Your baby is the size of a large plum

13 Weeks Pregnant: Your Baby's Development

As you hopefully start to regain at least some of your energy in the second trimester, your foetus is getting more and more active inside the uterus. You probably won't feel it until later in the second trimester, but your little one is dancing around a lot in there!

The arm and leg movements are random and jerky at first, but they'll be getting more and more deliberate now that you're 13 weeks pregnant. Some foetuses even suck their thumb in the uterus. If you're lucky enough to see this on a future ultrasound scan, you'll probably agree it's one of the cutest things you've ever seen!

Thumb sucking is not only cute, it's also beneficial. It helps your little one develop that all-important sucking reflex needed for feeding after birth.

The ovaries or testes are now fully formed inside the body of your growing foetus. Those tell-tale external genitals are starting to develop as well, although it's probably still too early for your doctor to tell the sex during an ultrasound scan.


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The Size of the Foetus at 13 Weeks Pregnant

At 13 weeks, your foetus is now about the size of a large plum, measuring close to 7.4 centimetres from crown to rump, and weighing approximately 25 grams.

It can be hard to imagine exactly what’s going on inside your belly. Check out the visual below to get an idea of how your little one is looking.

Baby at 13 weeks pregnant

Mum's Body at 13 Weeks Pregnant

Welcome to the second trimester! This trimester is often referred to as the ‘honeymoon period' of pregnancy. It may seem hard to believe, but you're already a third of a way through.

Some mums-to-be start to really ‘glow' around this time, and many regain some of their lost energy too. If you've been suffering from some common early pregnancy symptoms such as morning sickness, you might find these symptoms ease off in the weeks ahead.

Every pregnancy is different though, so don't be discouraged if you're still feeling a little off-colour.

Each mum-to-be and each pregnancy is unique, but you may also start to develop the beginnings of a bump at 13 weeks pregnant, as your uterus expands upwards and outwards to make room in your belly for your growing foetus.

As your uterus lifts away from your bladder, trips to the loo could also become less frequent.

Meanwhile, some mums-to-be experience an increase in their sex drive during this period. This could be due to the increased flow of blood around the pelvic area, or to pregnancy hormones.

It's usually safe to continue having sex during your pregnancy if you and your partner want, as long as you haven't been advised against it by your doctor or midwife.

13 Weeks Pregnant: Your Symptoms

Here are some of the symptoms you may be experiencing at 13 weeks pregnant:

  • Sore breasts. Your breasts may get bigger and feel tender, a bit like they might do just before you have your period. The veins may also become more visible, and your nipples could get darker and stand out more.

  • Stronger food cravings. If you had food cravings in your first trimester, they could be getting stronger now. These cravings can last right up until you reach the third trimester. You might get a sudden longing for fatty foods like burgers and chips, for odd combinations like chocolate and bacon, or for things that you hated until now. It's OK to give in to your cravings from time to time, but try not to get too carried away, and eat as healthily as you can. Let your doctor or midwife know if you're craving things you shouldn't be eating at all, like toothpaste, dirt, coal or soil. This could be a sign of an iron deficiency, which can be dangerous if left untreated.

  • Increased thirst. You might feel a bit thirstier than usual sometimes. This is natural, and can happen as your body produces extra blood to supply the growing area around your uterus. If, however, your thirst is constant and drinking more fluids doesn't make it better, talk to your doctor or midwife so they can rule out a more serious problem like diabetes or anaemia.

  • Lingering first trimester symptoms. You might find the symptoms of early pregnancy vanish completely when you're around 13 weeks pregnant, but there's a chance some of those early pregnancy symptoms, like bouts of nausea, headaches, fatigue and mood swings, linger for a while longer.

13 Weeks Pregnant: Things to Consider

  • Have you gone public with the happy news yet? Many mums-to-be choose to announce their pregnancy to friends and wider family at the start of the second trimester, when the risk of a miscarriage becomes much lower. If you're gearing up to share the news, check out these creative pregnancy announcement card ideas.

  • If you've been exercising to stay fit, keep it up, but don't overdo it! If not, know that gentle exercise during pregnancy is safe. In addition to helping you stay healthy and helping to keep your weight gain at a healthy level, it's also a great way of preparing your body for labour. Around 150 minutes of exercise a week brings loads of health benefits, even if you split this up into short, 10-minute sessions.

  • Walking, swimming and prenatal yoga are fantastic ways of keeping physically fit during your pregnancy, but you might also find aerobics classes that are specially geared to mums-to-be. Running is OK if you're already an experienced runner, but this might not be the time to take it up as a new sport. Always chat to your GP before taking up exercise during pregnancy. If you’re already exercising, it’s a good idea to let your GP know what you’re doing so he can confirm that it’s still safe now that you’re in the second trimester.

  • Avoid martial arts and sports like football, tennis or squash, which could risk your bump being knocked. Activities that could lead to a fall or throw you off balance, like horse riding, skating or gymnastics, are also best avoided. It's best to skip any that involve lying flat on your back for more than a few minutes. In this position, the weight from your uterus can cause less blood to return to your heart, causing dizziness or low blood pressure.

  • Pelvic floor exercises are really beneficial during pregnancy. These exercises help strengthen muscles that are important for pregnancy and labour, and they can also lower your risk of incontinence after giving birth.

  • If you're pregnant during the winter, your doctor may recommend you take extra doses of vitamin D, to make up for the lack of sunshine. You may also be entitled to free vitamins, ask your doctor about this at your next prenatal visit.

  • You might like to start putting together a pregnancy and baby budget, but it can be hard to know what to budget for. Start with doing some research by asking other parents with young children what baby gear they definitely recommend getting, and what you can easily go without. You might be able to borrow some items, get clothes second hand, or get recommendations on where to look for bargains on must-have items. For even more tips, check out our article on ideas to help you save.

13 Weeks Pregnant: Ask Your Doctor

  • Why do you sometimes get stomach pains or cramps?

  • What kind of prenatal supplements should you be taking?

  • What exercises are safe for you to do during pregnancy?

  • What genetic testing is recommended? And what are the risks and benefits?

13 Weeks Pregnant: Your Checklist

  • Make an appointment for a whooping cough vaccination. This vaccine is strongly advised for mums-to-be between 16 and 32 weeks of pregnancy. Babies who are too little to be vaccinated are at the highest risk of getting whooping cough. You getting this jab during your pregnancy gives your little one protection against whooping cough from the day he’s born.

  • Apply for a maternity exemption certificate if you haven’t already got one. This entitles you to free NHS dental treatment and free prescriptions while you’re pregnant, and for the first 12 months after giving birth. The application form is available from your doctor or midwife, who also needs to sign it.

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How we wrote this article
The information in this article is based on the expert advice found in trusted medical and government sources, such as the National Health Service (NHS). The content on this page should not replace professional medical advice. Always consult medical professionals for full diagnosis and treatment.