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Medicine & Fertility

Understanding your fertility and what options are available to you is the most valuable tool to help you build the future you envision.  

Age-related Fertility Decline

Age-related fertility decline is a biological phenomenon and is not unique to the medical community. However, due to the demands of a career in medicine, physicians and physician-trainees have been shown to delay childbearing longer than their non-physician counterparts and therefore may be at increased risk for infertility and adverse pregnancy outcomes. Survey-based research shows that as many as 1 in 4 female physicians experience infertility.

Our goal is to provide you with the necessary information so you can make informed choices about your own family plan.

How does age affect eggs vs. sperm?

Biological females

A female is born with a fixed number of eggs in their ovaries, also known as “the ovarian reserve”. As a female ages,  both the quality and quantity of eggs declines. This decline begins at the age of 30 and accelerates at the age of 35. Quality of eggs refers to the chromosomal make-up of eggs. The number of chromosomally abnormal eggs at the age of 30 is 25%. This number increases to 80-90% by the age of 40. This can lead to difficulties with infertility and miscarriage.

Biological males 

For males, there is no “testicular reserve” as males produce 100-200 million sperm each day. However, sperm can still be affected by age. Both sperm motility and morphology decrease with age. Male age >40 is also associated with miscarriage, autosomal dominant disorders, schizophrenia and autism-spectrum disorders. 

How does age affect fertility?

Biological females

Fertility is primarily related to a biological female’s age. Between the late teens and late 20s, a female’s likelihood of conceiving is the highest, around 25% each month. The chances of getting pregnant each month begin to decline to about 20% each month, starting at the age of 30. At age 35, fertility starts to decline more rapidly. In the early 40s, there is only about a 5% chance of conceiving each month and by the mid 40s, there is a 1% chance of conceiving each month.

Can we get more specific? Yes - this table identifies the fecundability (the probability of conception in a month/menstrual cycle) for the first cycle, and on average. Importantly, it demonstrates at 14% decline in fecundability for females aged 34-35, a 19% decline for females aged 36-37, a 30% decline for females aged 38-39 and a 53% decline for females aged 40-41. It also illustrates the cumulative pregnancy rate over 6 cycles of trying to conceive and 12 cycles of trying to conceive. It also illustrates the difference in fecundability and cumulative pregnancy rates between nulligravid (females who have never been pregnant) and females with a history of prior pregnancy. 

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Table citation : Steiner AZ, Jukic AMZ. Impact of female age and nulligravidity on fecundity in an older reproductive age cohort. Fertility and Sterility [Internet]. 2016 Jun [cited 2022 Oct 31];105(6):1584-1588.e1. Available from:

Biological males 

Male age-related fertility decline is much less dramatic and predictable than that of females. However, studies have shown that males over the age of 40 were associated with 30% lower likelihood of conception in one year compared to males under 30.

Age-Related Fertility Decline & IVF

Many people view In vitro fertilization (IVF) as a treatment for age-related infertility. The truth is that IVF cannot overcome age-related fertility decline. This can be seen in the graph below, which looks at IVF success at various ages compared to using donor eggs from a younger individual. Since IVF relies on your own eggs, the quantity and quality of a female's eggs, which is impacted by age, will still affect the outcome.

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Image Citation : Canadian Assisted Reproductive Technologies Registry (CARTR) Plus. Final treatment cycle and pregnancy outcome data for 2020. Better Outcomes Registry & Network Ontario. Ottawa ON, September 2022.

How does Age affect Pregnancy?

Advancing age can also lead to increased pregnancy complications. Miscarriage rates, related to egg quality & the chromosomal make-up of the pregnancy, rise with age. Pregnancy loss rates are 7-15% for females less than 30, 8-21% for females aged 30-34, 17-28% for females aged 35-39 and 34-52% for females over 40. Pregnancy in females > 40 is associated with an increased rate of stillbirth, gestational diabetes, preeclampsia, intrauterine growth restriction and low birth weight. ​

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