Many women worry hormonal contraceptives have dangerous side-effects including increased cancer risk. But this perception is often out of proportion with the actual risks.

So, what does the research actually say about cancer risk for contraceptive users?

And is your cancer risk different if, instead of the pill, you use long-acting reversible contraceptives? These include intrauterine devices or IUDs (such as Mirena), implants under the skin (such as Implanon), and injections (such as Depo Provera).

Our new study, conducted by the University of Queensland and QIMR Berghofer Medical Research Institute and published by the Journal of the National Cancer Institute, looked at this question.

We found long-acting contraceptives seem to be as safe as the pill when it comes to cancer risk (which is good news) but not necessarily any safer than the pill.

How does the contraceptive pill affect cancer risk?

The International Agency for Research on Cancer, which compiles evidence on cancer causes, has concluded that oral contraceptives have mixed effects on cancer risk.

Using the oral contraceptive pill:

• slightly increases your risk of breast and cervical cancer in the short term, but
• substantially reduces your risk of cancers of the uterus and ovaries in the longer term.

Our earlier work showed the pill was responsible for preventing far more cancers overall than it contributed to.

In previous research we estimated that in 2010, oral contraceptive pill use prevented over 1,300 cases of endometrial and ovarian cancers in Australian women.

It also prevented almost 500 deaths from these cancers in 2013. This is a reduction of around 25% in the deaths that could have occurred that year if women hadn’t taken the pill.

In contrast, we calculated the pill may have contributed to around 15 deaths from breast cancer in 2013, which is less than 0.5% of all breast cancer deaths in that year.

What about long-acting reversible contraceptives and cancer risk?

Long-acting reversible contraceptives – which include intrauterine devices or IUDs, implants under the skin, and injections – release progesterone-like hormones.

These are very effective contraceptives that can last from a few months (injections) up to seven years (intrauterine devices).

Notably, they don’t contain the hormone oestrogen, which may be responsible for some of the side-effects of the pill (including perhaps contributing to a higher risk of breast cancer).

Use of these long-acting contraceptives has doubled over the past decade, while the use of the pill has declined. So it’s important to know whether this change could affect cancer risk for Australian women.

Our new study of more than 1 million Australian women investigated whether long-acting, reversible contraceptives affect risk of invasive cancers. We compared the results to the oral contraceptive pill.

We used de-identified health records for Australian women aged 55 and under in 2002.

Among this group, about 176,000 were diagnosed with cancer between 2004 and 2013 when the oldest women were aged 67. We compared hormonal contraceptive use among these women who got cancer to women without cancer.

We found that long-term users of all types of hormonal contraception had around a 70% lower risk of developing endometrial cancer in the years after use. In other words, the risk of developing endometrial cancer is substantially lower among women who took hormonal contraception compared to those who didn’t.

For ovarian cancer, we saw a 50% reduced risk (compared to those who took no hormonal contraception) for women who were long-term users of the hormone-containing IUD.

The risk reduction was not as marked for the implants or injections, however few long-term users of these products developed these cancers in our study.

As the risk of endometrial and ovarian cancers increases with age, it will be important to look at cancer risk in these women as they get older.

What about breast cancer risk?

Our findings suggest that the risk of breast cancer for current users of long-acting contraceptives is similar to users of the pill.

However, the contraceptive injection was only associated with an increase in breast cancer risk after five years of use and there was no longer a higher risk once women stopped using them.

Our results suggested that the risk of breast cancer also reduces after stopping use of the contraceptive implants.

We will need to follow-up the women for longer to determine whether this is also the case for the IUD.

It is worth emphasising that the breast cancer risk associated with all hormonal contraceptives is very small.

About 30 in every 100,000 women aged 20 to 39 years develop breast cancer each year, and any hormonal contraceptive use would only increase this to around 36 cases per 100,000.

What about other cancers?

Our study did not show any consistent relationships between contraceptive use and other cancers types. However, we only at looked at invasive cancers (meaning those that start at a primary site but have the potential to spread to other parts of the body).

A recent French study found that prolonged use of the contraceptive injection increased the risk of meningioma (a type of benign brain tumour).

However, meningiomas are rare, especially in young women. There are around two cases in every 100,000 in women aged 20–39, so the extra number of cases linked to contraceptive injection use was small.

The French study found the hormonal IUD did not increase meningioma risk (and they did not investigate contraceptive implants).

Benefits and side-effects

There are benefits and side-effects for all medicines, including contraceptives, but it is important to know most very serious side-effects are rare.

A conversation with your doctor about the balance of benefits and side-effects for you is always a good place to start.

Susan Jordan, Professor of Epidemiology, The University of Queensland; Karen Tuesley, Postdoctoral Research Fellow, School of Public Health, The University of Queensland, and Penny Webb, Distinguished Scientist, Gynaecological Cancers Group, QIMR Berghofer Medical Research Institute

This article is republished from The Conversation under a Creative Commons license. Read the original article.

What’s the difference? is a new editorial product that explains the similarities and differences between commonly confused health and medical terms, and why they matter.

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Former US First Lady Michelle Obama revealed in her memoir she had a miscarriage. UK singer-songwriter and actor Lily Allen has gone on the record about her stillbirth.

Both miscarriage and stillbirth are sadly familiar terms for pregnancy loss. They can be traumatic life events for the prospective parents and family, and their impacts can be long-lasting. But the terms can be confused.

Here are some similarities and differences between miscarriage and stillbirth, and why they matter.

Let’s start with some definitions

In broad terms, a miscarriage is when a pregnancy ends while the fetus is not yet viable (before it could survive outside the womb).

This is the loss of an “intra-uterine” pregnancy, when an embryo is implanted in the womb to then develop into a fetus. The term miscarriage excludes ectopic pregnancies, where the embryo is implanted outside the womb.

However, stillbirth refers to the end of a pregnancy when the fetus is normally viable. There may have been sufficient time into the pregnancy. Alternatively, the fetus may have grown large enough to be normally expected to survive, but it dies in the womb or during delivery.

The Australian Institute of Health and Welfare defines stillbirth as a fetal death of at least 20 completed weeks of gestation or with a birthweight of at least 400 grams.

Internationally, definitions of stillbirth vary depending on the jurisdiction.

How common are they?

It is difficult to know how common miscarriages are as they can happen when a woman doesn’t know she is pregnant. There may be no obvious symptoms or something that looks like a heavier-than-normal period. So miscarriages are likely to be more common than reported.

Studies from Europe and North America suggest a miscarriage occurs in about one in seven pregnancies (15%). More than one in eight women (13%) will have a miscarriage at some time in her life.

Around 1–2% of women have recurrent miscarriages. In Australia this is when someone has three or more miscarriages with no pregnancy in between.

Australia has one of the lowest rates of stillbirth in the world. The rate has been relatively steady over the past 20 years at 0.7% or around seven per 1,000 pregnancies.

Who’s at risk?

Someone who has already had a miscarriage or stillbirth has an increased risk of that outcome again in a subsequent pregnancy.

Compared with women who have had a live birth, those who have had a stillbirth have double the risk of another. For those who have had recurrent miscarriages, the risk of another miscarriage is four-fold higher.

Some factors have a u-shaped relationship, with the risk of miscarriage and stillbirth lowest in the middle.

For instance, maternal age is a risk factor for both miscarriage and stillbirth, especially if under 20 years old or older than 35. Increasing age of the male is only a risk factor for stillbirth, especially for fathers over 40.

Similarly for maternal bodyweight, women with a body mass index or BMI in the normal range have the lowest risk of miscarriage and stillbirth compared with those in the obese or underweight categories.

Lifestyle factors such as smoking and heavy alcohol drinking while pregnant are also risk factors for both miscarriage and stillbirth.

So it’s important to not only avoid smoking and alcohol while pregnant, but before getting pregnant. This is because early in the pregnancy, women may not know they have conceived and could unwittingly expose the developing fetus.

Why do they happen?

Miscarriage often results from chromosomal problems in the developing fetus. However, genetic conditions or birth defects account for only 7-14% of stillbirths.

Instead, stillbirths often relate directly to pregnancy complications, such as a prolonged pregnancy or problems with the umbilical cord.

Maternal health at the time of pregnancy is another contributing factor in the risk of both miscarriage and stillbirths.

Chronic diseases, such as high blood pressure, diabetes, hypothyroidism (underactive thyroid), polycystic ovary syndrome, problems with the immune system (such as an autoimmune disorder), and some bacterial and viral infections are among factors that can increase the risk of miscarriage.

Similarly mothers with diabetes, high blood pressure, and untreated infections, such as malaria or syphilis, face an increased risk of stillbirth.

In many cases, however, the specific cause of pregnancy loss is not known.

How about the long-term health risks?

Miscarriage and stillbirth can be early indicators of health issues later in life.

For instance, women who have had recurrent miscarriages or recurrent stillbirths are at higher risk of cardiovascular disease (such as heart disease or stroke).

Our research has also looked at the increased risk of stroke. Compared with women who had never miscarried, we found women with a history of three or more miscarriages had a 35% higher risk of non-fatal stroke and 82% higher risk of fatal stroke.

Women who had a stillbirth had a 31% higher risk of a non-fatal stroke, and those who had had two or more stillbirths were at a 26% higher risk of a fatal stroke.

We saw similar patterns in chronic obstructive pulmonary disease or COPD, a progressive lung disease with respiratory symptoms such as breathlessness and coughing.

Our data showed women with a history of recurrent miscarriages or stillbirths were at a 36% or 67% higher risk of COPD, respectively, even after accounting for a history of asthma.

Why is all this important?

Being well-informed about the similarities and differences between these two traumatic life events may help explain what has happened to you or a loved one.

Where risk factors can be modified, such as smoking and obesity, this information can be empowering for individuals who wish to reduce their risk of miscarriage and stillbirth and make lifestyle changes before they become pregnant.

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More information and support about miscarriage and stillbirth is available from SANDS and Pink Elephants.

Gita Mishra, Professor of Life Course Epidemiology, Faculty of Medicine, The University of Queensland; Chen Liang, PhD student, reproductive history and non-communicable diseases in women, The University of Queensland, and Jenny Doust, Clinical Professorial Research Fellow, School of Public Health, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.