Pregnancy Week 29: Managing Back Pain and Your Baby's Busy Movements

8 min read

Quick answer: At 29 weeks your baby measures about 38.6cm and weighs around 1.15kg, with stronger, more purposeful kicks. Back pain affects up to 50% of pregnant women now, eased by low-impact exercise, good posture, side-sleeping with a pillow between the knees and supportive flat shoes. Contact your GP or midwife urgently about back pain, as it could be a sign of early labour, and call your maternity unit immediately about sudden swelling, a severe headache or vision problems.

What parents need to know

Week 29 brings increasing activity from your baby as they settle into more regular patterns of movement. You may also be finding that some of the physical discomforts of the third trimester are becoming more noticeable. Back pain in particular is very common at this stage, and there are practical steps you can take to manage it.

Baby's length	About 38.6cm crown to heel
Baby's weight	Around 1.15kg, like a small butternut squash
Back pain	Affects up to 50% of pregnant women
Swelling	Mild oedema common in third trimester

How big is your baby at 29 weeks?

Your baby now measures approximately 38.6cm from crown to heel and weighs around 1.15 kilograms, roughly the weight of a small butternut squash. They're growing quickly and will continue to put on weight steadily over the coming weeks.

What's happening with your baby?

Your baby's muscles and lungs are continuing to mature. They are actively practising breathing by inhaling and exhaling amniotic fluid, which helps the lungs develop the strength and coordination they'll need for breathing air after birth. Your baby's bone marrow is now fully responsible for producing red blood cells. The head is also growing to accommodate the rapidly developing brain. Your baby's kicks, punches, and rolls may feel stronger and more purposeful this week as their muscles grow stronger.

Managing back pain in pregnancy

Back pain affects up to 50% of pregnant women and is one of the most common complaints of the third trimester. It occurs because the growing uterus shifts your centre of gravity forwards, causing you to lean back to compensate and putting strain on the lower back. The hormone relaxin also loosens the ligaments and joints throughout the body, including those in the spine, which can lead to instability and pain.

Practical strategies to help manage back pain include: keeping active with low-impact exercise such as swimming, walking, or antenatal yoga; avoiding standing for long periods and taking regular breaks; using good posture when sitting — a small cushion or rolled towel behind the lower back can help; sleeping on your side with a pillow between your knees; wearing flat, supportive shoes; and lifting carefully by bending at the knees rather than the waist. Do not lie flat on your back for long periods, particularly after 16 weeks, because the weight of your bump presses on the main blood vessel bringing blood back to your heart, and this can make you feel faint.

Your midwife can refer you to a physiotherapist if your back pain is severe or affecting your daily life. A physiotherapist can provide targeted exercises and treatments to help. Some women also find that a maternity support belt helps reduce discomfort by supporting the bump and taking some of the strain off the lower back.

What's happening in your body?

You may notice that your ankles and feet are swelling, particularly towards the end of the day. Mild swelling (oedema) is very common in the third trimester. Elevating your legs when possible, staying hydrated, and gentle walking can help. However, sudden or severe swelling of the face, hands, or feet can be a sign of pre-eclampsia — contact your midwife immediately if this occurs, especially if accompanied by headaches, visual disturbances, or pain below the ribs.

When to get help

Some symptoms in pregnancy can be a sign of something serious and need checking quickly. This is who to contact, and how soon.

Call 999 if:

you're bleeding from your vagina and the bleeding is heavy (soaking a period pad soon after putting it on), or you also have severe pain in your tummy, pain in your shoulder, or feel sick, faint, dizzy or lose consciousness
you think your baby is coming now and you have a strong urge to push (ask for an ambulance)
you have severe difficulty breathing (you're gasping, choking or not able to get words out) or your chest feels tight or heavy
you have pain and swelling in one leg and you also feel short of breath or have chest pain. A blood clot in the leg can travel to your lungs, which can be life-threatening
you have possible signs of sepsis, such as breathing very fast, being confused or having slurred speech, blue, pale or blotchy skin, a rash that does not fade when you press it, or a very high or very low temperature. Being pregnant makes sepsis more likely
you do not feel you can keep yourself safe (a mental health emergency is as serious as a physical one)

Always call 999 if you think it's a life-threatening emergency, no matter what stage of pregnancy you are.

Call your midwife or maternity unit now if:

your baby is moving less than usual, you cannot feel your baby moving anymore, or there is a change to your baby's usual pattern of movements
you have light bleeding or spotting, even if you have no pain or only mild tummy pain
you have stomach pain that is severe or does not go away after you've rested for 30 to 60 minutes, or stomach pain with regular cramping or tightenings, lower back pain, or pain when you pee
you're less than 37 weeks pregnant and you have a gush or trickle of fluid from your vagina (this could be your waters breaking), regular contractions or tightenings, period-type pains, or backache that's not usual for you
your waters break, even if labour has not started
you have signs of pre-eclampsia: a severe headache that does not go away with simple painkillers, vision problems (such as blurred vision or seeing flashing lights), pain below the ribs, sudden swelling of the face, hands or feet, feeling very unwell, heartburn that does not go away with heartburn medicines, or being sick (vomiting)
your skin is very itchy (for example, it keeps you awake at night), the palms of your hands or soles of your feet are itchy, or the itching is worse at night. This can be a sign of a liver condition called intrahepatic cholestasis of pregnancy (ICP) that needs urgent treatment
your breathlessness comes on suddenly, you're out of breath when you're lying down, or you're breathless and also have chest pain or feel dizzy
you have pain or swelling in one leg, usually in the calf or thigh. This could be a blood clot (deep vein thrombosis, or DVT), which is more likely when you're pregnant
you have a high temperature (38C or above), or you feel hotter than usual or shivery. A high temperature can be a sign of an infection, so it's important to get it checked

If your baby's movements change, do not wait until the next day: call immediately, even if it's the middle of the night. Do not use a home doppler to check the heartbeat yourself. Even if you hear a heartbeat, this does not mean your baby is well.

If you cannot reach them, or you're not sure what to do, call NHS 111.

Contact your GP or midwife urgently if you have back pain and you:

are in your second or third trimester, as this could be a sign of early labour
also have a fever, bleeding from your vagina or pain when you pee
have pain in one or more of your sides (under your ribs)

Call 999 or go to A&E if you have back pain and you lose feeling in one or both of your legs, your bum, or your genitals.

Speak to your midwife or GP if:

you're worried about your mental health, or stress, anxiety or low mood are affecting your day-to-day life. If you need urgent help for your mental health, call 111 and select the mental health option, or ask for an urgent GP appointment

Go to sleep on your side. From 28 weeks, the safest position to go to sleep is on your side, either left or right. Research suggests that, after 28 weeks, falling asleep on your back can double the risk of stillbirth. This includes daytime naps. If you wake up on your back, just turn onto your side and go back to sleep.

Your week 29 checklist

This week:

Try gentle exercise or swimming to help with back pain.
Ask your midwife for a physiotherapy referral if needed.
Monitor for any sudden severe swelling.
Continue tracking your baby's movements.
Start writing a list of questions for your next antenatal appointment.

Sources & further reading

General information, not individual medical advice. Speak to your GP, midwife or health visitor about your baby’s needs.