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13 weeks pregnant

Week 13 marks the start of the second trimester. You won’t wake up suddenly feeling blooming and back to your usual self but you should definitely start to feel a bit more human over the coming days and weeks. Trimester two is the good bit, when you’re over the early days of sickness and tiredness but not yet so big that your size and extra weight you’re carrying is taking its toll. Your baby is making a start on some new projects this week, too.

By Mumsnet HQ | Last updated Jul 15, 2021

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Your bump at 13 weeks

You may well have the beginnings of a bump around now and, depending on your general shape and size, your belly button could already have gone from being an ‘innie’ to an ‘outie’. If you were already the proud owner of an ‘outie’, you’ll probably just be more out and proud than ever. Either way, once your belly button pops out it stays that way for the rest of your pregnancy.

What size is your baby at 13 weeks?

At 13 weeks your baby is about 7.5cm long and weighs about 23g – about the size of a large egg.

How is your body changing at 13 weeks pregnant?

While you’re navel-gazing/marvelling at your emerging bump, you might also want to give some thought to your expanding rib cage. If you’re getting measured for a bra soon, you may well find that your back is bigger than before. This is because your rib cage has expanded at the bottom to cope with the increased volume of air your lungs are taking in.

Lots of women find their rib cage doesn’t ‘decompress’ again after your baby is born. It’s the same for feet, which often get bigger during pregnancy due to the extra weight being put on them. Many women remain a shoe size bigger for life.

In other slightly annoying news, you can say hello to heartburn and constipation around now. As progesterone and oestrogen slow your digestive system, it takes longer for food to exit your stomach, leaving you feeling like your meal is still sitting there hours later. The slowing-down process has a positive role to play, however, allowing the maximum amount of nutrients to be absorbed from your body to feed your baby, but it’s less fun for you (see below).

Your baby at 13 weeks

Your baby is looking more like a little human. His face is much more like the face you’ll meet in six months’ time and he’s starting to look a bit more in proportion.

  • This week, your baby’s skeleton starts to develop.The first bones to form are the clavicles (collar bones) and femurs (thigh bones) but soon more bones will develop in the arms and legs.
  • Your baby's face is looking much more like it should now. He can sometimes look as though he is making facial expressions – they are random movements rather than real expressions, obviously, but are still pretty amazing.
  • His eyes, which have been a bit to the side, now take up their rightful place at the front, so he can look you straight in the eye. Although closed, his eyes will be moving slowly under the eyelids.
  • He can open and close his mouth and stick out his tongue.
  • His ears are beginning to stand out a little on the side of his head, too.
  • It seems rather early, but your baby's hair pattern is sorted out at this time as well. So if he’s going to be cursed with a double crown, that’s already predestined now.
  • He is moving around quite a bit, kicking, flailing his arms and grasping with his hands. He can even suck his thumb now and you might spot him doing so on a scan – all practice for self-soothing after birth.
  • He has bursts of activity, stretching his legs and arms. His muscles are developing, as are the nerves that make them work, and it's thought this activity is practice for the outside world so that each group of baby muscles knows what it's meant to do when it grows up.
  • His skin is still thin and transparent enough to be able to see blood vessels in places. Your baby doesn't have any fat yet, so he looks sort of pink and skinny at this stage.
  • All the organs in your his body are continuing to grow.
  • The lungs are also getting bigger and he’s practising how to breathe. He doesn't need to breathe 'properly' in your womb because his blood largely bypasses the lungs and gets the oxygen it needs through the umbilical cord. But as soon as he's born, he'll need to breathe to get oxygen from the air around him – the umbilical cord and the placenta are history – so wisely, he has a gentle try-out before birth. Because he's surrounded by amniotic fluid, this means he's effectively breathing underwater.
  • His stomach and bowels are all growing bigger and, on the inside, the bowel is developing little finger-like projections called villi, which absorb important nutrients from the food we eat into the bloodstream.
  • And, appropriately we think, his vocal cords are developing this week, too. So, with lungs, vocal cords and intestines all underway, he’s getting in some early practice on screaming and pooing this week – all skills he’ll be using regularly in his first weeks of life.
  • Finally, your baby's heart has stormed ahead in development. If you hear his heartbeat (through a Doppler machine that your midwife or doctor uses) it can sound alarmingly fast – like a mad galloping pony. This is normal. Your baby's heartbeat is around twice as fast as your own.

Pregnancy symptoms in week 13

As you enter the second trimester some of the early pregnancy symptoms ease off. It may not happen immediately but you should find that the worst of the tiredness lifts and you can look forward to feeling more normal again.

Sickness easing

If you suffered with morning sickness you’ll find it won’t disappear immediately but you may find it's getting easier. Maybe you can now tolerate smells that, earlier on, were utterly stomach-turning.

If you find that you are still suffering, there are some ways to relieve the symptoms of morning sickness that many women swear by – although there's no miracle cure, we're afraid.


Those pesky hormones are at it again, slowing your digestive system and relaxing the valve that separates the stomach from the oesophagus, creating a perfect storm for acid to creep up into your throat.

Heartburn feels like a pain behind your sternum (breast bone) that is usually worse when you lie down. You can also get a nasty acidic taste in your mouth when the stomach’s digestive fluids rise up your oesophagus into your mouth.

Discuss this with your antenatal team as simple over-the-counter remedies can help, but there are safe, more effective medicines if you need them. By week 40 you may feel like your pregnancy is sponsored by Gaviscon.

Try to avoid spicy and fatty foods as these can make it worse, and don’t eat anything just before bedtime. Yoghurt and milk can soothe the discomfort a little, too. Heartburn is not, however, a sign that your baby is very hairy. This is a (slightly odd and disturbing) myth.

Things to think about during week 13 of pregnancy

A few things to pop on your ‘could do’ list for this week.

Announcing your pregnancy

If you haven't already, you might like to think about telling your loved ones your baby news. Don't feel obliged to tell them at this point if you don't want to, though – the longer you leave it, the less time there is for people to give you their very unwelcome well-meaning advice.

Maternity capsule wardrobe

If you’ve not bought anything yet, now might be an ideal time to invest in a few new items of clothing to see you and your expanding middle through the next six months.

You’re probably finding things are getting a little tight in the waistband, particularly after eating, so sorting out some maternity wear will make you more comfy. And trust us – once you’ve tried a pair of over-the-bump maternity jeans, you’ll want to wear them for life (or at least for roast dinners for the rest of your life).

Changes to your diet

As well as bearing in mind any foods to avoid in pregnancy, you could also think about any tweaks you can make to your diet to help you feel a bit better.

If big meals are sitting heavily on your tummy, try switching to having five small meals a day instead. If certain smells still make you feel a bit like retching into the bin, go for blander foods instead. A useful tip is that raw veg is a great way to ensure you’re getting your five a day if the smell of a boiled carrot still has you heaving.

What Mumsnetters say

"I was about one size bigger on the waist at 13 weeks, no different on the boobs but then they were pretty big to start with!"

"Everybody is different but at 13 weeks my waist had thickened up and I couldn't do up my jeans. My boobs looked great but weren't that much bigger. Just somehow…better."

"It's a weird stage. I haven't announced it publicly yet so I guess I feel less pregnant and more like a huge beast. I'll get used to it!"

"I wake up every morning with a blinding headache. I thought it might be my pillows, to begin with, but new ones didn't help. I spoke to my midwife last week and, after checking my blood pressure, she confirmed they were hormonal. She said paracetamol was safe, even if they don't do anything!"

What's next: 14 weeks pregnant