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3 Factors That Impact Egg Quality

3 Factors That Impact Egg Quality

Nancy Littleford | May 15, 2020 | Getting Pregnant
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Wouldn’t it be great if there was a foolproof way to evaluate human eggs quality and be able to use that information to help in the investigation as to the cause(s) of infertility issues? But alas, there is not. Though there are tests for the quantity of eggs in the ovaries, there aren’t reliable tests for quality, which means some assumptions have to be made about their viability from a quality standpoint (3). 

When a female fetus develops in the uterus, all of the eggs that she will ever have also develop. The number may range from 6 to 7 million eggs to begin with, but even before birth, those eggs begin to die off. By the time the baby is born, the amount of eggs is reduced to about 1 million. Of those, only about 300 to 400 eggs will be released in a woman’s lifetime during ovulation throughout her reproductive years (1). In this post, we examine 3 factors that contribute to egg quality during a woman’s fertile years. 

Lifestyle and fertility

Lifestyle makes a difference on egg quality, but to what extent is unclear (2). Here is what science tells us about lifestyle factors and egg quality: 

  • Smoking: Smoking has been proven to decrease egg quality. Tobacco-use in women who smoke more than 20 cigarettes a day will have “elevated hormones that indicate a depleted supply of eggs and prematurely aged follicles” (2). 
  • Diet: To contribute to the good health of the body to optimize the ability to conceive, it’s important to maintain a healthy weight, and eat foods that are high in folic acid, iron and vitamin C (which enhances the absorption of iron). Foods like: dark green leafy vegetables, beans, lentils, whole grains, and citrus fruits. Also eat more healthy fats like avocados, less meat protein and more vegetable protein and avoid low-fat dairy in favor of the high fat instead (7). 
  • Exercise: Physical health is an important component of fertility and maintaining a healthy weight through diet AND exercise is a vital factor in getting pregnant (8). 
  • Alcohol: Abstinence may be the only safe bet since alcohol use may impact ovulation and, of course, no amount of alcohol consumption is safe during pregnancy (10).
  • Stress: Stress produces a hormone called cortisol, which works to enhance our ability to engage in “flight or fight” activities and reduces functioning to any part of the human body that is not essential to survival, and one of those systems is reproduction (4). Stress and infertility go hand in hand. Cortisol can affect ovulation, creating fertility issues (9) and the fertility issues cause stress and produce more cortisol, creating a vicious cycle, so it’s important to manage stress.

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Toxins and fertility

It’s important to think about where you work, live, and play when considering factors that may impact the complexities of reproduction, and that includes harmful environmental exposure. This can include things like pesticides, toxic chemicals, highly concentrated dust particles (like in woodworking), solvents, lead, and X-rays are all negative culprits (2). 

Here are the top 5 toxins that have been clinically proven to impact fertility (8):

  1. Lead
  2. Pesticides and herbicides
  3. Polychlorinated biphenyls (PCBs) which can be found in items like certain plastics, oil-based paint, caulking, floor finishes (11)
  4. Dry cleaning chemicals
  5. Toxic cleaning products
Age and fertility

The only current reliable indication of egg quality, surprisingly enough, is age. The reason we know this is because of the high rate of successful pregnancies with the donated eggs of women in their 20’s versus the donated eggs of older women (4). The old cliché that a woman’s “biological clock is ticking” has some science to it. As our society has changed and evolved, the average age of marriage (5) and having children has increased (6), and with it, challenges with fertility. Unfortunately, the physically ideal age to have children hasn’t evolved with our changing lifestyle. 

Egg quality diminishes over time and occurs much earlier than many women think (4). While the exact age at which egg quality declines depends on the individual, on average fertility begins to drop in the late 20s or early 30s (4). The decline speeds up after age 35. The supporting evidence that age plays such a vital role in egg quality is in studies done that show a high success rate of pregnancy using donated eggs from women in their 20s (4). 

While age is the most determining factor for egg quality, and you can’t control for your age, it doesn’t mean you have nothing you can do. As long as you still have some eggs left, you can improve your lifestyle to increase your chances of getting pregnant — and of course get your partner involved too! 


  1. Cleveland Clinic. (2019). Female reproductive system.
  2. Barbieri, Robert L., Domar, Alice D., Loughlin, Kevin R. (2000). Making fertility-friendly lifestyle choices. Adapted from Six Steps to Increased Fertility: An Integrated Medical and Mind/Body Program to Promote Conception. Harvard Health Publishing.
  3. MacMillain, Carrie. (2018). Yale Medicine. Women, How Good are your Eggs? Retrieved from https://yalemedicine.org/stories/fertility-test/
  4. American Society for Reproductive Medicine. (2012). Age and Fertility Booklet. 5-8.
  5. United States Census Bureau.(2019, November). Historical Marital Tables. Retrieved from https://www.census.gov/data/tables/time-series/demo/families/marital.html. 
  6. Centers for Disease Control. Mathews, T.J., Hamilton, Brady E. (2016, January). NCHS Data Brief No. 232. Mean Age of Mothers is on the Rise: United States:, 2000-2014. (1).
  7. Academy of Nutrition and Dietetics. Kaufman, Caroline. (2020, April). Foods That Can Affect Fertility. Retrieved from https://www.eatright.org/health/pregnancy/fertility-and-reproduction/fertility-foods. 
  8. The National Infertility Association. The Impact of Environmental Factors, Body Weight and Exercise on Fertility. Retrieved from http://familybuilding.resolve.org/site/DocServer/EnvironmentalFactors.pdf?docID=261
  9. MU Health Care. 3 Ways to Cope with the Stress of Infertility. Retrieved from https://www.muhealth.org/our-stories/3-ways-cope-stress-infertility
  10. Mayo Clinic. Healthy Lifestyle, Getting Pregnant. Retrieved from https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/female-fertility/art-20045887
  11. United States Environmental Protection Agency. Learn about Polychlorinated Biphenyls (PCBs).
How Not to Waste Another Month When Trying to Conceive
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