At 23 weeks pregnant, your baby is about 28.9 cm long, roughly the size of a papaya, and weighs about 1.1 lb (500 g). The lungs are growing quickly, although they are not yet ready to work outside the womb.

For you, this is often the week that breathing starts to feel different. You may be out of breath on the stairs, or sore under the ribs where your baby's feet are. This guide explains why, and how to tell normal breathlessness from a warning sign.

Your baby this week

Your baby's lungs are the main focus. The airways are branching like the limbs of a tree, and tiny air sacs are starting to form at the ends. Blood vessels are growing around them so that, after birth, oxygen can move from the air into the blood.

Your baby practises breathing by moving the chest and diaphragm, taking amniotic fluid in and out. The fluid, not air, fills the lungs at this stage, and your baby gets oxygen through the placenta. Some of the cells in the lungs are also beginning to make surfactant, a slippery substance that stops the air sacs from sticking together when a baby breathes. Production increases over the coming weeks.

How it happens. Lungs are one of the last organs to be ready for birth. Babies born extremely early can need help with breathing because they do not have enough surfactant yet. This is why providers sometimes give steroid injections to people at risk of early birth (see week 24).

Your body this week

Your uterus is now well above your belly button, and it presses up on your diaphragm, the muscle under the lungs. At the same time, progesterone makes you breathe faster and deeper, so your body takes in more oxygen for you and your baby. You may notice that you breathe more often, or feel out of breath when you did not before.

Your ribcage also widens a little, and the lower ribs flare outward to make room. This is normal, and it usually goes back after birth.

Common symptoms at 23 weeks

  • Feeling out of breath. It often happens when you climb stairs, walk quickly or talk while walking.
  • Kicks under your ribs. Your baby's feet may rest against the lower ribs.
  • Aching ribs or side. The ribcage is expanding, and the ligaments there are stretching.
  • Tiredness returning. Carrying more weight takes more energy.
  • Thicker, faster-growing hair and nails. Pregnancy hormones extend hair growth.
  • Strong movements. You may see your belly move when your baby kicks.

Is your breathlessness normal?

Mild breathlessness is common in pregnancy, affecting many people during the second and third trimesters. It tends to be gradual, comes with activity or lying flat, and eases with rest. You can usually talk in full sentences.

It is more likely to be a problem if:

  • It starts suddenly, or is severe.
  • You are breathless at rest, or when doing little.
  • You have chest pain, a racing heartbeat, or feel faint.
  • You cough up blood, or have a cough with fever.
  • You have wheeze, or your lips look blue.
  • You have pain, swelling or redness in one calf.

These can be signs of a blood clot in the lung, a heart problem, an infection or asthma that is not controlled. Get urgent medical help.

If you have asthma, keep taking your prescribed inhalers. Well-controlled asthma is safe in pregnancy, and untreated asthma is a bigger risk to your baby than the medicines. Tell your provider if your asthma changes.

Easing breathlessness and rib discomfort

  • Slow down. Pace yourself, and take breaks on stairs.
  • Sit and stand tall. Good posture gives your lungs more room. Slouching squashes them.
  • Raise your upper body when resting. Prop yourself with extra pillows in bed.
  • Stretch your arms overhead. This can lift the ribcage and ease pressure. Do it gently, and stop if it hurts.
  • Move your baby's feet. If a foot is jammed under your ribs, change position, or lie on your side and shift gently.
  • Wear loose clothing. Avoid tight bras and waistbands. Choose a bra with a wide, soft band.
  • Practise slow breathing. Breathe in through your nose, letting your ribs expand, and out through your mouth. It can calm you as well.
  • Stay active. Regular gentle exercise improves your lung capacity over time.

If rib pain is sharp, severe, or comes with fever, vomiting or pain under the right ribs, call your provider. Pain under the ribs on the right side can be a sign of pre-eclampsia, which is covered in week 25.

Your week 23 checklist

Call your provider

Call an emergency number if you are suddenly and severely breathless, have chest pain, cough up blood or your lips turn blue. Call your provider the same day for breathlessness that is getting worse, a wheeze, calf pain or swelling on one side, or a fever with cough. This guide is general information and does not replace medical advice.

Frequently asked questions

Is it normal to be short of breath at 23 weeks pregnant?

Mild breathlessness is common. Your uterus presses on your diaphragm, and progesterone makes you breathe faster. Sudden, severe or resting breathlessness is not normal.

Why do my ribs hurt during pregnancy?

The ribcage expands to make room for your growing uterus, and your baby may kick or press against the lower ribs. Changing position often helps.

When are a baby's lungs developed?

Lungs keep maturing until close to birth. Surfactant production starts over the coming weeks, and lungs are usually mature enough for breathing at full term.

Sources

Sources: NHS: 23 weeks pregnant; NHS: Common health problems in pregnancy; Mayo Clinic: Fetal development, the second trimester; Cleveland Clinic: Fetal development, week-by-week stages of pregnancy