13 weeks pregnant

You and your baby's development

What's happening in week 13 of your pregnancy

Week 13 is here, and you are probably sharing the news of your pregnancy with anyone who'll listen!

At a glance

  • Your little one is now about the size of a plum
  • Kidneys begin to function
  • Time to start looking for a capsule maternity wardrobe
13 Weeks pregnant

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How big is my baby at 13 weeks pregnant?

Your baby is around 7.4 cm long and about the size of a plum, weighing about 23g. Even at this small size they’ve already learned some party tricks – kicking their legs, turning their head – even swallowing, yawning and hiccupping. How amazing is it that they are so active and developed, yet so tiny?

In week 13, your baby’s skeleton is starting to develop with the clavicle (collar bone) and femur (thigh bone) developing first. Along with the skeleton, their organs continue to grow with their stomach and bowel taking shape as well as their vocal chords (which will get a lot of use in a few months' time!)

Your baby’s lungs are also developing and in week 13 they’ll start to take their first few ‘breaths’ via the umbilical cord. They’ll be getting oxygen in their blood from the umbilical cord as they’re surrounded by amniotic fluid, so instead it’ll be like they’re breathing under water.

At this stage, their kidneys are functioning and any amniotic fluid your baby swallows, they will wee out.

Did you know?

  • Your baby is around 7.4 cm long and about the size of a plum, weighing about 23g.

  • Babies can taste the food their mothers eat in the womb and this may even shape their preferences in later life.

  • Your baby's vocal chords are beginning to develop.

  • Your baby’s ovaries or testes have now formed in the body and the clitoris or penis is now forming externally where a bump was before.

  • At this stage of pregnancy your baby sleeps for a few minutes at a time, later in pregnancy they start to sleep for longer periods and you may recognise later on a routine to when you baby sleeps.

You at 13 weeks pregnant

You are probably feeling a lot more confident and secure in your pregnancy now you have reached the 13 week mark and your chances of miscarriage are greatly reduced. It is probably also something of a relief to be sharing your news with your wider circle of friends (although how many immediately said they'd already guessed?)

You should be feeling a lot better generally now as your placenta takes over the production of pregnancy hormones, which should ease any nausea. You might even feel you are taking on a bit of a pregnancy bloom as your enter your second trimester!

As your baby is growing in leaps and bounds, you are probably noticing your clothes feeling a bit more snug now. Seize the moment to have a shopping spree and build a capsule maternity wardrobe to take you through the next six months in style (you might feel less inclined to spend all day in the shops once your bump has further blossomed).

Weeks 13-28 represent the second trimester of your pregnancy, roughly speaking months 4, 5, and 6 – the middle of your pregnancy.

As your pregnancy begins to feel more ‘real’ you might start thinking ahead and wondering about finding out whether you’re having a boy or a girl at your next scan.

If you want to know your baby’s sex ask the sonographer at the start of the scan. Although, some hospitals have a policy of not telling parents the sex of their baby. 

If you would still like to find out, you might consider having a private scan. Remember it’s not an exact science. They get it right around 95% of the time, so there’s still a 5% chance of getting it wrong! If your baby’s lying in an awkward position or moving around a lot it may also be difficult for the sonographer to tell.

Facts to know about you in week 13

  • Some say heartburn means you are more likely to give birth to a baby with a full head of hair.
  • Because blood flow increases during pregnancy, occasional nosebleeds and bleeding gums are common.

What to think about in week 13 of pregnancy

You and your partner might be planning to treat yourselves to one last couple's holiday before your baby arrives – and now could be the time to get thinking about destinations, vaccinations and flying restrictions! Most airlines will have their own rules and regs regarding how late pregnant women can fly, and restrictions on long haul after a certain number of weeks. Make sure you take your pregnancy notes with you if you go away (even though many maternity units have electronic records now, women are still provided with some information which could be helpful if medical advice is needed at another unit).

It's good to bear temperatures in mind too if you are booking a last-hurrah break – you might not enjoy hot and sweaty tourist resorts with a burgeoning bump in quite the same way as you did in your pre-pregnant state!  

Now you’re past those crucial 12 weeks of pregnancy and cruising into your second trimester, it may be a good time to think about some gentle exercise. 

After all, enjoying some activity during your pregnancy can help to boost your health and can also benefit your unborn baby’s development too.

Especially if you are not used to exercising, a simple stroll is the perfect place to start.

During pregnancy your pelvic floor muscles loosen due to hormonal changes so doing pelvic floor exercises will help you control any accidents when you cough, laugh, sneeze or exercise - try stopping an imaginary wee rather than a real one then lift and tighten by imagining doing the following at the same time: 

  • Squeezing your bottom as if stopping a poo
  • squeezing to stop the flow of wee
  • squeeezing as though you're gripping a tampon in your vagina

Initially the excitement of finding out you're pregnant and going through sharing the exciting news with your friends and family can give you a buzz that boosts your relationship, but as things settle down, couples may find their usual energy as a couple lacking. It’s common for couples to find themselves arguing more than they did before. And it’s no wonder – you’ve got some pretty major change on the way. Arguing is perfectly normal – the most important thing to do is be sure you tackle the root cause of the issue and talk things over.

Don’t be afraid to ask for help if you need it, after all, you and your partner are in this together and it’s important to get to grips with working as a team now to help you get off to a great start when your baby arrives.

Signs and symptoms at 13 weeks pregnant

Higher sex drive

As you creep into your second trimester it’s not uncommon to feel an increase in your sex drive (but perfectly normal if you don’t). It might be the first time you’ve felt like sex in a while! Your energy in general will start to increase in your second trimester which can explain why your sex drive increases. Also, the increased levels of oestrogen and progesterone, (sex hormones) are responsible for the rising blood flow to the pelvic area and the amount of lubrication down there. It’s perfectly safe to enjoy a healthy sex life during your pregnancy, while you feel like it anyway!


Those pregnancy hormones can wreak havoc on your digestive system not to mention your growing uterus nicking some of the space your bowel usually takes up. If you have a low iron count in your pregnancy you may be prescribed iron tablets and these can cause constipation. If you experience this, speak to your GP or midwife and see if you can change to a different type. Although uncomfortable, there are a variety of things you can do to help including eating fibre rich foods and drinking plenty of water.

Video 1: Sex in pregnancy (From the NHS)

NHS Choices logo

Video 2: Pregnancy exercise

Video 3: How to eat and drink healthily in pregnancy

At a glance

  • Your little one is now about the size of a plum
  • Kidneys begin to function
  • Time to start looking for a capsule maternity wardrobe

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