(Date of issue: June 2015. Version: 1)
This factsheet has been written for members of the public by the UK Teratology Information Service (UKTIS). UKTIS is a not-for-profit organisation funded by Public Health England on behalf of UK Health Departments. UKTIS has been providing scientific information to health care providers since 1983 on the effects that medicines, recreational drugs and chemicals may have on the developing baby during pregnancy.
What is it?
Methyldopa (Aldomet®) is used to treat high blood pressure (hypertension). Medicines that are used to treat high blood pressure are sometimes referred to as antihypertensives. There are several different groups of antihypertensives that work in very different ways. Methyldopa belongs to a group called alpha-adrenergic agonists.
Is it safe to take methyldopa in pregnancy?
There is no yes or no answer to this question. When deciding whether or not to take methyldopa during pregnancy it is important to weigh up how necessary methyldopa is to your health against the possible risks to you or your baby, some of which will depend on how many weeks pregnant you are. For some women treatment with methyldopa in pregnancy may be considered necessary.
This leaflet summarises the scientific studies relating to the effects of methyldopa on a baby in the womb. It is advisable to consider this information if you are taking methyldopa and are pregnant or could become pregnant in the future.
Your doctor is the best person to help you decide what is right for you and your baby.
What if I have already taken methyldopa during pregnancy?
Methyldopa is often used to treat high blood pressure that is diagnosed during pregnancy. Some women who were being treated for high blood pressure before they fell pregnant may also be advised by their doctor to switch from their regular antihypertensive medicine to methyldopa. If you have taken or are taking any medicines it is still a good idea to let your doctor know that you are pregnant so that you can decide together whether you still need the medicines that you are on and, if so, to make sure that you are taking the lowest dose that works and only for as long as you need to.
It is very important that you do not suddenly stop taking methyldopa as this could be dangerous to you, and also to your baby if you are already pregnant. Do not make any change to your medication without first talking to your doctor.
Can taking methyldopa 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.
Studies have shown that untreated high blood pressure during pregnancy may increase a woman’s chance of having a baby with certain birth defects including heart defects and hypospadias (where the opening on the penis is on the underside rather than at the tip). It is therefore quite complicated to separate out whether use of antihypertensive medicines in pregnancy may cause birth defects in the baby or whether the birth defects are linked to the mother’s high blood pressure.
Birth defects have been studied in only a very small number of babies born to women who took methyldopa in pregnancy. One study suggested possible links between use of methyldopa in pregnancy and defects of the digestive tract, genital tract, or urinary tract. No other studies have examined possible links between these birth defects and methyldopa use in pregnancy, and it is not possible to say whether there are links based on the results of just one study. A second study showed that both women taking methyldopa and women with untreated high blood pressure were at increased risk of having a baby with a rare heart defect called Ebstein’s Anomaly, suggesting that this may be linked to the mother having hypertension and not to the methyldopa. A third study found no link between use of methyldopa in pregnancy and hypospadias or heart malformations in the baby.
Much more detailed research is required to separate out the effects of hypertension in pregnancy so that the risk (if any) to a baby of medicines used to treat high blood pressure in pregnancy can be assessed more accurately.
Can taking methyldopa in pregnancy cause miscarriage?
No link between methyldopa use in pregnancy and miscarriage is known about, although no scientific studies have been carried out that have specifically investigated this.
Can taking methyldopa in pregnancy cause stillbirth?
Seven of the eight studies that investigated this outcome did not find increased stillbirth rates in pregnancies where the mother had taken methyldopa. A further study that combined and analysed information from three earlier studies showed that women with high blood pressure in pregnancy who were treated with methyldopa were in fact less likely to experience a stillbirth or death of their baby soon after birth than pregnant women with untreated high blood pressure.
Can taking methyldopa in pregnancy cause preterm birth or my baby to be small at birth (low birth weight)?
Studying whether high blood pressure medicines increase the risk of a baby being born preterm or with a low birth weight can be difficult. This is because high blood pressure itself is thought to increase the risk of these pregnancy outcomes. Most of the studies that take into account the effects of the mother’s high blood pressure do not show than taking methyldopa in pregnancy increases the risk of preterm delivery or low birth weight in the baby.
Can taking methyldopa in pregnancy cause learning or 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.
Four studies have all showed that children who were exposed to methyldopa in the womb were no more likely to have problems with thinking, learning and behaviour than children who were not exposed to methyldopa. Although these findings are reassuring, there are many areas of child development that have not yet been studied in children exposed in the womb to methyldopa. More research is therefore required before we can say whether methyldopa use in pregnancy can cause changes in thinking, learning and behaviour in exposed children.
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 methyldopa in pregnancy is not expected to cause problems that would require extra monitoring of your baby. However, women with high blood pressure may be more closely monitored during pregnancy to ensure that they remain well throughout and that their baby is growing and developing as expected.
Are there any risks to my baby if the father has taken methyldopa?
We would not expect any increased risk to your baby if the father took methyldopa 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.
Up to 1 out of every 5 pregnancies ends in a miscarriage, and 1 in 40 babies are born with a birth defect. These are referred to as the background population risks. They describe the chance of these events happening for any pregnancy before taking factors such as the mother’s health during pregnancy, her lifestyle, medicines she takes and the genetic make up of her and the baby’s father into account.
Medicines use in pregnancy
Most medicines used by the mother will cross the placenta and reach the baby. Sometimes this may have beneficial effects for the baby. There are, however, some medicines that can harm a baby’s normal development. How a medicine affects a baby may depend on the stage of pregnancy when the medicine is taken. If you are on regular medication you should discuss these effects with your doctor/health care team before becoming pregnant.
If a new medicine is suggested for you during pregnancy, please ensure the doctor or health care professional treating you is aware of your pregnancy.
When deciding whether or not to use a medicine in pregnancy you need to weigh up how the medicine might improve your and/or your unborn baby’s health against any possible problems that the drug may cause. Our bumps leaflets are written to provide you with a summary of what is known about use of a specific medicine in pregnancy so that you can decide together with your health care provider what is best for you and your baby.
Every pregnancy is unique. The decision to start, stop, continue or change a prescribed medicine before or during pregnancy should be made in consultation with your health care provider. It is very helpful if you can record all your medication taken in pregnancy in your hand held maternity records.