12 weeks pregnant
Week 12 of pregnancy is the first big milestone. It’s the end of the first trimester, the chances of miscarriage fall off sharply at this point and, most excitingly of all, this is the week you’re likely to see your baby for the first time at your 12-week scan. And – we don’t want to worry you – but if you haven't been scanned until this point, you never know, it could be twins.
By Mumsnet HQ | Last updated Jul 15, 2021
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The 12-week scan
It's the moment you've been waiting for. However, the term '12-week scan' is a bit of a misnomer, since it could be scheduled any time between 10 and 13 weeks. You'll be given an ultrasound appointment at hospital which will usually take about half an hour – provided your baby is playing ball, that is.
During the scan, you'll be given an estimation of your due date; confirmation that there are no visible abnormalities and that development is happening as it should, and the, err, number of babies in there. What's more, most sonographers will give you a long-awaited picture to take home with you, too.
Your baby at 12 weeks
If you've got your scan this week you’ll get to clap eyes on your baby for the first time and suddenly all that information about how she's growing and developing becomes real.
You will probably get to see her heart, skull, spine and limbs on the scan and if she’s awake you’ll be able to watch her jumping about.
At 12 weeks, she can move her legs and arms individually as she's developing the sorts of muscles we use to walk and run with. It’s a little-known fact that, under the microscope, these muscles would look stripy.
Her head is still big in comparison to her body but her neck is getting stronger so she's able to support it more easily now. She’s also already developing unique facial characteristics. Scans are really quite difficult to see, however, so if she seems to have a boxer’s nose, jug-handle ears and a Desperate Dan jaw, she probably won’t have them when she’s born (unless your partner is Desperate Dan, of course).
Here's what else she's up to in there this week:
- Her eyes are still a bit far apart but are moving slowly closer together. Her ears are almost complete, however, including the inner and middle parts.
- She’s growing a fine layer of fuzzy peach hair called lanugo, which covers most of her body and will only be shed towards the end of the pregnancy. This helps her stay warm in the womb.
- Her bones are developing, with the middle bits of the cartilage scaffold she has been putting up now laying down calcium and becoming hard. Bones continue this ossification process until adolescence. At birth she’ll have 300 bones, which will eventually fuse into just 206 by adulthood.
- Her chest muscles are strong enough for her to start practising breathing – this is a long-term project that she’ll continue to hone over the coming weeks and months.
- She’s growing finger and toe nail beds. Awww.
- The intestines that she parked temporarily in the umbilical cord return back inside her abdominal wall, where they will remain now.
- Her liver and kidneys are working and she has a bladder to store the urine she's made when she starts swallowing amniotic fluid.
- Her liver is producing red blood cells and bone marrow is making white blood cells..
- Your placenta is nearly or already complete but will continue to grow along with your baby, providing her with food and oxygen and getting rid of her waste through the umbilical cord.
- Her heart is more fully formed and will start slowing down now to a more leisurely 110-160 beats a minute.
12 weeks pregnant symptoms
As things start to take shape and the uterus rises up out of the pelvis – you'll actually be able to feel it and may find you soon have a small bump, unless this isn’t your first baby, in which case you might already be showing.
The uterus making its escape from the pelvis means you'll get twinges of discomfort as it strains for freedom from the ligaments that are holding it to your abdominal wall. This is known as round ligament pain.
The ligaments will win but you may feel some slightly sharp or crampy pains in both sides of the lower abdomen when it happens. It’s obviously one of the more concerning symptoms of pregnancy but be assured it’s just your body getting on with its job.
Try to avoid making sudden movements, particularly when standing up from sitting or lying down. If the pain is more than just discomfort, gets worse rather than coming and going occasionally, or you experience bleeding with it, you should call your midwife team. If you find it gets worse when you're exercising, rest and reduce the pace or intensity.
Your 12-week bump
If this isn't your first pregnancy, chances are you're well on your way to having a proper little bump. However, if you're having your first baby, your abdominal muscles are probably stronger, so don't worry if it's still on the smaller side at this stage.
What size is your baby at 12 weeks?
The size of your baby at 12 weeks is about that of a small plum – or around 5.4cm.
How is your body changing at 12 weeks pregnant?
Your body is already starting to feel a little ‘out of the ordinary’.
The baby, placenta and fluid in total weigh about 2lb. It may not sound much, especially when you think that by the last trimester you’ll be thwacking on a pound a week, but you’ll be feeling the difference already.
If this isn't your first baby your abdomen is likely to think: ‘I've done this before’ and spring out suddenly in the manner of a puffer fish. Unless you've done some serious abdominal workouts since your last pregnancy, you're doomed to look close to term by the end of 12 weeks or, at best, find you can't fit into your jeans any more.
Things to think about during week 12 of pregnancy
Screening and diagnostic tests
As well as a dating scan, you should be offered a screening test for Down's syndrome and other genetic conditions at around this time. It's called a combined test because you have a blood test that measures specific proteins in your blood and a scan to measure the amount of fluid in the back of your baby's neck. This is called the nuchal scan and it’s often done as part of your dating scan so you don’t have to come in twice.
They combine the results of the blood test and scan and give you the result expressed as a risk factor, eg 1 in 500. The test is not perfect – it is a screening test not a diagnostic test – so will miss some babies with Down's syndrome.
If your results are considered high-risk, you will be offered an amniocentesis in which a small needle collects a sample of amniotic fluid through your abdomen and it’s sent off to a lab for testing.
Alternatively, you may be offered chorionic villus sampling, which is similar but instead takes a sample of the chorionic villi which attach the placenta to the uterus wall. Either will give you an almost 100% definitive diagnosis. However, both tests have risks attached.
There is a new test called NIPT, which stands for Non-Invasive Prenatal Testing, and is a screening test that has around 99% accuracy but no risk to the baby. It’s available privately at the moment.
Once the scan is out the way you’ll probably be dying to announce your pregnancy to your nearest and dearest. You may be surprised at some of their reactions. Some people will immediately say ‘Congratulations’ – but you may hear odd responses such as ‘I can't see you as a mum’ or ‘Was it planned?’ and other unhelpful comments.
Try to remember that people may have reasons of their own for a slightly unexpected response – perhaps they’ve been trying for a baby with no success. It can be hard to tell someone whom you know will be upset. If you’re worried, perhaps think about telling them on their own rather than in a group or drop them a text first so they can take the news in privately.
Of course, there are others who simply have foot in mouth syndrome and are best just ignored.
You also need to decide when to tell your employer. You're not obliged to tell them until 15 weeks before your baby is due. You can work out when this is according to your due date, going to the Sunday before it in your calendar and then counting back 15 weeks.
Most women decide to tell their employer before this stage. Once your employer has been informed they are obliged to ensure that you and your baby are safe at work by carrying out any necessary health and safety checks and making changes to your work if needed.
Also, you can't really start marking off your countdown to maternity leave in a big red pen on the wall of the office until they’re informed. It might look pointed.