Fetal Tachycardia

Overview

Fetal tachycardia means an unborn baby's heart is beating faster than usual. A baby's heart rate before birth is normally between about 110 and 160 beats per minute. Doctors call it fetal tachycardia when the rate stays above about 160 beats a minute for 10 minutes or longer. It is not a disease in itself — it is a signal that something may need checking. Most of the time the cause is something treatable, such as a fever in the mother, an infection, or simply a temporary response to movement or contractions.

It is not common. Brief speeding up of the baby's heartbeat is very common and usually normal. A heartbeat that stays fast for a long time is much less common and needs a check by the maternity team.

It can affect any unborn baby at any stage of pregnancy, but it is seen most often during labour or when the mother has a fever, an infection, or a thyroid condition. Some babies have a heart rhythm problem of their own, but this is rare.

Symptoms

Common symptoms

• Usually no symptoms at all — the fast heartbeat is found on a monitor, not felt by the mother
• The mother may notice signs of the underlying cause, such as a fever, chills, feeling unwell, or a racing feeling in her own chest
• Sometimes fewer baby movements than usual
• During labour, the maternity team may notice changes on the baby's heart-rate trace

Symptoms in children

• Not applicable — this condition is only found in babies who have not yet been born

Symptoms in older adults

• Not applicable — this condition only affects unborn babies

Causes

Main causes

• Fever or infection in the mother — the baby's heart speeds up in response, much as your own does when you are unwell
• Infection of the womb or around the time of birth (doctors call this chorioamnionitis — an infection of the tissues around the baby)
• An overactive thyroid gland in the mother
• Some medicines can raise the baby's heart rate as a side effect
• The baby being short of oxygen or having low blood count (anaemia — fewer red blood cells than normal)
• A heart rhythm problem in the baby, such as a very fast, regular rhythm coming from the upper chambers of the heart
• Pressure on the umbilical cord, or contractions during labour

Risk factors

• A fever or infection during pregnancy or labour
• Thyroid problems in the mother
• Certain medicines taken during pregnancy, including some used for asthma or to delay early labour
• Problems with the placenta or the baby's growth
• Twins or multiple pregnancy
• Long or difficult labour
• Some rare heart conditions in the baby

When to see a doctor

See a doctor urgently if:

• You have a fever, chills, or feel generally unwell during pregnancy
• Your baby's movements have slowed down or changed
• You have any bleeding, leaking fluid, or pain
• You have been told your baby's heartbeat was fast and you notice new symptoms before your next appointment

Book a routine appointment if:

• At any routine antenatal appointment, ask about your baby's heartbeat and how it is being checked
• If you have a thyroid condition or a long-term illness, tell your maternity team so they can keep an eye on things
• If you are taking regular medicines, check with your midwife or pharmacist that they are suitable in pregnancy

Diagnosis

The first step is usually listening to or monitoring your baby's heartbeat — during an antenatal check, or with a tracing machine in labour (a CTG, which records the heartbeat and contractions over time). If the rate stays high, the team will look for a cause. This means checking the mother's temperature, pulse, and blood pressure, asking about medicines and illnesses, and often doing an ultrasound scan of the baby. Sometimes a specialist scan of the baby's heart (a fetal echocardiogram — a detailed ultrasound of the heart) is arranged.

Tests that may be done

• Listening to the baby's heartbeat with a handheld device
• Continuous heart-rate monitoring (CTG) to see the pattern over time
• Ultrasound scan to check the baby's growth, movements, and fluid level
• Fetal echocardiogram — a detailed ultrasound of the baby's heart to check its structure and rhythm
• Blood tests on the mother to look for infection, thyroid problems, or anaemia
• Checks of the mother's temperature, pulse, and blood pressure

What to expect at your appointment

You may be asked to lie on your side and be monitored for a while — sometimes the rate settles simply with a change of position. Staff may give you fluids, check your temperature, and ask questions about how you have been feeling. If a cause such as a fever or infection is found, treatment usually starts quickly. In many cases you will be monitored more closely for a few hours, and you will be told what the team is seeing and why.

Treatment

Treatment depends on the cause, how fast the heart is beating, how far along the pregnancy is, and how well the baby is doing. Often the answer is to treat the underlying problem — for example, bringing down a fever or treating an infection — and the baby's heart rate settles. In other cases, closer monitoring or early delivery is the safest option. Your maternity team will explain the plan and involve you in decisions.

Self-care at home

• Take any fever-reducing medicine only as advised by your midwife, doctor, or pharmacist, and follow their guidance on what is safe in pregnancy
• Rest and drink plenty of fluids if you feel unwell or feverish
• Keep a note of your baby's usual movement pattern and report changes
• Attend all your antenatal appointments, even if you feel well
• Tell your team about all medicines, supplements, and remedies you take
• Ask questions — it is fine to ask what the monitor is showing and what happens next

Medical treatments

Doctors first look for and treat the cause. That may include bringing down a fever, giving fluids, or treating an infection with medicines prescribed by your doctor. If the mother has a thyroid problem, that is managed by a specialist team. If the baby has a fast heart rhythm of its own, a specialist fetal medicine team may recommend medicines given to the mother that cross the placenta and help slow the baby's heart — this is done only in specialist centres with close monitoring. Sometimes the team simply watches closely and plans the safest time and way for the baby to be born.

When is surgery considered?

If the baby's heart rate stays very fast and the baby is showing signs of struggling, the team may recommend delivering the baby early. This might be by starting labour with medicines (an induction) or by caesarean section — an operation to birth the baby through a cut in the mother's tummy. This decision is made together with you, based on how far along you are and how the baby is doing.

Living with this condition

Being told your baby's heartbeat is fast can be worrying, especially if you are already in labour or staying in hospital. In most cases you will be monitored closely and staff will keep you updated. If you are sent home, you may have extra appointments. Try to keep the rest of your life as calm and simple as you can, and lean on the people around you.

Lifestyle tips

• Get plenty of rest, especially if you have been unwell or feverish
• Stay well hydrated
• Avoid alcohol and smoking, and ask for help to stop if you smoke
• Keep moving gently if you feel well — ask your midwife what is right for you
• Write down questions between appointments so you remember to ask them

Diet and exercise

There is no special diet for fetal tachycardia, but eating regularly and drinking enough helps you feel better and supports your pregnancy. Gentle everyday activity, such as short walks, is usually fine if you feel well and your team has not advised otherwise. If you have been unwell or are being monitored in hospital, follow the advice of your midwife or doctor about activity.

Mental health and emotional wellbeing

Hearing that something is being checked with your baby can bring anxiety, and that is completely understandable. Anxiety during pregnancy is common, and support is available. Talking to your midwife about how you feel is a good first step — they can arrange extra support, and you do not have to cope alone. If you ever feel you cannot cope, or have thoughts of harming yourself, contact your local crisis line or emergency services right away.

Prevention

Not all cases can be prevented, especially those caused by a baby's own heart rhythm problem. But you can lower the chance of some causes: get early help for fever or infection, keep up with antenatal appointments, and tell your team about any long-term conditions such as thyroid problems or medicines you take.

Vaccines

Staying up to date with the vaccines recommended in pregnancy — such as flu and whooping cough — helps prevent infections that can cause fever and illness, which are among the triggers for a fast baby heartbeat. Ask your midwife or pharmacist which vaccines are recommended for you.

Screening programmes

Routine antenatal checks — including listening to your baby's heartbeat at each visit and monitoring in labour — are how fetal tachycardia is usually spotted. If you have a thyroid condition or another long-term illness, you may have extra monitoring. Tell your team about any change in your baby's movements between appointments.

Complications

If left untreated

• If a very fast heart rate continues for a long time, the baby's heart may not pump blood as efficiently as it should
• Fluid can build up in the baby's body — doctors call this hydrops, and it needs specialist care
• The baby may become short of oxygen or show signs of distress, which can mean earlier delivery
• In some cases the baby may need to be born early and cared for in a newborn unit for a while

Long-term outlook

The outlook is good for most babies. Many cases settle once the cause — such as a fever or infection — is treated, and the baby is born healthy. Even when a baby has a fast heart rhythm of its own, specialist teams are experienced at managing it, and most respond well to treatment. If your baby needs extra care after birth, the newborn team will explain what is happening at every step.

Find support

External links open third-party websites. Ruqelo Health is not responsible for external content. Listing an organisation does not imply endorsement.