Oral contraceptives

(Date: November 2018. Version: 2)

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.

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What are oral contraceptives?

There are two types of oral contraceptive. 

The first, often called ‘the combined pill’ or ‘the pill’, contains synthetic versions of two hormones, oestrogen and progesterone.

The second type of oral contraceptive, known as the ‘progestogen-only pill’ or ‘the mini pill’ contains synthetic progesterone only.

Different brands of oral contraceptive may contain hormones in different forms and strengths.

There is quite a lot of information about babies whose mothers took oral contraceptives whilst pregnant. However, most studies have looked at oral contraceptives as a group rather than trying to examine the effects of each type of pill separately. The findings of these studies are summarised below.

Can taking oral contraceptives 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.

Studies of large numbers of pregnant women do not prove that there is a link between oral contraceptive use in early pregnancy and birth defects in the baby.

Oral contraceptives contain sex hormones, and so some studies have specifically looked at whether taking oral contraceptives during early pregnancy may affect the development of a baby’s sex organs. There is no scientific proof from these studies that women taking oral contraceptives during pregnancy are more likely to have a baby with abnormal sex organs, or to have a baby boy with hypospadias (where the opening of the penis is not in the usual place).

While some studies have suggested a possible link between oral contraceptive use in pregnancy and having a baby with limb reduction defects (shortened or missing arms or legs), the majority of studies have not shown this. Experts agree that the available information does not prove a link but that ongoing research is ideally required.

Can taking oral contraceptives in pregnancy cause miscarriage?

No increased chance of miscarriage was identified in three studies of women who took oral contraceptives during pregnancy. While this is reassuring, because only around 1,800 women were studied, further research into the likelihood of miscarriage is ideally required.

Can taking oral contraceptives in pregnancy cause preterm birth or my baby to be small at birth (low birth weight)?

Two studies have investigated whether preterm birth may be linked to exposure to oral contraceptives in early pregnancy. The studies each produced different results. More research is therefore needed to determine whether the link identified in one study was due to oral contraceptive use itself, or to other factors that may have been more common in women who had taken oral contraceptives in early pregnancy (see below).

There is also mixed evidence as to whether taking oral contraceptives in early pregnancy may be linked to low birth weight in the baby (<2,500 g). While two studies have shown a possible link, one further study did not.  

Pregnancies in women taking the contraceptive pill are generally unplanned and may not be detected until later. Women who do not realise they are pregnant are unlikely to be following pregnancy lifestyle advice. This may explain why some studies have found that babies of women taking oral contraceptives in pregnancy are more likely to be born earlier and be smaller.

Can taking oral contraceptives in pregnancy cause stillbirth?

No studies have specifically investigated whether stillbirth is more common following use of oral contraceptives in pregnancy.

Can taking oral contraceptives 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.

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

Will my baby need extra monitoring?

As part of their routine antenatal care most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects and to check the baby’s growth.

Extra monitoring of your baby is not required if you have taken oral contraceptives during pregnancy.

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 healthcare provider. They can access more detailed medical and scientific information from www.uktis.org

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WE NEED YOUR HELP! Do you have 3 minutes to complete a short, quick and simple 12 question user feedback form about our bumps information leaflets? To have your say on how we can improve our website and the information we provide please visit www.surveymonkey.co.uk/r/uktis-bumps.

General information 

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.

   

www.medicinesinpregnancy.org

Disclaimer: This information is not intended to replace the individual care and advice of your health care provider. New information is continually becoming available. Whilst every effort will be made to ensure that this information is accurate and up to date at the time of publication, we cannot cover every eventuality and the information providers cannot be held responsible for any adverse outcomes following decisions made on the basis of this information. We strongly advise that printouts should NOT be kept for any length of time, or for “future reference” as they can rapidly become out of date.

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