Fetal Bradycardia

Overview

Fetal bradycardia means an unborn baby's heart is beating more slowly than usual. 'Fetal' means unborn baby, 'brady' means slow, and 'cardia' means heart. A baby's heart normally beats between about 110 and 160 times a minute. Doctors usually call it bradycardia when the rate stays below 110 beats a minute. It is not a disease in itself — it is a sign that something may need checking. Sometimes it is a brief, harmless dip during labour. Other times it lasts longer and needs medical attention.

Brief dips in a baby's heart rate during labour are very common and are usually not a sign of a problem. A slow heart rate that lasts a long time, or is found during pregnancy rather than labour, is much less common.

It affects unborn babies at any stage of pregnancy, and most often it is noticed during routine antenatal checks or during monitoring in labour. It is not something the pregnant person can feel happening, so it is found by a midwife or doctor rather than by you.

Symptoms

Common symptoms

• Usually there are no symptoms at all — the slow heartbeat is only found when a midwife or doctor listens to the baby's heart or uses a monitor.
• Sometimes the only clue is that the baby is moving less than usual.
• During labour, staff may notice dips in the heart rate on the tracing monitor, particularly around contractions.

Symptoms in children

• Not applicable — this condition happens before birth, in an unborn baby. After birth, a slow heart rate in a newborn is a different situation and is checked by the baby's doctor.

Symptoms in older adults

• Not applicable — this condition only affects unborn babies.

Causes

Main causes

• A problem with the electrical signal that tells the baby's heart to beat, called congenital heart block — the heart's natural 'pacemaker' does not pass the signal on properly.
• A structural heart defect — how the baby's heart is formed.
• Medicines taken by the mother that can cross the placenta and slow the baby's heart, such as some treatments for high blood pressure or heart conditions.
• Low blood pressure in the mother, which reduces blood flow to the placenta.
• Problems with the placenta, such as it not working as well as it should.
• Pressure on the umbilical cord, for example when it is squeezed during a contraction or if it slips down ahead of the baby.
• Contractions that are very strong or very close together, sometimes caused by medicines used to start or speed up labour.
• Rarely, infections, low blood sugar or low body temperature in the mother, or a genetic condition in the baby.

Risk factors

• The mother having an autoimmune condition such as lupus or Sjögren's syndrome, especially with certain antibodies that can affect the baby's heart
• A previous baby with heart block or a heart defect
• Family history of congenital heart disease
• Diabetes in pregnancy
• A twin or multiple pregnancy
• A baby who is growing more slowly than expected
• Long or complicated labour, or labour that has been started or sped up with medicines
• The umbilical cord coming down before the baby, or the placenta separating early

When to see a doctor

See a doctor urgently if:

• You notice your baby is moving less than usual or the pattern has changed — ring your maternity unit immediately, at any hour
• Any vaginal bleeding
• Waters breaking before 37 weeks
• Regular painful contractions before 37 weeks
• A high temperature, or feeling generally very unwell

Book a routine appointment if:

• Your midwife or doctor has mentioned a slow heartbeat on a check and you want to understand what it means
• You are taking a regular medicine and want to check it is safe in pregnancy — ask your GP, midwife or pharmacist before making any changes yourself
• You have an autoimmune condition and are planning a pregnancy or are already pregnant
• You feel anxious about your baby's heartbeat or your monitoring appointments and want to talk it through

Diagnosis

Fetal bradycardia is found by listening to or monitoring the baby's heartbeat. During pregnancy this is done at your antenatal appointments; during labour the heartbeat is usually tracked continuously or at regular intervals. If the rate is low or the pattern looks unusual, the team will look for the cause. That can include checking your blood pressure, medicines, blood sugar and temperature, watching how the heart rate responds to contractions, and using ultrasound to look at the baby's heart.

Tests that may be done

• Listening to the baby's heartbeat with a handheld device (a fetal stethoscope or Doppler)
• Electronic monitoring in labour, called a CTG (cardiotocograph), which records the heartbeat and contractions on a paper or screen tracing
• Ultrasound scan to check the baby's growth, movements and the amount of fluid around them
• Fetal echocardiogram — a detailed ultrasound of the baby's heart, done by a specialist
• Blood tests for you, such as checking for certain antibodies linked to heart block, blood sugar, infection markers or blood count
• A review of all your medicines with your doctor or pharmacist
• Sometimes a sample of the baby's blood during labour, taken by a specialist, to check oxygen levels

What to expect at your appointment

If a slow heartbeat is picked up, staff will usually ask you to lie on your side, check your blood pressure and pulse, and keep watching the tracing. These first steps often settle things within minutes. If the rate stays low or the tracing is concerning, a senior doctor will talk with you about what is happening and what the options are, including closer monitoring, further tests, or — depending on how far along you are and how the baby is doing — planning an earlier birth. You should always feel able to ask questions.

Treatment

What happens next depends on the cause, how low the heart rate is, how long it lasts, and how many weeks pregnant you are. A brief dip in labour often needs only simple measures and settles by itself. A slow rate found during pregnancy, or one that keeps coming back, needs a specialist team to look at the baby's heart and plan care together with you.

Self-care at home

• Go to all your antenatal and monitoring appointments, even if you feel well
• Learn your baby's usual movement pattern, and contact your maternity unit the same day if it changes — do not use a home Doppler to check the heartbeat yourself, as it can give false reassurance
• In later pregnancy, lying on your side rather than flat on your back helps blood flow to the placenta
• Keep well hydrated and eat regularly, especially in labour
• Check any medicine with your GP, midwife or pharmacist — never stop or change a prescribed medicine on your own
• Write down your questions before appointments, and take someone with you if it helps
• Ask your team what to do and who to ring if you are worried at night or at the weekend

Medical treatments

Treatment is aimed at the cause. During labour, simple steps come first: changing your position, fluids, and stopping any medicine that is making contractions very strong. Your blood pressure, blood sugar, temperature and oxygen levels are checked and treated if needed. If the baby's heart rate stays low and there are signs the baby is short of oxygen, the team may recommend delivering the baby sooner, either with help during labour or by caesarean. If the cause is a heart block found during pregnancy, you will be cared for by a fetal medicine and paediatric cardiology team; they may suggest medicines for you (chosen by your specialist) and plan the birth so that the right newborn team is there. Some babies with heart block need a small device fitted after birth to keep the heart beating at a steady rate.

When is surgery considered?

A caesarean birth may be recommended if the baby's heartbeat shows they are not coping well and a vaginal birth would take too long. If a baby is born with a heart block, they may need a short procedure after birth to fit a pacemaker — a small device that keeps the heart beating regularly. Your team will explain the reasons, the risks and the alternatives before anything goes ahead.

Living with this condition

Most parents find the waiting and monitoring the hardest part. You may have extra appointments, scans and heart tracings, and your birth plan may change. Try to keep the practical side simple: a bag packed a little earlier, a clear list of who to ring, and someone who can come with you. Ask your midwife to write down the plan so you can look back at it when you are tired or worried.

Lifestyle tips

• Keep up gentle everyday activity unless your team advises otherwise
• Avoid smoking, alcohol and recreational drugs, and ask for help to stop if you need it
• Get plenty of rest, and accept practical help from friends and family
• Keep taking any prescribed medicines, and check new ones — including over-the-counter remedies and supplements — with a pharmacist
• Attend all monitoring appointments, and keep your maternity notes with you

Diet and exercise

Eat regular balanced meals and drink enough water. There is no special diet that changes a baby's heart rate, but keeping your blood sugar steady matters if you have diabetes in pregnancy — follow the advice of your diabetes team. Gentle activity such as walking, swimming or antenatal classes is usually fine; ask your midwife if you need to adapt anything.

Mental health and emotional wellbeing

It is completely normal to feel frightened or to keep replaying monitoring appointments in your head. Anxiety during pregnancy is common, and it does not mean you are coping badly. Talk to your midwife — they can explain things again, slow the pace down, or refer you for extra support. If low mood, panic or intrusive worry is affecting your sleep or daily life, tell your GP or maternity team; help is available and it is not a sign of weakness. If you ever feel you cannot keep yourself safe, contact your local emergency number or a crisis line straight away.

Prevention

Not all cases can be prevented, and it is important to know that nothing you did caused this. Some causes can be reduced: having your medicines reviewed before and during pregnancy, keeping blood pressure and blood sugar well controlled, and attending monitoring appointments if you have an autoimmune condition. If you are planning a pregnancy and take regular medicine, ask your GP or pharmacist to review it first — never stop a medicine on your own.

Screening programmes

Routine antenatal care includes listening to the baby's heartbeat and, for some people, extra checks. If you have an autoimmune condition such as lupus or Sjögren's, your team may offer blood tests for certain antibodies and repeat ultrasound scans of the baby's heart during pregnancy. During labour, monitoring the baby's heartbeat is the main way of spotting a slow rate early.

Complications

If left untreated

• If a baby is short of oxygen for a long time, there is a risk of harm to the brain and other organs
• A heart block that is not recognised can lead to heart failure in the baby before birth, with extra fluid building up
• In serious cases, an untreated prolonged slow heart rate can increase the risk of stillbirth — this is why monitoring and acting on changes matter so much
• Being born early, if delivery is needed urgently, can bring its own challenges for the baby
• Some babies need ongoing heart checks and, occasionally, a pacemaker as they grow

Long-term outlook

The outlook is good for most babies. Short dips in heart rate during labour are very common and usually resolve with simple measures, and babies are rarely affected afterwards. Babies with heart block or a heart defect are followed closely by specialist teams and many do very well with modern care. Your team will be honest with you about what they see on the monitor and what it means for your baby, and they will plan care with you rather than for you.

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