The Relationship Between Age and Fertility
When I got married at 32, I assumed I had a lot of childbearing years ahead of me before entering the “geriatric” world. But 4 years later, when I had my first appointment at a fertility clinic, I was warned that I had in fact entered the “advanced maternal age” phase (geriatric for short) when I turned 35.
It feels as though “prime reproductive age” was built on an old-school theory when life spans were far shorter than they are today. We all hear growing up that we have a proverbial biological clock associated with the aging of our ovaries and a guided timeline to procreate before a woman’s fertility declines. But, since on average we marry later, fulfill dreams later, and ideally travel the world or get a third collegiate degree before being “tied down,” shouldn’t our bodies as modern “older women” cooperate as well?
The Cleveland Clinic explains that advanced maternal age is “a pregnancy where the birthing person is older than 35. Pregnant people over age 35 are more at risk for complications like miscarriage, congenital disorders and high blood pressure.” But it’s important to understand the why in all of this, so let’s investigate.
We know it takes a quality egg and some beautifully swimming sperm to make an embryo and ultimately a pregnancy. Therefore, the quality of both the egg and the sperm are crucial to conception.
Half the story: the eggs
Females are born with all the eggs they’ll ever have. A fetus early in development with ovaries has around 6 million eggs. As it grows, the amount of eggs decreases until birth. Once the baby is born, it has approximately 2 million eggs.
Even though I probably learned this many times in school, when I was finally trying to conceive and was reminded that whatever I had in my ovaries was what we were working with to become pregnant, my mind was blown all over again.
A timeline exists because the quality and the quantity of our eggs decrease with age. The chance of pregnancy every month is between 25% and 30% during a woman’s early to mid-20s. Generally, fertility declines approaching her mid-30s, and especially after the age of 35. By age 40, the chance of pregnancy is around 5% each month.
Each monthly menstrual cycle releases at least one egg during ovulation, which is trying to get fertilized and become a baby. Many other eggs die and reabsorb into the body at that time, having been too immature for potential fertilization.
The quality of an egg is determined primarily by its chromosomes. The wrong number of chromosomes can lead to abnormal embryos, which leads to lack of proper development in fertilization, pregnancy, and/or developmental challenges if the baby is born.
Eggs have a hefty job once fertilized to split and divide their cells. Chromosomes don’t stick together as well in aging eggs. Because of this reduced cohesion, they prematurely separate during cell division. This leads to eggs with the wrong number of chromosomes, known as aneuploidy. Eggs with aneuploidy are usually infertile.
The other half of the story: the sperm
Paternal age matters too. The truth is that like female fertility, male fertility also takes a dip with age. Forty is the average age a man’s sperm quality begins to decrease.
Along with the fact that older men usually have older female partners, increasing male age also increases conception time. This is because age-related medical conditions increase, semen quality declines, and DNA fragmentation rates increase in sperm. Additionally, the age of the male partner is linked to birth defects and chromosomal abnormalities.
When we look for promising sperm, the main factors being examined are the shape or formation (morphology), the speed of swim (motility), the concentration of actual sperm within seminal fluid, and the volume of sperm being released. Men are not born with all of their sperm. Sperm are created and regenerated in real time, daily in fact. But true regeneration and maturation takes around 2 to 3 months.
Quantity is a far less common issue for men experiencing fertility challenges, as millions and sometimes billions of sperm are produced regularly. Quality, however, is extremely important and often the greater challenge. Each day, men produce millions of sperm, but men over 40 have fewer healthy sperm than younger men. Between the ages of 20 and 80, sperm motility and the amount of semen continuously decreases.
So what can we do about it all?
The good news is that there are options. Like all things in human reproduction, education is power.
This may mean starting some of the basic fertility tests at a younger age and continuing until ready to be done having children. There are diagnostic blood tests that measure reproductive hormones, overall egg count, and thyroid function. Having an understanding of these numbers sooner would allow us to plan accordingly, long before menopause. A woman who finds out that she has a low egg count and a high stimulating hormone in her twenties learns that she may have reproductive challenges later on and can manage expectations and take action to get pregnant and have a baby.
The general rule from the American College of Obstetricians and Gynecologists (ACOG) is to try naturally for one year if you’re under 35, or six months if over 35 before seeking medical or fertility treatments. In my version of the plan, if these tests were done earlier and more often than in your mid-30s, and processing the numbers was part of annual doctors’ visits and well-documented guidelines, the goal posts would move in favor of empowered fertility success rates and away from infertility.
Making the most of our fertility as we age:
Assisted reproductive technology (IVF treatments, fertility preservation)
Reproductive medicine has made lightning leaps in a short time; therefore there are options that involve fertility specialists (or reproductive endocrinologists). Talk to your doctor about ways to combat age-related infertility, such as genetic testing of embryos. They’ll be able to share the pros and cons, with the understanding that chromosomal abnormalities can be one of the leading causes of infertility in aging women. Your doctor can help to explain that while utilizing IVF (in vitro fertilization), they’re able to test embryos and transfer only those embryos with the correct number of chromosomes, often leading to the best chance for a successful outcome.
Additionally, when sperm is a factor contributing to infertility, using advanced reproductive technology techniques like a sperm wash or intracytoplasmic sperm injection (ICSI, when sperm is injected directly into an egg to optimize fertilization chances) helps age become less of a barrier, as all best possible opportunities are offered.
When given more information sooner, women could also learn about preservation (egg freezing) earlier. Again, since women are born with all of the eggs they’re ever going to have, retrieving and storing them externally via cryopreservation (literally freezing!) allows the eggs to remain the age and state that they were when they were retrieved, optimizing chromosomally normal embryos.
Third-party reproduction
As we continue to break stigmas of infertility, donor-assisted reproduction is an effective option gaining popularity. “Third-party reproduction” means involving someone other than the couple or individual who will raise the child in the reproduction process. Examples include using donated eggs, sperm, or embryos and gestational-carrier arrangements, in which someone else carries the pregnancy rather than the intended parent(s).
Many of the issues that arise in this “older” age group may be circumvented with a third party. If a donor’s eggs are 25 years of age, then the increased risk of abnormality at age 40 goes away. There is a lot to consider with third-party reproduction, but knowing that it is an option can be comforting.
Overall, I wish I could say that the advances in medicine mean that so many of these age-related challenges to procreation have gone away. While they still exist, there is so much more comfort in knowing that there are paths to take…some of those paths are considered unconventional, but in due time they will be the more traveled way. I am more than OK with that—but what does a geriatric know?
