Fever during pregnancy: is it dangerous for my baby?

What temperature counts as a fever in pregnancy?

A fever is a temperature of 38 °C or higher, measured at rest with a reliable thermometer. Between 37.5 °C and 38 °C, it is simply a raised temperature: take it again a few hours later, without taking any medicine just before, so as not to mask how it changes.

During pregnancy, any confirmed fever calls for medical advice the same day. It is not the temperature itself that is most worrying, but what it may reveal. Your pregnancy care and the arrangements for your birth are described on the Giving birth in Paris page.

Write down your temperature, the time you took it and any other symptoms (burning when passing urine, cough, pain, contractions): this information is very helpful for the doctor or midwife who examines you.

What causes a fever when you are pregnant?

In the vast majority of cases, fever is caused by an infection. Some are minor; others need prompt treatment.

The most common infections

• Urinary infection and pyelonephritis: pregnancy makes urinary infections more likely. An infection that reaches the kidney (pyelonephritis) causes a high fever, chills and pain in the back, on one side. It can trigger contractions and often needs a hospital stay. See also urinary tract infections in women.
• Chest, ear, nose and throat infections: colds, sore throats, bronchitis, but also flu and COVID-19, which can be more severe during pregnancy.
• Gastroenteritis: the main risk is dehydration.

Infections that can reach the baby

• Listeriosis: a food-borne infection, rare but serious in pregnancy. It may show up as a fever alone, sometimes with aching, which is why you should see a doctor even for a fever "with no obvious reason".
• Viral infections: cytomegalovirus, toxoplasmosis, rubella, chickenpox, parvovirus B19, hepatitis. They are tested for depending on the situation and your previous blood test results (see CMV and pregnancy).
• Malaria: any fever after returning from a tropical area is an emergency, even several months after the trip.

Pregnancy-related infections

Chorioamnionitis is an infection of the membranes and amniotic fluid. It mainly occurs after your waters have broken or late in pregnancy. It is an obstetric emergency.

Non-infectious or surgical causes

Appendicitis or cholecystitis (inflammation of the gallbladder) can cause fever and abdominal pain. More rarely, an inflammatory or autoimmune disease is involved; it is then managed with a specialist, together with the obstetric team.

Is a fever dangerous for my baby?

Most often, a short fever that is treated and has a minor cause has no consequences for the baby. The risks depend on three things: the cause, the stage of pregnancy and how long the fever lasts.

According to a meta-analysis (Dreier, 2014), fever in the first trimester increases the risk of neural tube defects, heart defects and cleft lip and palate by 1.5 to nearly 3 times; medicines that lower fever may reduce this risk. For other effects, particularly on the child's neurological development, the evidence is insufficient to draw conclusions. These findings are a reason to treat fever.

For the mother, an untreated infection can become more serious: severe pyelonephritis, sepsis, dehydration. Treatment therefore protects both mother and baby.

What should I do if I have a fever while pregnant?

1. Check your temperature with a reliable thermometer.
2. Drink regularly and rest.
3. Paracetamol is the standard painkiller and fever reducer throughout pregnancy. Use the lowest effective dose for the shortest possible time, following the leaflet or your doctor's advice. A large Swedish study comparing siblings found no link between paracetamol taken during pregnancy and autism, ADHD or intellectual disability.
4. Never take ibuprofen, aspirin above 100 mg a day or any other anti-inflammatory (NSAID) on your own: these medicines must not be used from the 6th month of pregnancy, even as a single dose and even as a gel or patch; before that, they are only taken if prescribed by a doctor. See medicines and pregnancy.
5. Contact your doctor, your midwife or the maternity unit the same day to find the cause.

Paracetamol lowers your temperature but does not treat the cause: a fever that comes down with paracetamol still needs to be explained.

Which tests are done and how is the cause treated?

The examination includes taking your temperature, blood pressure and pulse, a general and obstetric examination and, depending on the stage of pregnancy, listening to the baby's heart or recording the baby's heart rate (CTG monitoring).

Tests often requested

• Urine dipstick and urine culture.
• Blood tests: blood count, inflammation markers, sometimes blood cultures. With an unexplained fever, blood cultures look in particular for listeriosis.
• Targeted antibody tests depending on the situation.
• Vaginal swab, and a malaria test after returning from an area where it is common.
• Pregnancy ultrasound if needed.

Treatment

• Bacterial infection: antibiotics that are safe in pregnancy, by mouth or in hospital depending on how serious it is. An unexplained fever in a pregnant woman may justify treatment against listeriosis while waiting for results.
• Flu: an antiviral medicine can be prescribed promptly for pregnant women.
• Surgical cause: an operation is still possible during pregnancy, decided jointly by the surgeon, the anaesthetist and the obstetrician.

When is a fever in pregnancy an emergency?

Go straight to the maternity unit's emergency department where you are registered (Sainte-Félicité or Sainte-Thérèse) or call 15 (SAMU) or 112 in France, or your local emergency number, if the fever comes with any of these signs:

• severe chills, feeling faint, confusion or a fever above 39 °C despite paracetamol;
• pain in the back or side, burning when passing urine;
• abdominal pain, regular contractions or a hard abdomen;
• fluid leaking from the vagina, or bleeding;
• reduced baby movements;
• difficulty breathing, chest pain;
• a severe headache, stiff neck or skin rash;
• vomiting that stops you keeping fluids down;
• a recent return from a tropical country, even with a moderate fever.

Without these signs, an appointment the same day is enough. If the fever lasts more than 24 hours despite treatment, see a doctor again.

How can I lower my risk of fever during pregnancy?

• Vaccination against flu and COVID-19, which are recommended during pregnancy in France (see vaccines and pregnancy).
• Food safety to prevent listeriosis and toxoplasmosis: avoid raw-milk cheeses, deli meats sliced at the counter, smoked fish and undercooked meat; wash fruit and vegetables (see preventing toxoplasmosis).
• Frequent handwashing, especially after contact with young children (saliva, urine, nappies) to reduce the risk of CMV.
• Drinking enough and passing urine regularly to reduce urinary infections.
• Before travelling to a tropical area, ask for medical advice on preventing malaria.

Frequently asked questions

General information article: it does not replace a medical consultation. In an emergency, call 15 or 112 in France, or your local emergency number.