﻿ bumps - best use of medicine in pregnancy


(Date: September 2019. Version: 3)




What is ondansetron?

Ondansetron is a medicine used to treat nausea and/or vomiting. Ondansetron is normally prescribed for severe pregnancy sickness when other treatments have not worked.

Is it safe to take ondansetron in pregnancy?


What if I have already taken ondansetron during pregnancy?

There is no need to worry if you have already taken ondansetron, since the risk to the baby is very small. However, you may wish to discuss this further with your midwife, GP or obstetrician.

Can taking ondansetron in pregnancy cause my baby to be born with birth defects?

A baby’s body and most internal organs are formed during the first 12 weeks of pregnancy. It is mainly during this time that some medicines are known to cause birth defects. Use of a medicine after week 12 of pregnancy would not be expected to cause structural problems in the baby.

Cleft lip and/or palate
Research suggests that babies whose mothers are taking ondansetron between weeks six and twelve of pregnancy may have a slightly higher chance of cleft lip and/or palate than unexposed babies. Around 11 in every 10,000 babies are born with cleft lip and/or palate every year (this is called the background rate). This increases to 14 in every 10,000 babies exposed to ondansetron in the womb.


Heart defects
There has been some evidence that babies exposed to ondansetron may have a higher chance of having a heart defect. However, a large study did not show any increase in structural heart disease, more evidence is still needed.

Can taking ondansetron in pregnancy cause miscarriage, preterm birth, my baby to be small at birth (low birth weight), or stillbirth?

There is no evidence that women who take ondansetron during pregnancy are more likely to have a miscarriage, a premature baby, a low birth weight baby or a stillbirth.

Can taking ondansetron in pregnancy cause learning or behavioural problems in the child?

Two studies have investigated learning and behaviour in a total of 350 children exposed to ondansetron in the womb and neither study identified any significant problems. While this is reassuring, ongoing research is required.

Will my baby need extra monitoring during pregnancy?

No extra monitoring of your baby is needed.

Are there any risks to my baby if the father has taken ondansetron?

We would not expect any increased risk to your baby if the father took ondansetron before or around the time you became pregnant.

Who can I talk to if I have questions?


Feedback request 


General information 


Medicines use in pregnancy








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