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.


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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 Denise (not verified) on 25 Jan 2020 - 02:22

      I had cramping yesterday on my lower right side near my pelvis bone. Then earlier today I tinkled, wiped myself to find light reddish pink blood and few hours later it was gone. My underwear wasn't even stained. I have been nausea randomly as of late.

    • By Josephine Pikwo (not verified) on 21 Jan 2020 - 20:50

      I last had my period on 27th December 2019,,, I was supposed to receive a nother one on 15th January but I haven't received,,,yet I feel alot of dizziness, headache and morning sickness,,,am I pregnant or not?

    • By Sharee (not verified) on 31 Jan 2020 - 02:36

      Your time frame is the exact time from of my last period and when my cycle was supposed to start and I am now 5 weeks pregnant.. I had signs of light tender breast and nausea alot..

    • By Victoria (not verified) on 7 Jan 2020 - 00:25

      I was having some birth control pills for my period to cum monthly I start in Sept 2019 and finish Oct 3 then I start to bleed the 7 of Oct for only 4-5 days then I had unprotected sex the 12... Nov I begin to bleed again but lightly brown for couple days and I had unprotected sex often... Then December the 1st 2019 I start to bleed heavily for 6-7 days so I start to worried.. I got symptoms like feel sick.. like neausea, vomiting, pee more often like anytime I want to pee it coming down by it self quickly, having back pain, breast tenderness, heartbrun, face swell, feet and hand... Now its jan my cheast pain a lot i tired, feeling lazy and me and my partner cant gree at t'ime which is i cuss him and hare him im very moody... Can Simeone help me plz ecen thou my story very Kong

    • By Brittany Herbert (not verified) on 29 Dec 2019 - 23:37

      My last day of sex was December 4th. Three days prior to this I had pregnancy symptoms on the 6 I had a 4 day light period still have a few symptoms then on the 18tb I spotted for one day still had abdominal cramps and back pain I took 3 pregnancy all negative is there still a chance I’m pregnant??

    • By Maria patrick (not verified) on 24 Dec 2019 - 17:48

      i had my period on 29 of november. and i had sex with my husband on 11 of December. now i'm having pregnancy symptomes which i took pregnancy home test. but it came out nagetive. i'm confused. pls i need help.

    • By Amy (not verified) on 16 Jan 2020 - 13:36

      I took 3 pregnancy tests and they showed negative than I spotted for one day took a test 2 days after and came out positive

    • By Carol (not verified) on 22 Jan 2020 - 09:41

      I wnt something

    • By Lynn (not verified) on 29 Jan 2020 - 17:31

      I'm no professional, I can't tell you if you're pregnant. What I can tell you is that false negatives are common. Take at least four tests. Even if they all come out negative, the pregnancy may not be detectable yet. Best thing to do is go to a doctor and get a sonogram

    • By kira (not verified) on 13 Nov 2019 - 08:32

      I got my period last month but not this month, i mean at least not yet. I been experiencing pregnancy symptoms like being nausea & moody here and there. I got nauseous when i smelt the smoke of smoke and having cramps, peeing more than usual and being very sleepy also eating a lot.

    • By April (not verified) on 26 Dec 2019 - 22:06

      These were my exact symptoms. Yes, I found out a week later that I’m pregnant

    • By Suzan (not verified) on 2 Oct 2019 - 17:26

      Im 42 years On December last year while I was 5 weeks pregnant then I started to bleed, went to hospital doc took some lab blood to check hcg only to find Iit was ectopic. Last period july now im 9 weeks one day iam woried no symptoms at all, i took my home test 3 days before my period was positive even today still positive, I'm scared it should be ectopic again I'm afraid even to go hospital to be dissapoited, pls help me

    • By K (not verified) on 29 Oct 2019 - 09:32

      The best thing to do for you and your baby is to go see your doctor. I know you're scared, but it's the best thing you can do for both of you.

    • By Keisha (not verified) on 25 Sep 2019 - 10:13

      I had sex with my husband the 6 of August 2019 and my period came that same day then my period came back on the on the 1th of September and lasted 3 day but its was Brownish. My breast has been swollen and I am weeing more often than I am use to and I feel sick most of the time. I done a test early in august and it was negative so I dont understand if this is harmone or I am pregnant

    • By Anonymous (not verified) on 22 Sep 2019 - 18:28

      Am confused

    • By Radhika (not verified) on 22 Sep 2019 - 06:04

      I’m kind a scare that my first baby pass away on due date and it’s been 10month. I found out I’m pregnant again and I’m so scare, would that be possible if the first die and second will have problems? Should I ask anything to my OBGYN ???please advice!!!!

    • By Anna (not verified) on 8 Oct 2019 - 01:07

      Hi hun this happend to me and i fell pregnant a few months after and it my baby was fine so try not to worry to much just try to enjoy your pregnancy hope all goes well for you

    • By Smith (not verified) on 15 Sep 2019 - 23:01

      Hi my name is smith I jjust want to know if I use heroine and my wife won’t even smoke is there any problem with pregnancy?

    • By Arya (not verified) on 5 Dec 2019 - 13:15

      Please don't.

    • By vic (not verified) on 23 Dec 2019 - 01:09

      are you serious

    • By Risha (not verified) on 4 Sep 2019 - 09:13

      So i missed my periods last month and i took the test when i got my periods for the next month. The test showed negative but that still doesn't explain the missed period. What should i do?

    • By Ms Goode (not verified) on 6 Sep 2019 - 23:22

      The same thing happened to me. I went to my doctor and took a blood and urine test.... it came back positive. Check with you regular doctor

    • By Sherica Scott (not verified) on 17 Sep 2019 - 03:34

      I would encourage you to see a doctor it could be a sign of pcos, I have the condition and in some causes it cause miss periods.

    • By Katherine (not verified) on 29 Aug 2019 - 05:58

      Okay so last week my boyfriend and I had unprotected sex it was Friday the 9th and I have been having symptoms. Like I just got off my period the day before but now I am very sleepy in the morning and I've been peeing more and more I also can't really lay on my back because it hurts. and I had stomach pain and headaches I've not to be I've been blotted I haven't vomited but I've been nausea and dizzy are these signs of pregnancy.

    • By Anonymous (not verified) on 5 Sep 2019 - 07:52

      It seems you have got pregnancy you have early symptoms of pregnancy. For

    • By Zella (not verified) on 11 Sep 2019 - 12:18

      S of course. U might be if u haven’t experienced any of these symptoms earlier before getting your periods

    • By Lisa (not verified) on 26 Jan 2020 - 18:04

      If you have unprotected sex 3 days after your period, more than likely you will get pregnant

    • By Lungile (not verified) on 9 Aug 2019 - 03:41

      Hi I'm a woman of 34 my questions is yesterday I went to the local clinic for check up.I'm so confused and stressed at the same time course my due date is 12 of August so they said to me I must go to the hospital to get the abortion pill to make me deliver the baby so first how dangerous it is course I never done that in my in tiyer life I'm so scared.please help me.

    • By Mom of 2 (not verified) on 15 Aug 2019 - 03:25

      I would not recommend getting the abortion pill to make the baby deliver. Your baby knows when it needs to be born. The due date is just an estimate to make you aware that baby will be coming around that time. I would wait a little while longer (if you have not already had baby).

    • By Anonymous (not verified) on 6 Aug 2019 - 20:43

      I did not receive my next contraceptive injection when it was due,my husband and i decided to try for a second child, my injection was due 10 june,since then weve been trying maybe every second night, ive started feeling tired and started getting heartburn as well, there is some nuasia but not much,is it to soon to take a pregnancy test,i must add while on the injection those last weeks before the next one i was on antibiotics aswell

    • By Stephanie (not verified) on 30 Jul 2019 - 12:33

      I got my period last month but this month i only bled for 2 days straight which is unusual and light since then I've had sore breasts, heartburn and very strong backpains could I be pregnant

    • By Tom (not verified) on 6 Aug 2019 - 11:23

      What you experienced most probably is called implantation bleeding. the signs are of it. Do a home pregnancy test

    • By Lizzy (not verified) on 29 Jul 2019 - 11:52

      I took my last period on the 20th of June so with calculations midwifes think Iam 5 weeks but my stomach is massive Iook about 12 weeks what could this be

    • By Anonymous (not verified) on 28 Jul 2019 - 20:25

      I am pregnant,

    • By Nadia (not verified) on 16 Jun 2019 - 11:23

      My last period were on 6th may got a positive result i have a bad pain on my left always feel like there is something on my left side

    • By Sarah Barnes (not verified) on 10 Jun 2019 - 21:49

      Is it too soon to have sex after having a 10week old baby?

    • By Mallory (not verified) on 27 Jun 2019 - 02:54

      I believe usually healthcare providers advise to wait 4-6 weeks after delivery but you should probably double check with your own dr to verify all is well down there

    • By chantel (not verified) on 9 Jun 2019 - 00:28

      l last saw my period mid feb 2019 and had unprotected sex late feb to early march.Since february l havent had my period yet .my belly is slightly bigger and breasts without any other signs of being pregnant.l have not taken any test.can l be pregnant considering that my cycle is not stable at one time l went for 4 months without my period but l was not pregnant.

    • By Tracy (not verified) on 6 Jun 2019 - 07:05

      Hey im 18 years old . My last period was on may 4th , I was supposed to get my period on june 1st instead i have brown discharge for 6 days i took a pregancy test today and it came out negative but now im having pain around my ovaries can someone help mee

    • By Anonymous (not verified) on 7 Jun 2019 - 11:10

      I would contact an OB for hcg levels if you are pregnant. I mean you should regardless especially if you have pain. But typical Implantation bleeding only last a day or so

    • By Denis mugagga S... (not verified) on 15 Jun 2019 - 20:18

      Sorry about that dear u need to see a gynaecologist coz u could be having STIs

    • By Jc (not verified) on 18 Jun 2019 - 08:58

      Hey the exact same thing happened to me and I’m still waiting for my period, how did you turn out??

    • By Marcia (not verified) on 21 Jun 2019 - 14:31

      The brown Discharge you mentioned could be implantation bleeding. Since you posted this well over a week ago, you should take another pregnancy test if you haven't had your period yet. The pregnancy hormone often isn't detectible until after your missed period- so it would be wise to check again.

    • By Victoria (not verified) on 4 Jun 2019 - 23:05

      Hi. I had my 1st sex ever(un-protected) on the 6th of may(the week am suppose to have my period) so i did'nt see my period untill 24th of may. A week after i'd been feeling dizzy,having severe headache and sleepy every morning. But it only lasted a week. Have done a home test but it's not giving results. Could i be pregnant? Cause my Guy did'nt realease on me.

    • By Anonymous (not verified) on 7 Jun 2019 - 11:14

      If you got your period the 24th of May there’s really not a way you went through your mensural cycle, Ovulated, conceived and then implanted in that short of a time. Can’t do much if the tests are coming back negative too and that he didn’t inside of you.

    • By Orrelia (not verified) on 4 Jun 2019 - 08:43

      I have the worst morning sickness ever cannot keep fluids down for the past two to three days i have not been drinking any fluids and i have stomach cramps,headeaches and dizziness, i feel tired and i dont want to eat although i feel hungry because i vomit. I peeone or twice a day if i am lucky is this normal or should i be worried.

    • By Marie101 (not verified) on 3 Jun 2019 - 18:34

      Am I supposed to have pelvic pain first trimester?

    • By dennisonbritany... (not verified) on 27 May 2019 - 02:08

      I have heavy irregular periods issues and on birth control implant and missed 2 birth control pills from three weeks ago and missed 2 birth control pills two weeks ago and had sex last May 16 2019 few hours after stopped period then after had sex went in bathroom and wiped my private area and found just very tiny drop bleed then an hour stopped and don't have period anymore after that since, I took home pregnant test last week on May 19 2019 and came out negative, I still feel tiredness, have those headaches, weakness, cramps for two days, yesterday and today. And my private area is smell odd because it smell different, have morning sick every night, have nauseaous. And have been moody swing. one min grouchy, then laughing, then annoyed by others. And haven't have any period yet. So, am I possible pregnant? And my birth control implant is bended. Because it have been pains in my right upper arm where my birth control implant in.

    • By Gaga (not verified) on 25 May 2019 - 11:07

      I am 7 weeks pregnant. But, from 2 today, i have discharge with mixed blood when i wipe with toilet paper. I am very much worried

    • By Sarah (not verified) on 23 May 2019 - 11:53

      I am just over 4 weeks pregnant I have had some bleeding and cramping last night but this morning there isn't blood it's just a brown colour with some cramping, what does this mean

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