for your comment.
      It is unlikely that you are pregnant as you had a heavy period after this incident happened and then you have had negative pregnancy tests. It sounds like your period is a little late this cycle. If you are still worried and your period doesn't come then take another pregnancy test and if it is still negative please see your GP who can do a blood test to check for the pregnancy hormone. Take Care Tommy's Midwives x

    • By Carol (not verified) on 18 Sep 2018 - 09:56

      LMP was on 24,25,26 many weeks am i?

    • By Midwife @Tommys on 20 Sep 2018 - 14:07

      Hi Carol, Thank you for your comment.
      If your LMP was the 24th March then you should be around 26 weeks now. If you have any concerns then please contact your GP or midwife who will be able to advice your further. Take Care, Tommy's Midwives x

    • By Melissa (not verified) on 13 Sep 2018 - 21:37

      My last period was 2nd August 2018 and I had a positive pregnancy test 2 weeks ago. I have had symptoms on and off, sore boobs, cramps, pulling sensation, stitch feeling. I am nervous when the pains are there that things are going wrong but then when they stop I get nervous until they start again. Is that all normal, should I be feeling things on and off? Thanks x

    • By Midwife @Tommys on 14 Sep 2018 - 11:47

      Hi Melissa,
      It is very normal for symptoms to vary, they can be different for each woman, each pregnancy and throughout the pregnancy. Feeling sore boobs and having some mild cramps are very common early pregnancy symptoms. If you find that the cramps are painful or if you have any bleeding then I would advise for you to see your GP just to make sure everything is ok with the pregnancy.
      Best wishes
      Tommy's midwife

    • Pages

    Add new comment