Is There A Relationship Between Pregnancy And Breast Cancer Risk
Studies have shown that a womans risk of developing breast cancer is related to her exposure to hormones that are produced by her ovaries . Reproductive factors that increase the duration and/or levels of exposure to ovarian hormones, which stimulate cell growth, have been associated with an increase in breast cancer risk. These factors include early onset of menstruation, late onset of menopause, and factors that may allow breasttissue to be exposed to high levels of hormones for longer periods of time, such as later age at first pregnancy and never having given birth.
Conversely, pregnancy and breastfeeding, which both reduce a womans lifetime number of menstrual cycles, and thus her cumulative exposure to endogenous hormones , are associated with a decrease in breast cancer risk. In addition, pregnancy and breastfeeding have direct effects on breast cells, causing them to differentiate, or mature, so they can produce milk. Some researchers hypothesize that these differentiated cells are more resistant to becoming transformed into cancer cells than cells that have not undergone differentiation .
What Are The Risk Factors For Breast Cancer
Being a woman and getting older are the main risk factors for breast cancer.
Studies have shown that your risk for breast cancer is due to a combination of factors. The main factors that influence your risk include being a woman and getting older. Most breast cancers are found in women who are 50 years old or older.
Some women will get breast cancer even without any other risk factors that they know of. Having a risk factor does not mean you will get the disease, and not all risk factors have the same effect. Most women have some risk factors, but most women do not get breast cancer. If you have breast cancer risk factors, talk with your doctor about ways you can lower your risk and about screening for breast cancer.
Why Dont All Of The Studies Agree
Induced abortion brings up many strong feelings in people, so it is often hard to study its long-term effects.
Before 1973, induced abortions were illegal in much of the United States. So when researchers asked a woman about past pregnancies, she may not have felt comfortable saying that she had an abortion. Even though abortion is now legal, it is still a very personal, private matter that many women do not like to talk about. This means that many women might not report having an abortion if asked for a study. In contrast, women with breast cancer are more likely to accurately report their reproductive histories, including a history of having an abortion. This recall bias could lead to retrospective studies finding links that arent found in prospective studies. Still, not everyone agrees that this is the reason that the different types of studies conflict.
In general, though, when prospective and retrospective studies conflict, experts generally accept the results of the prospective studies over the retrospective studies.
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Breast Cancer Risk Factors
A risk factor is anything that affects your chance of getting a disease, such as cancer. Most women who have one or more breast cancer risk factors never develop the disease, while many women with breast cancer have no apparent risk factors . Even when a woman with risk factors develops breast cancer, it is hard to know just how much these factors may have contributed to her cancer.
There are different kinds of risk factors. Some factors, like a person’s age or race, can’t be changed. Others are linked to cancer-causing factors in the environment. Still others are to related personal behaviors, such as smoking, drinking, and diet. Some factors influence risk more than others, and your risk for breast cancer can change over time, due to factors such as aging or lifestyle.
Studies have found the following risk factors for breast cancer:
How Is Breast Density Measured
When you have a mammogram, a radiologist reads the results using the Breast Imaging Reporting and Data System, or BI-RADS, published by the American College of Radiology. This is a standard system for reporting whats seen on the imaging.
BI-RADS uses an assessment scale from 1 through 6 to indicate whether there were no unusual findings or, if something was found, whether it was more likely benign or malignant . The report will also give a recommendation for routine screening or indicate what follow-up tests may be needed. An assessment of 0 means that additional imaging is first needed in order to characterize a potential finding.
In the BI-RADS report, the radiologist also includes a score for breast density on a scale from A through D:
A) Mostly fatty: The breasts are made up of mostly fatty tissue and contain very little fibrous and glandular tissue. About 10% of women have fatty breasts.
B) Scattered fibroglandular densities: The breasts are mostly fatty tissue, but there are a few areas of fibrous and glandular tissue visible on the mammogram. About 40% of women have scattered density.
C) Heterogeneously dense: A mammogram shows many areas of fibrous and glandular tissue. About 40% of women get this result.
D) Extremely dense: The breasts have large amounts of fibrous and glandular tissue. About 10% of women fall into this category.1
From left to right: BI-RADS categories A through D
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If You Have Had Breast Cancer Before
In this case, you will have regular follow-up appointments. Any changes in the same breast or the other breast can be checked quickly.
Having certain breast conditions can also increase the risk of developing breast cancer:
- Lobular carcinoma in situ
LCIS is also called lobular neoplasia. This is when there are abnormal cell changes in the lining of the lobules.
- Atypical ductal hyperplasia
This is when there are slightly abnormal-looking cells in the milk ducts in a small area of the breast.
Women with these non-cancerous conditions are usually monitored regularly, so any changes can be found early.
Caution With Hormone Replacement Therapy
For most women, menopause begins at age 45. The production of the sex hormones estrogen and progestin then decreases. This can cause hot flashes, sleep disturbances and mood swings. Some women then turn to hormone preparations they can relieve these symptoms. However, a team of researchers found in 2019 that such hormone replacement therapy increases the risk of breast cancer in the long term. Therefore, treatment should preferably not last longer than one year.
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Personal History Of Early Breast Cancer
Women diagnosed with invasive breast cancer are at a higher risk of developing cancer in their other breast.
There are also a number of non-invasive breast conditions that are associated with an increased risk of breast cancer. These include ductal carcinoma in situ , lobular carcinoma in situ and atypical ductal hyperplasia .
Risk Of Developing Breast Cancer
The term risk is used to refer to a number or percentage that describes how likely a certain event is to occur. When we talk about factors that can increase or decrease the risk of developing breast cancer, either for the first time or as a recurrence, we often talk about two different types of risk: absolute risk and relative risk.
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What Factors Put You At High Risk For Breast Cancer
Doctors consider several factors to determine if youre at a high risk of breast cancer. All of these factors, except for pregnancy history and radiation exposure, are things you cannot change:
- Family history: If youve had one or more close relatives, such as parents, siblings, or children with breast cancer, your risk increases.
- Genetics: Having inherited gene mutations that are associated with family cancer syndromes, particularly those in BRCA1 or BRCA2, significantly boost your risk of developing breast cancer.
- Age: The risk of breast cancer goes up as you get older.
- Personal history: A personal history of certain breast conditions raises your breast cancer risk. These include:
Remember that theres no standardized way to determine breast cancer risk. While breast cancer risk assessment tools are important in helping to estimate risk, they typically dont take all of the factors above into account.
Hair Products And Skin Creams
You want to do your skin good and give your hair a new look. However, hair products and creams regularly fail the “”kotest” because they contain questionable substances. Dr. Alice Martin, dermatologist and co-founder of the Dermanostic telemedicine practice, gives only a partial all-clear: The studies are very scarce when it comes to a connection between breast cancer and hair products or skincare. All ingredients are tolerable in moderation, but can of course have a carcinogenic effect in a certain quantity. In the area of hair care and skincare, however, there is currently no ingredient that science explicitly warns against worldwide
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Using The Oral Contraceptive Pill
A number of studies suggest a womans breast cancer risk is increased while she is taking the oral contraceptive pill and for up to 10 years after stopping it. For most young women in their 20s and 30s the increase in risk is small, but for older women and those with other strong risk factors the risk may be greater.
Chemicals In Cosmetics Food And In Plastic
There is some concern that exposure to phthalates, specifically, may increase a woman’s risk of developing breast cancer, but the data on this issue aren’t clear.
Phthalates can be found in medical supplies, food containers, cosmetics, toys, some medications. Aside from this, there is no evidence that exposure to other chemicals increases a womans risk of developing breast cancer.
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Factors That Affect Breast Cancer Risk
Some factors affect breast cancer risk a great deal and others by only a small amount.
Understanding which factors may affect your risk of breast cancer can help you work with your health care provider to address any concerns you have and develop a breast cancer screening plan thats right for you.
Our Breast Cancer Risk Factors Table compares risk factors by level of risk and strength of evidence.
Factors that affect breast cancer risk are listed below alphabetically.
Age is a risk factor for breast cancer in both women and men. The older a person is, the more likely they are to get breast cancer.
Learn more about age and breast cancer risk.
Both the age when a woman gives birth to her first child and the number of children a woman has affect her risk of breast cancer.
Women who give birth to their first child at age 35 or younger tend to get a protective benefit from pregnancy .
In general, the more children a woman has given birth to, the lower her risk of breast cancer tends to be .
Learn more about age at first childbirth, number of childbirths and breast cancer risk.
Starting menstrual periods at a young age is linked to a small increase in breast cancer risk .
For example, women who begin their periods before age 11 have about a 15-20 percent higher breast cancer risk compared to those who begin their periods at age 15 or older .
Going through menopause at a later age is linked to an increased risk of breast cancer .
Learn more about breast cancer in men.
Is Abortion Linked To Breast Cancer Risk
A few retrospective studies reported in the mid-1990s suggested that induced abortion was associated with an increased risk of breast cancer. However, these studies had important design limitations that could have affected the results. A key limitation was their reliance on self-reporting of medical history information by the study participants, which can introduce bias. Prospective studies, which are more rigorous in design and unaffected by such bias, have consistently shown no association between induced abortion and breast cancer risk . Moreover, in 2009, the Committee on Gynecologic Practice of the American College of Obstetricians and Gynecologists concluded that more rigorous recent studies demonstrate no causal relationship between induced abortion and a subsequent increase in breast cancer risk . Major findings from these studies include:
- Women who have had an induced abortion have the same risk of breast cancer as other women.
- Women who have had a spontaneous abortion have the same risk of breast cancer as other women.
- Cancers other than breast cancer also appear to be unrelated to a history of induced or spontaneous abortion.
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What Are The Most Common Risk Factors For Breast Cancer
The following risk factors have the strongest evidence behind them and are recognized as clearly affecting breast cancer risk, for better or worse.
To see more risk factors, including possible risk factors that are currently under study, visit Susan G. Komens website. There are also lots of things that are rumored to increase breast cancer risk but have been shown by research not to. Susan G. Komen has a list of those factors too.
Being Overweight Or Obese
Women who are overweight after their menopause have a higher risk of breast cancer than women who are not overweight. Men also have an increased risk of breast cancer if they are overweight or obese. For both men and women, the risk increases as more weight is gained.
Body mass index is a measure that uses your height and weight to work out whether you are a healthy weight. For most adults, an ideal is between 18.5 to 24.9. Being overweight means having a BMI of between 25 and 30. Obesity means being very overweight with a BMI of 30 or higher.
Try to keep a healthy weight by being physically active and eating a healthy, balanced diet.
Drinking alcohol increases the risk of breast cancer in women. The risk increases with each extra unit of alcohol per day. The number of units in a drink depends on the size of the drink, and the volume of alcohol.
The latest UK government guidelines advise drinking no more than 14 units of alcohol a week.
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Having Certain Benign Breast Conditions
Women diagnosed with certain benign breast conditions may have a higher risk of breast cancer. Some of these conditions are more closely linked to breast cancer risk than others. Doctors often divide benign breast conditions into 3 groups, depending on how they affect this risk.
Non-proliferative lesions: These conditions dont seem to affect breast cancer risk, or if they do, the increase in risk is very small. They include:
- Fibrosis and/or simple cysts
- Mild hyperplasia
- Epithelial-related calcifications
- Other tumors
Mastitis is not a tumor and does not increase the risk of breast cancer.
Proliferative lesions without atypia : In these conditions theres excessive growth of cells in the ducts or lobules of the breast, but the cells don’t look very abnormal. These conditions seem to raise a womans risk of breast cancer slightly. They include:
- Usual ductal hyperplasia
- Several papillomas
- Radial scar
Proliferative lesions with atypia: In these conditions, the cells in the ducts or lobules of the breast tissue grow excessively, and some of them no longer look normal. These types of lesions include:
Breast cancer risk is about 4 to 5 times higher than normal in women with these changes. If a woman also has a family history of breast cancer and either hyperplasia or atypical hyperplasia, she has an even higher risk of breast cancer.
For more information, see Non-cancerous Breast Conditions.
Lobular carcinoma in situ
What Is Breast Cancer
Breast cancer occurs when a normal cell in the breast becomes abnormal and begins to grow out of control. The cancer can grow into a lump in the breast and can eventually spread to other places in the body such as the bones, lungs, liver, or brain. Breast cancer most often affects women, yet can also be diagnosed in men.
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Risk Factors You Can Change
- Not being physically active. Women who are not physically active have a higher risk of getting breast cancer.
- Being overweight or obese after menopause. Older women who are overweight or obese have a higher risk of getting breast cancer than those at a normal weight.
- Taking hormones. Some forms of hormone replacement therapy taken during menopause can raise risk for breast cancer when taken for more than five years. Certain oral contraceptives also have been found to raise breast cancer risk.
- Reproductive history. Having the first pregnancy after age 30, not breastfeeding, and never having a full-term pregnancy can raise breast cancer risk.
- Drinking alcohol. Studies show that a womans risk for breast cancer increases with the more alcohol she drinks.
Research suggests that other factors such as smoking, being exposed to chemicals that can cause cancer, and changes in other hormones due to night shift working also may increase breast cancer risk.
Reproductive History Estrogen Is The Main Hormone Associated With Breast Cancer Estrogen Affects The Growth Of Breast Cells Experts Believe That It Plays An Important Role In The Growth Of Breast Cancer Cells As Well The Type Of Exposure And How Long Cells Are Exposed To Estrogen Affects The Chances That Breast Cancer Will Develop
The start of menstruation is called menarche. Early menarche is when menstruation starts at an early age . Starting your period early means that your cells are exposed to estrogen and other hormones for a greater amount of time. This increases the risk of breast cancer.
Menopause occurs as the ovaries stop making hormones and the level of hormones in the body drops. This causes a woman to stop menstruating. If you enter menopause at a later age , it means that your cells are exposed to estrogen and other hormones for a greater amount of time. This increases the risk for breast cancer. Likewise, menopause at a younger age decreases the length of time breast tissue is exposed to estrogen and other hormones. Early menopause is linked with a lower risk of breast cancer.
Late pregnancy or no pregnancies
Pregnancy interrupts the exposure of breast cells to circulating estrogen. It also lowers the total number of menstrual cycles a woman has in her lifetime.
Women who have their first full-term pregnancy after the age of 30 have a slightly higher risk of breast cancer than women who have at least one full-term pregnancy at an earlier age. Becoming pregnant at an early age reduces breast cancer risk.
The more children a woman has, the greater the protection against breast cancer. Not becoming pregnant at all increases the risk for breast cancer.
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