Fertility is a fascinating topic that touches almost everyone’s lives in one way or another. It is an evolving field of study that can be clouded with misinformation, lack of education, and new findings that have altered some of our fundamental understanding of the science behind it. This is why we have brought in Dr. Ginevra Mills, an obstetrician gynecologist with a specialty in reproductive endocrinology and infertility with three kiddos of her own, to help us wade through some of this information starting with: Fertility as we Age!
While this may seem like a basic place to start, many people may carry some misconceptions about how infertility is defined. The true definition of infertility is the failure to conceive after twelve months of intercourse without contraception. This doesn't mean that you're actively trying to get pregnant for a year. This means that you are not taking a birth control pill or using any type of barrier contraception, like a condom, and you are having regular, unprotected intercourse and not getting pregnant within the span of a year.
What are the chances of getting pregnant per month (or each ovulation cycle)? In most people, if you're having unprotected sex and you're around your early to mid twenties, your chance of getting pregnant every month is only about 25%. This is not taking into consideration how our bodies change as we age out of the optimal fertility window, which we will talk about later on. Even when tracking our ovulation and fertility cycle and doing everything “perfectly,” healthy individuals have a maximum 25% chance of getting pregnant that month. If you add up that math, just under three months (25% + 25% + 25%) you have around a 60% chance of conceiving, and about a 75% chance after six months. While there is still a certain amount of chance involved - failure to conceive one cycle does not change the chances the next - cumulatively over time pregnancy occurs by the one year mark in about 85% of cases. This is why after 1 year, we would recommend seeking some help from a fertility specialist if you have not yet conceived.
At the age of 30, on average people’s chance of pregnancy every ovulation cycle goes down to about 20%. By the age of 35, it is about 15% per month. And by the age of 40, your chance of spontaneous pregnancy is only about 5% per month.
Why does this happen? People with ovaries are born with all of the eggs that are ever going to be released in their lifetime at the time of birth. In fact, the maximum number of eggs possessed is actually when people are at about 20 weeks gestation - meaning a 20 week old fetus! As we get older, much like all the cells in our body, our eggs are dying off and accumulating mutations just by the virtue of everyday living.
Without getting into too much scientific detail, when it comes time for eggs to ovulate, the older they are, the less well they function. That may mean that they can't be fertilized as well, or it might mean that they fertilize but there's something wrong with the machinery of the egg that doesn't allow it to develop into an embryo to implant. It might mean that it implants, but then it stops developing. Most of all, especially as women get over the age of 35, we start to see an increased risk of miscarriage as well as issues with the way the chromosomes separate. Last but not least, as people age all of our cells are changing throughout our body and we are more likely to develop medical issues such as Type-2 Diabetes or hypertension, which can play a factor in pregnancy as well.
The first sign that you're ovulating is having a regular period every month. A period is considered a regular cycle if it occurs anywhere between about 25 to 35 days. If it's within that range every month, regular periods are 97% predictive of ovulation occurring. As your ovaries start to diminish their number of eggs, fewer follicles have to do the same amount of work that a bigger group did in a younger person. As a result, they work harder, they do their job faster, and ovulation cycles might start getting a little bit shorter. If when you were 24 or 25 you had 28 day cycles all the time, and now at 30 you've noticed that your cycles are always about 26 days or 25 days, then that is something to look out for over the long term.
If you’d like to do a bit deeper dive into your fertility, you can consider taking an anti-mullerian hormone (AMH) test. AMH is a hormone produced by the follicles in your ovaries. When that number is high, it indicates a high number of follicles, but it does not necessarily predict current or future fertility potential. It is a helpful number for specialists to determine what kind of fertility treatment might be helpful and how your ovaries may respond, but it does not give magic insight into your fertility. Even with a lower ovarian reserve, one could have good, healthy eggs, and remember - it only takes one!
The answer to this question has seen quite a bit of change in recent years! It used to be thought that for people with sperm, age did not affect their reproductive abilities. Because sperm are constantly being reproduced in the testicles, unlike ovaries which carry a finite number of eggs, it was thought that their age was not a factor in reproductive health, though an individual with sperm over the age of 40 could be more likely to pass down a genetic abnormality such as autosomal dominant conditions like achondroplasia, or Huntington's disease. While changes in DNA could occur, generally it was believed that older sperm was not a factor in hindering pregnancy or a cause of miscarriage.
New studies have found, however, that when the male partner is over the age of 40, they have about a 25%-40% reduction in their success of pregnancy than they did when they were under the age of 30. Scientists are unsure of why that is the case, but a potential reason could be that the cells that create sperm - which are embryologically related to the same cells in ovaries that nourish eggs - are themselves getting older and therefore creating sperm that does not function as well.
Tune in in the following weeks where we will be continuing our conversation about fertility with Dr. Mills! But until then, feel free to follow her on Instagram, and check out The Pregnancy to Parenthood Podcast Series! For the low, one-time cost of $47, get full access to over 40 informative episodes supporting you week by week, focused on the trimester and stage of pregnancy you are in. Tune in every week, or binge listen all at once and come back to the episodes you found most helpful as you move through pregnancy to parenthood!