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 14 Jun 2017 - 11:42

      Hi Zuri,
      Please get seen by your doctor or midwife today as you are already coming to the end of your first trimester and need to start antenatal care as soon as possible. you need to know what your options are in regards to scans and blood tests. Going to the loo so many times may just be due to early pregnancy but I would want to check that you haven't got a urinary tract infection as well. You can also call us here at Tommy's and talk to a midwife on 0800 0147 800 or email us on [email protected]
      Hope to hear from you soon
      Anna-Tommy's Midwife

    • By Rosy (not verified) on 13 Jun 2017 - 19:06

      My last period was on 27th April, on 25th may I saw period for a day and half and I had unprotected sex this two months. Please am I pregnant. Am afraid to do pregnancy test.

    • By Midwife @Tommys on 14 Jun 2017 - 10:36

      Hi Rosy,
      If you have been having unprotected sex over the last two months it is possible that you are pregnant. You mention a period but this seems very short lasting.
      I appreciate that you are feeling frightened but if you don't do a pregnancy test you won't know whether or not you are pregnant and if you are you can get support and find out what options are available to you. Please buy a test today and call us if we can be of any support to you on 0800 0147 800.
      Anna - Tommy's Midwife

    • By Rosy (not verified) on 13 Jun 2017 - 18:12

      My last period was on 27th April, on 25th may I saw period for a day and half and I had unprotected sex this two months. Please am I pregnant. Am afraid to do pregnancy test.

    • By Anonymous (not verified) on 8 Jun 2017 - 11:51

      I saw my last period on d 3rd of May 2017,always 28days.And in June 5th i saw it again is it possible to be pregnant?pls help me easy my worries.

    • By Midwife @Tommys on 8 Jun 2017 - 12:03

      Hi, if you have not missed a period then you shouldn't be pregnant. If the period that you have had in June was a normal period for you, then again you may not be pregnant. If you have been having unprotected sex then there is a chance of a pregnancy but you have not missed a period so the likelihood of you being pregnant is relatively low. That's not to say that in some cases women don't miss a period or have some bleeding and they are pregnant. If you think that you may be pregnant then you can always take a pregnancy test, but again you haven't missed a period, so being pregnant is highly unlikely. Hope this has reassured you a little. Take Care, Tommy's Midwives x

    • By Anonymous (not verified) on 5 Jun 2017 - 05:33

      Hi I am trying to get pregnant for the longest while I did an ultrasound and it shows all my organs are good in shape and size what is going wrong I had sexual I intercouse to with my husband the day after my last cycle finish can I get pregnant that way or will I become pregnant

    • By Midwife @Tommys on 5 Jun 2017 - 11:53

      Hi. How long have you been trying to get pregnant? In the UK we recommend that couples try for a year before we suggest that they see a doctor for advice. Have you seen our page on 'getting pregnant' ? It may help.

    • By Nkiruka Chiemezie (not verified) on 30 May 2017 - 12:57

      If my last period was on the 18th of april,how many weeks pregnant am i?

    • By Midwife @Tommys on 31 May 2017 - 11:21

      Hi Nikiruka
      Congratulations of your pregnancy. Using the link below, you can enter the 18th april as your last menstrual period date, as well as the average length of your cycle to work out roughly how many weeks pregnant you are and to get your estimated due date. Please take good care of yourself!

    • By victoria makena (not verified) on 29 May 2017 - 19:10

      hi i saw my last period on 28 april when i went for a test on 27 may i was pos so how many weeks is my pregnant thenks

    • By Anonymous (not verified) on 25 May 2017 - 14:34

      I want to know how many weeks pregnant I am.I saw my period last on April 8.

    • By Midwife @Tommys on 25 May 2017 - 16:37

      Hello! If the first day of your last period was on the 8th April, then you are nearly 7 weeks pregnant. If you have had a positive pregnancy test then you need to see the GP, who can refer you to the midwife. Take care Tommy's Midwives x

    • By Midwife @Tommys on 31 May 2017 - 11:12

      Hi, using the link below, you can work out your estimated due date and roughly how many weeks pregnant you are by using your last menstrual period date of the 8th april, and putting in your average menstrual length cycle. Congratulations!

    • By Midwife @Tommys on 31 May 2017 - 11:12

      Hi, using the link below, you can work out your estimated due date and roughly how many weeks pregnant you are by using your last menstrual period date of the 8th april, and putting in your average menstrual length cycle. Congratulations!

    • By Anonymous (not verified) on 15 May 2017 - 21:51

      I've just found out I'm pregnant but unsure of how far gone I am. I had a 4 day mens cycle (which is normal) march 2017 and a day and 1/2 mens cycle at the beginning of April. Gp doesn't know how many weeks I could be , midwives haven't been in contact. Any ideas?

    • By Midwife @Tommys on 17 May 2017 - 09:27

      Hi there.
      It might be necessary to date your pregnancy via Ultrasound scan if your dates are uncertain.
      You can try our pregnancy calculator - see link below- using your last menstrual period date as your april period, and give your average length of menstrual cycle. That will give an estimation of how many weeks pregnant you might be. But an ultrasound scan will be more accurate.
      You can contact your local midwifery service via your local hospitals website if you have still not got a midwife booking appointment and you are concerned.
      Please take good care of yourself

    • By Anonymous (not verified) on 12 Jun 2017 - 14:12

      I had my period on 28 April bt May I did nt got intil me my period nvr come why everybody reply I need to knw

    • By Midwife @Tommys on 12 Jun 2017 - 14:32

      Have you done a pregnancy test? If your periods are regular and you have had unprotected sex there is a chance that you could be 6 weeks pregnant. An ultrasound scan would confirm your dates. Glad that you have found our site. Please look after yourself and follow the health advice that we provide. Best wishes

    • By Anonymous (not verified) on 14 May 2017 - 15:22

      um pregnant n I want to know he far I am .I had my last period on the1st of April so how far can I be

    • By Midwife @Tommys on 15 May 2017 - 11:01

      We use the last menstrual period to calculate your due date. If this was April 1st your due date will be 7th January 2018 making you 6 weeks plus 2 days today. Your first scan appointment will confirm the date for you.

    • By Anonymous (not verified) on 13 May 2017 - 18:33

      Hello I'm 37 and have PCOS. It took 3 years and IVF to conceive my 19 month old daughter, who I still breastfeed twice a day. I developed post natal hypothyroidism. I recently started metformin to TTC. Today by some miracle I got a positive home pregnancy test-I am 4w4d. This week I also got a call from the doctors telling me to reduce my thyroxine as I've gone hyperthyroid now. TSH 0.07, T4 19.2 and T3 4.4. It'll take 4 weeks for my reduced size to take effect. My sister has had two miscarriages (you have helped her, thank you) and has just been found to be hyperthyroid. Whilst I am over the moon and staggered that I have conceived naturally, I am so anxious about miscarriage. I've had very light brown (barely a tint) discharge since 10dpo and I had one red spot at 10dpo. All pregnancies are precious and this one is a miracle to me - I need to know what I can do to ensure my thyroid levels don't risk my pregnancy. I've some progesterone left over from IVF so I'm going to use them up for the next week. Also, should I stop breastfeeding my daughter? Thank you so much-it's Saturday so my doctors are shut (and are not great with endocrinology or fertility issues)

    • By Midwife @Tommys on 15 May 2017 - 13:12

      Hello and congratulations on your pregnancy. I would suggest that you make an appointment to see your GP as soon as possible and discuss the thyroid levels in the context of the pregnancy.
      In the mean time I cannot advise that you take the progesterone tablets that you have left over. Although the BNF states that these tablets are not known to be harmful, studies have shown that progesterone tablets do not really prevent miscarriage. In addition the medication may require storage in a fridge or cool area to maintain it's potency. In a spontaneous pregnancy it is thought that the ovaries will produce enough progesterone to maintain the pregnancy naturally.
      How lovely that you are still feeding your daughter. You can continue with this for as long as you and she wants to. You may find of course that she instinctively stops on her own. Some people believe that the taste changes in a pregnancy and the toddler no longer wants to feed. All the best Tommy's midwives x

    • By Anonymous (not verified) on 12 May 2017 - 14:43

      Hi,my last period was on 12th April and lasted for 3days which is not suppose to be so,my period normally last for 5days,untill now i hve not seen my period till now which suppose to come on the 11 (bin yesterday),i don't know if am pregnant cos feeling fuller nd bloat....though,i've not done d pregnancy test....
      But,could it be am pregnant?

    • By Midwife @Tommys on 15 May 2017 - 12:38

      Sometimes periods can be irregular and this is not something to worry about but if you think you could be pregnant I would suggest that you do a pregnancy test to confirm either way. x

    • By Nancy (not verified) on 10 May 2017 - 07:42

      I had my last menses around 4th April 2017 and ended on the 10th of April... I have not seen my menses this month and today is 10th May will it be a pregnancy because I tasted positive when I did a
      home test old is the pregnancy now

    • By Midwife @Tommys on 10 May 2017 - 09:21

      Hi Nancy,
      Using our pregnancy calculator below, you can find out roughly how many weeks you are by putting in the date of the first day of your last menstrual period, as well as your average length of menstrual cycle- this will calculate a rough due date and how many weeks pregnant you are currently.
      Congratulations! Please do take care of yourself!

    • By Lesley (not verified) on 7 May 2017 - 18:56

      I have very recently found out I am pregnant after several attempts at IVF. I am 38 and currently 4wks 3days pregnant. I had a missed miscarriage at 10 weeks in Jan 16 following a frozen embryo transfer. Tests on the baby identified no abnormalities. I had swabs taken when being treated at the hospital which identified bacterial vaginosis and e-coli. I had anti biotic treatment for this. As I am pregnant again I am terrified that I may have BV again and that this had some impact on my last miscarriage. I went to my GP yesterday and had swabs taken. I have been advised I may be prescribed metronidazole if BV is identified however I am very concerned about taking any medication, particularly in the first trimester. However I am also scared that if I do not have treatment I may be more susceptible to another miscarriage. What are current recommendations regarding antibiotics in pregnancy and BV in pregnancy. I have been using Balance Activ BV gel as it says it is safe in pregnancy. Would this be a safe and effective alternative to antibiotics?
      Thank you, Lesley

    • By Midwife @Tommys on 8 May 2017 - 16:18

      Thank you for your comment. Congratulations on your pregnancy and I hope everything goes well for you
      I understand your concerns about taking medication in pregnancy,
      "If BV develops in pregnancy, it may increase the risk of pregnancy-related complications, such as premature birth or miscarriage. However, this risk is small and appears more significant for women who have had these complications in a previous pregnancy. BV causes no problems in the vast majority of pregnancies.
      As a precaution, you should contact your GP if you're pregnant and you begin to have vaginal discharge (although discharge can be a normal part of pregnancy)."

      If you do have BV, I would advise that you consider taking Metronidazole if prescribed; medications are not usually prescribed in pregnancy unless there is a risk to your health if you do not take them so please be guided by your GP's advice

      As you are using a BV gel, please also be aware of the following facts to help you make a decision whether or not to take metronidazole
      "Vaginal pH correction treatments are a relatively new way of treating BV. These usually involve applying a gel to the inside of your vagina that changes the acid balance, making it a less hospitable environment for harmful bacteria. Most vaginal pH correction treatments are available over the counter from pharmacists.

      However, it's not clear how effective these treatments are for treating BV. Some studies have suggested they may help, whereas others suggest they're either ineffective or less effective than antibiotics"

      I have attached 2 links that have additional information that may help you!scenario:1

      Hope this helps
      Please contact us again or call our helpline for further advice
      0800 0147 800
      Take care
      Tommy's Midwife

    • By Anonymous (not verified) on 11 May 2017 - 10:58

      Thank you so much Marianne.

    • By Kerry (not verified) on 6 May 2017 - 16:46

      My last period was the 14 of march I took a pregnancy test an it came out positive .So my concern is how many week can I ne pregnant

    • By Midwife @Tommys on 8 May 2017 - 11:50

      Thank you for your query. As your last period was 14th march, you are currently 7 weeks and 6 days pregnant.
      I hope everything is going well and would encourage you to either contact your GP or local maternity unit so that you can start your pregnancy care. Make sure you are staying healthy-by having a healthy diet, following safe eating in pregnancy advice and taking folic acid supplements for pregnancy. I have attached some links that you may find helpful

      Please do not hesitate to contact us for further information or call our helpline 0800 0147 800

      Marianne-Tommy's Midwife

    • By Abosede ogunsola (not verified) on 10 Aug 2017 - 19:22

      my last periods was the 9 July

    • By Midwife @Tommys on 26 Apr 2017 - 09:38

      Hi please get back in contact if you need advice as your message is incomplete.
      Tommy's Midwives

    • By Janet (not verified) on 25 Apr 2017 - 09:04

      I had my last period on 25th March and unprotected sex on de 6th of April. I took post in or 2 after twelve ours . I've had a posi

    • By Anonymous (not verified) on 24 Apr 2017 - 10:44

      I m pregnant and uts my 6 week bt i m not having any splecial feeling like vomiting. Is it ok wid my pregnancy

    • By Midwife @Tommys on 24 Apr 2017 - 13:23

      Congratulations on your pregnancy.
      Every woman id different and experiences pregnancy differently. For some that means a lot of nausea and vomiting and for some none at all. Try not to worry - you may be one of the lucky ones to not get the nausea and vomiting, or you may find that as the pregnancy progresses you start to feel it.
      Enjoy your pregnancy and if you haven't already start taking Folic Acid and Vitamin D supplements as well as visiting your GP or midwife for antenatal care and advice.

    • By Anonymous (not verified) on 23 Apr 2017 - 10:22

      My depo provera wore off before my next injection was due , I had my period and was just wondering if there is any chance I could be pregnant , I've been feeling dizzy and feeling sick all day for the past week and I passed out once . I had my injection on the 18/4/17 , if I am pregnant can the injection harm the baby ??

    • By Midwife @Tommys on 24 Apr 2017 - 09:54

      Hi - thanks for your message.
      Its difficult to say if you are or aren't pregnant without a positive pregnancy test. Please visit your GP who can advise and maybe able to carry out a pregnancy test if you aren't able to - but also for the symptoms you have had too.
      If you would like to discuss in more detail please feel to contact us here at Tommy's Pregnancy Line on 08000147800 or via email [email protected]

    • By Brigitte (not verified) on 21 Apr 2017 - 20:03

      I took pregnant test 20th april and found im last period was many weeks my pregnancy is?..Also im very stressing because i have problem with sciatic pain/low back this will be the risk to my pregnancy?..

    • By Midwife @Tommys on 24 Apr 2017 - 09:49

      Hi, Congratulations on your pregnancy and also for finding our site which will help you over the next months.
      If the first day of your last period (your LMP) was on 15/03/2107 then you would around 5+5 weeks pregnant - depending on how long your cycle is.
      If you haven't already please start taking folic acid and vitamin d supplements and visit your GP for a check and to be referred for antenatal care.
      I'm sorry to hear you have sciatic/back pain - neither are a risk to your pregnancy but you may find that you may find the discomfort increasing - again visit your GP early for advice and support.
      Good luck for the coming months!

    • By Anonymous (not verified) on 20 Apr 2017 - 08:37

      Hey there :) i found out that i am pregnant obly yesterday and i am super exited for it. But today i am starting to have a bit of cramps and i am very scared about it i am nearly 7 weeks in (6 weeks 6 days).... i am so scared that i will loose my baby .. is it normal to have cramps or a little bit of pain?

    • By Midwife @Tommys on 20 Apr 2017 - 09:56

      Hi, Congratulations on your pregnancy and also for finding our site which will help you over the next months. It isn't uncommon to experience some mild period like pain which is usually attributed to implantation, or occasional sharp pain where the ligaments are stretching. If the symptoms don't resolve or if they get any worse please see your GP for advice.

    • By Hemamalini (not verified) on 16 Apr 2017 - 16:00

      Hi Good eve,
      I am 11 weeks now and no heart beat found when scanned. What should be done to bring the heart beat. I am so scared and under medication to induce heart beat. Till he many weeks I should wait and what is the maximum week ?

    • By Midwife @Tommys on 18 Apr 2017 - 09:51

      Hi there - I'm sorry to hear you have been told that there is difficulty in finding baby's heart activity during an early pregnancy scan. In order to advise I would need some more information and clarification of a few details - please contact us either via email [email protected] or on our Pregnancy Helpline 08000147800 so that we an offer confidential support and advice.

    • By Anonymous (not verified) on 10 Apr 2017 - 10:53

      Hi ! I am Pregnant and almost 8 weeks. Had issues with my partner because he said he isn't ready financially. I cried and stressed a lot during my 3-4 weeks period, could this have affected the baby in anyway?

    • By Midwife @Tommys on 10 Apr 2017 - 11:01

      Hi there. Congratulations on your pregnancy. And I am sorry to hear that you have had a difficult time with your partner recently too.
      Stress in pregnancy is very tough to deal with, but will not physically harm your baby's growth or well-being. I hope that you partner is being more supportive now and that you have a good friend and family support network too. Please do speak to your GP and Midwife about any ongoing anxiety during your pregnancy as they will be able to support you with more appointments as well as referrals for additional support should you want or need it. Asking for help is always a good thing to do if you are worried or concerned during pregnancy. Do also feel free to call us on our pregnancyline or email us privately on [email protected] We are not counselors, but midwives with a friendly ear, regardless of the situation. Please take good care of yourself.

    • By confused (not verified) on 8 Apr 2017 - 23:48

      Had intercourse with hubby on 26th january.i didn't see my period again till February ending and it has bin regular.could I really be pregnant because I think I am supposed to see the period before February ending.i have not really had any prenancy symptons..just confused...could I be pregnant?

    • By Midwife @Tommys on 10 Apr 2017 - 09:35

      Hi there. It is a little difficult to know. Have you done a pregnancy test at all?
      If you are not pregnant, then it would be sensible to go to your GP to get a referral to a gynae clinic to be reviewed. Sometimes, alterations on your menstrualy cycle pattern can be triggered by something else and so it is best to get it checked out if this is the case. Take good care of yourself

    • By scared (not verified) on 7 Apr 2017 - 15:32

      hi just dnt know wats going wit me ddnt see my periods for 3 months but testing neg I dd 4 test already n I have abdominal pains n sore breast, when I visited a clinic the nurse said I have infection then gave me some treatment but still no change could I be pregnant?

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