Promethazine

What is it?

Promethazine (Phenergan®) is a sedating (drowsy) antihistamine that is used to treat allergies, nausea and vomiting (including in pregnancy), and for short-term treatment of some sleep problems.

When deciding whether to use promethazine during pregnancy it is important to weigh up the potential benefits to your health and wellbeing against any possible risks to you or your baby, some of which may depend on how many weeks pregnant you are. Your doctor or specialist will be able to help you make decisions about your treatment.

What if I have already taken promethazine during pregnancy?

If you are taking any medicines while pregnant you can discuss this with your doctor. You can then decide together whether ongoing treatment is appropriate, and, if so, your doctor will ensure that you are taking the most effective dose.

Can taking promethazine in pregnancy cause birth defects in the baby?

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.

Over 5,000 women taking promethazine in early pregnancy have been studied as it is used quite commonly to treat pregnancy sickness. These studies do not raise concern of a link with birth defects in the baby.

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

No studies have specifically assessed the likelihood of these pregnancy outcomes in women taking promethazine in pregnancy. Although ongoing research is ideally required to rule out any problems, promethazine is quite widely used in pregnancy and so any common adverse effects would likely have been identified.

Can taking promethazine in pregnancy cause learning and behavioural problems in the child?

A baby’s brain continues to develop right up until the end of pregnancy. It is therefore possible that taking certain medicines at any stage of pregnancy could have a lasting effect on a child’s learning or behaviour.

No studies have assessed the learning and behaviour of children exposed in the womb to promethazine.

Will my baby need extra monitoring?

Most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects as part of their routine antenatal care. Taking promethazine in pregnancy would not normally require extra monitoring of your baby. 

Exposure in the womb to promethazine in the two weeks prior to delivery may lead to temporary changes to the baby’s nervous system that can affect their behaviour for a few days after birth, The baby may cry more, be jittery, respond differently to stimuli, and be harder to settle. Women who have taken promethazine around the time of delivery may therefore be advised to have their baby in a unit with facilities to monitor the baby and offer any required treatment.

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

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

Who can I talk to if I have questions?

If you have any questions regarding the information in this leaflet please discuss them with your health care provider. They can access more detailed medical and scientific information from www.uktis.org.