What affects fertility?
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Medically reviewed on February 17, 2022 by Jordan Stachel, M.S., RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.
The process of getting pregnant can seem incredibly straightforward. An egg cell meets a sperm cell, and the miracle of life happens. In reality, there are countless different factors at work that can influence fertility and determine the viability of a pregnancy.
The factors that affect fertility are broad-ranging, encompassing everything from personal health, lifestyle factors, and time of the month. Learn more about what affects fertility in both partners below (and to check in on fertility-related hormones, consider taking the at-home Women's Fertility Test).
Diet
Diet can affect all aspects of your general health, including ovulation and sperm cell health. The exact effects of diet on male and female fertility still require further study, but researchers from Harvard T.H. Chan School of Public Health and Harvard Medical School have found that certain vitamins and minerals can positively affect fertility. For women trying to get pregnant naturally, they may benefit by consuming more:
- Folic acid
- Vitamin B12
- Omega-3 fatty acids [1]
For those receiving assisted reproductive technologies, a fertility diet high in either folic acid or isoflavones (plant-based estrogens) may be beneficial [2].
For male fertility, some studies suggest that antioxidants may be beneficial, but importantly, semen quality is an imperfect predictor for fertility [3].
Among all genders, research suggested that “healthy diets,” like the Mediterranean diet, could benefit fertility. Generally, you want to focus on whole grains, lean sources of protein (like fish, poultry, and plant-based protein), and larger servings of fruits and vegetables. The main foods you want to avoid are highly refined, processed foods containing added sugars, which may contribute to higher insulin levels that can potentially interfere with healthy ovulation. Trans fats can also harm fertility by contributing to insulin resistance.
If you make any significant changes to your diet, make sure that you consult your healthcare provider beforehand.
Age
As you get older, your chance of pregnancy decreases. In men, studies have found that semen quantity and quality peaks between the ages of 30 and 35 with a significant drop off after 55. These same studies also found that sperm motility was best before the age of 25, while after 55, sperm motility saw a 54 percent decrease. Sperm motility refers to how well sperm can move, which is essential in fertilizing the egg [4].
Age is also found to affect the genetic quality of male sperm. Older men tend to have more sperm with genetic defects that included:
- Higher chance of miscarriage
- Higher risk of stillbirth
- Higher risk of birth defects
This also ultimately contributed to a higher risk of infertility [4].
Age also affects fertility in women significantly. Women begin their lives with a fixed number of eggs when they are born, about 2 million on average. By the time they reach puberty, women typically only have 300,000 to 400,000 eggs. As they get older, that number drops due to the natural menstrual cycle [5]. Along with that decrease in eggs, there is an increase in abnormal chromosomes and a general decline in egg quality [6].
Related to fertility, age also presents higher health risks as women get older. Later pregnancies present with a higher risk of complications for the mother and the growing fetus [6].
That’s not to say that getting pregnant later in life is impossible. It is still possible, especially with assistive technologies. The chances are just much lower. By age 40, only about 1 in 10 women will get pregnant in any single menstrual cycle [5].
Hormonal Imbalances
Hormonal imbalances play a role in some infertility cases. Most people know that estrogen and progesterone play a big role, but any hormonal imbalances can ultimately hinder pregnancy. Imbalances in adrenal hormones, thyroid hormones, and prolactin can all contribute to fertility issues [7].
In men, any decrease in testosterone levels can affect fertility. Testosterone is important to your general health, but it plays an intrinsic role in sperm production, motility, and quality. Low testosterone may increase your risk of low or no sperm production [8].
Disorders and Diseases
A wide range of disorders and diseases can potentially contribute to fertility issues. Ovulation disorders, including polycystic ovarian syndrome (PCOS) and hyperprolactinemia, specifically interfere with the ability of ovaries to release eggs. Hyperthyroidism and hypothyroidism can also cause problems with your menstrual cycles [9].
Endometriosis is another common disorder that may contribute to female infertility. This disorder is characterized by endometrial tissue growing outside of the uterus. Endometriosis can affect the basic functions of the uterus, fallopian tubes, and ovaries, decreasing a woman's fertility chances [9].
Abnormalities in the uterus or cervix may also cause fertility problems, including:
- Polyps growing in the lining of the uterus
- An abnormally shaped uterus
- Uterine fibroids (noncancerous tumors appearing on the uterine wall) [9]
Any damage or blockage to the fallopian tubes can prevent proper ovulation. This is typically caused by salpingitis or inflammation in the fallopian tubes [9].
Stress
Excess stress can work in a few different ways to stifle any efforts at pregnancy and affect your overall health. Stress alters the function of the hypothalamus, which maintains homeostasis and manages numerous different systems in your body, including the hormones that signal your ovaries to release eggs every month. With continued stress, you may ovulate less frequently [10].
In men, chronic stress can affect your testosterone levels. Reduced testosterone naturally affects sperm production and quality [10].
Poor Sleep
Sleep is necessary to your basic existence. During sleep, your brain and organ systems rest and rejuvenate. That includes your endocrine system and hormones. Poor sleep can harm your hormone production. Studies show that melatonin, cortisol, and other hormones involved with your sleep-wake cycle are all regulated by the same part of the brain involved with dispensing reproductive hormones. Furthermore, the hormones that trigger ovulation and sperm maturing may be linked to your basic sleep-wake cycle [11].
Poor sleep can also alter your mood and behaviors, preventing you from having sex. You may be more irritable or simply too tired to take part in sex. Consistently poor sleep increases your risk of diabetes, cardiovascular disease, and other health issues that may reduce fertility [11].
Smoking
On top of increased risks of lung disease, heart disease, and certain forms of cancer, smoking can affect your eggs and sperm. Chemicals in cigarettes can speed up the rate at which you lose eggs, while men who smoke may reduce sperm quality, quantity, and motility while increasing the risk of abnormalities in sperm cells [12].
Even those trying via in vitro fertilization and other assistive reproductive methods may experience trouble when smoking. Damage to eggs may mean fewer eggs to collect, and they have 30 percent lower pregnancy rates compared to non-smokers [12].
Fertility can be a difficult and fickle thing. Even with a solid diet and a non-smoking lifestyle, your genetics can still contribute to pregnancy difficulties. Consider getting tested by your healthcare provider or with a home testing kit, like the Everlywell at-home Fertility Test, to gain insight into any underlying hormonal imbalances.
Related content
What is secondary infertility?
Can irregular periods cause infertility?
When to see a fertility specialist
References
1. Fertility and diet: Is there a connection? Harvard Health. URL. Accessed February 17, 2022.
2. Fertility Diet: What to Eat When Trying to Get Pregnant. Parents.com. URL. Accessed February 17, 2022.
3. Does Age Affect Male Fertility? Verywell Family. URL. Accessed February 17, 2022.
4. Levitas E, Lunenfeld E, Weisz N, Friger M, Potashnik G. Relationship between age and semen parameters in men with normal sperm concentration: analysis of 6022 semen samples. Andrologia. 2007 Apr;39(2):45-50. PMID: 17430422.
5. Female Reproductive System. Cleveland Clinic. URL. Accessed February 17, 2022.
6. Having a Baby After Age 35: How Aging Affects Fertility and Pregnancy. American College of Obstetricians and Gynecologists. URL. Accessed February 17, 2022.
7. Female infertility. Society for Endocrinology. URL. Accessed February 17, 2022.
8. Reproductive Infertility. Endocrine Society. URL. Accessed February 17, 2022.
9. Infertility - Symptoms and causes. Mayo Clinic. URL. Accessed February 17, 2022.
10. Stress Can Delay Pregnancy or Even Cause Infertility! Parents.com. URL. Accessed February 17, 2022.
11. How Lack of Sleep May Affect Your Fertility. Verywell Family. URL. Accessed February 17, 2022.
12. Smoking and Infertility. American Society for Reproductive Medicine. URL. Accessed February 17, 2022.