Pregnancy Week 23: Swimming, Exercise and Your Baby's Viability

Quick answer: At 23 weeks your baby is about 28.9cm and 500 grams, and from this week a baby born prematurely has a chance of survival with specialist neonatal care. Swimming is one of the best pregnancy exercises: the water supports your bump and eases joint pressure. Avoid diving, hot tubs, steam rooms and saunas, and tell your midwife about any breathlessness or change in movements.

What parents need to know

Week 23 marks a significant, if bittersweet, medical milestone: from this week, a baby born prematurely has a chance of survival with specialist neonatal care. Of course, the goal is for your pregnancy to continue as long as possible — but this is a reminder of how remarkable your baby's development has been over these weeks.

How big is your baby at 23 weeks?

Your baby is now about the size of a large mango — approximately 28.9cm from crown to heel and weighing around 500 grams. Half a kilogram of human life, fully formed and increasingly capable.

What's happening with your baby?

Your baby's lungs are developing rapidly, producing a substance called surfactant, which keeps the air sacs open so the lungs can function after birth. This is one of the key developments happening from around 23 weeks, though the lungs won't be fully mature until much later in pregnancy. Your baby now has regular sleep-wake cycles and may be making distinct movements — kicks, rolls, and stretches — that you can feel from the outside of your bump.

Your baby's sense of balance is developing, facilitated by the vestibular system in the inner ear. Their skin is becoming less transparent as more fat builds up beneath it, though it is still quite wrinkled at this stage. Your baby's hands are fully formed and increasingly active.

The benefits of swimming in pregnancy

Swimming is widely regarded as one of the best forms of exercise during pregnancy, and for good reason. The buoyancy of the water supports your growing bump, relieving the pressure on your joints and spine that becomes more pronounced on land. It's a low-impact, full-body workout that can be continued safely throughout all three trimesters (unless your midwife has advised otherwise).

Benefits of swimming during pregnancy include reduced back pain and pelvic girdle pain thanks to the supportive nature of water, improved cardiovascular fitness and stamina for labour, reduced swelling in the legs and ankles, better sleep (many women report improved sleep quality after swimming), and a positive effect on mood and anxiety levels. Aquanatal classes — antenatal exercise classes specifically designed for pregnant women and held in swimming pools — are available at many leisure centres across the UK and are an excellent option.

You don't need to be an experienced swimmer to benefit. Gentle breaststroke, walking in the water, or participating in an aquanatal class are all worthwhile. Avoid diving or jumping into the pool, and don't use hot tubs, steam rooms, or saunas, which can raise your core temperature dangerously.

What's happening in your body?

At 23 weeks, many women notice that their bump has become quite substantial and that physical discomforts are increasing. Breathlessness can occur as the growing uterus begins to push against the diaphragm. This is normal, but speak to your midwife if breathlessness is sudden, severe, or accompanied by chest pain. Haemorrhoids (piles) are another common pregnancy complaint, caused by increased blood flow and pressure from the uterus. A high-fibre diet, plenty of fluids, and regular movement can help prevent constipation, which worsens haemorrhoids. Over-the-counter creams such as Anusol are generally safe in pregnancy, but check with your pharmacist or GP.

Your week 23 checklist

This week:

• Try a swim or look for aquanatal classes near you.
• Maintain a high-fibre diet to prevent constipation and haemorrhoids.
• Mention any breathlessness to your midwife.
• Continue daily pelvic floor exercises.
• Keep an eye on your baby's movements — contact your midwife if you notice any change in their usual pattern.

Frequently asked questions

Is swimming safe in pregnancy?

Yes. Swimming is a low-impact, full-body workout that can be continued safely throughout all three trimesters, unless your midwife has advised otherwise. Avoid diving or jumping in, and don't use hot tubs, steam rooms or saunas.

Why am I breathless at 23 weeks pregnant?

Breathlessness can occur as the growing uterus begins to push against the diaphragm. This is normal, but speak to your midwife if breathlessness is sudden, severe, or accompanied by chest pain.

What can I use for piles in pregnancy?

A high-fibre diet, plenty of fluids and regular movement help prevent the constipation that worsens haemorrhoids. Over-the-counter creams such as Anusol are generally safe in pregnancy, but check with your pharmacist or GP.