These days, American women in their mid-to-late 30s are giving birth at a higher rate than women in their 20s, according to the latest data from the U.S. Centers for Disease Control and Prevention (CDC) (1).
Waiting until your 30s to have a baby is understandable, as women (and men!) focus on other life goals such as traveling, completing an education, and establishing a career. But delaying parenthood also may make you wonder — or worry! — whether you can actually get pregnant once you start trying. Here, we answer your most pressing questions about age and fertility by exploring the science of whether it’s harder to get pregnant in your 30s or not.
According to the American College of Obstetricians and Gynecologists (ACOG), a woman is most fertile in her late teens to late 20s (2). Female fertility declines significantly beginning around age 32, then decreases more rapidly after age 37, according to both ACOG and the American Society for Reproductive Medicine (ASRM) (3).
Statistically, a woman over the age of 35 will need to try twice as long as a woman under the age of 25 to get pregnant (4). How does age-related fertility decline look in any given cycle? According to ASRM, a healthy, fertile 30-year-old woman has a 20% chance of getting pregnant in any given cycle in which she tries. This means that in a group of 100 30-year-olds who are trying to get pregnant in a single cycle, 20 would become pregnant, and 80 would need to try again the next month (5).
By age 40, these odds drop to less than a 5% likelihood of success per cycle, according to ASRM — meaning that fewer than 5 out of every 100 women would be expected to become pregnant during a given cycle (5).
In contrast, the New England Journal of Medicine and BMJ, among the most esteemed peer-reviewed journals, found the odds of conception per cycle to be 12% at age 35 and 6% at age 42 (6).
Keep in mind that different statistics reflect a snapshot in time, based on data gathered from a specific set of women in a study group or a data set. Consider these numbers as guideposts that can help to explain how female fertility may change with age. In reality, your experience — or that of your bestie, sister, or cousin — may differ.
Or, as one scientist explains, “when assessing the effects of aging on fertility, it would be better to consider the patient's ovarian reserve rather than merely her chronological age (6).” Ovarian reserve refers to your own unique supply of healthy eggs.
As the years pass, normal age-related changes cause a decline in both the quality and quantity of eggs. A woman is born with roughly 1 million egg-containing follicles, but loses two-thirds of these follicles by the time she enters puberty. Out of the 300,000 or so remaining follicles, only around 300 will be ovulated during your childbearing years (5).
What happens to those hundreds of thousands of lost follicles? Most disintegrate in an ongoing process of degeneration called atresia, which unfortunately can’t be controlled. Atresia occurs regardless of whether you have “normal” menstrual cycles or take birth control or fertility medications. However, you can avoid smoking, which may make your eggs age faster (5).
The remaining follicles are what doctors call your ovarian reserve. As your ovarian reserve gradually gets smaller and smaller with age, the follicles that are left become less responsive to follicle-stimulating hormone (FSH). More FSH is needed for an egg to mature and ovulate than was necessary before. Eventually, the follicles don’t respond well enough to produce consistent ovulation, typically leading to long, irregular cycles that may be a sign of perimenopause (5).
At the same time, the quality of follicles worsens with age. Older follicles may contain either too many or too few chromosomes (5, 6, 7). This increases the chances that an embryo also will have too many or too few chromosomes and makes miscarriage more likely (6). Aging also increases a woman’s risk of disorders that may adversely affect fertility, such as uterine fibroids, endometriosis, and tubal disease (3).
However, it’s worth noting here that your age doesn’t predict whether your eggs are in good shape or not (6). Or, as ASRM notes, “Women with poor ovarian reserve have a lower chance of becoming pregnant than women with normal ovarian reserve in their same age group (5).”
Meaning: Each woman's egg reserve is unique to her. So while there is a documented interplay between a decline in ovarian reserve and age, it’s also possible to have a sufficiently healthy ovarian reserve in your 30s. (Side note: If you seek fertility assistance, one of the first tests a reproductive endocrinologist (a specialized OB/GYN) recommends is an evaluation of your ovarian reserve (6).)
Don't worry — getting pregnant in your 30s isn’t impossible. However, doing so may take a bit longer, according to a series of papers exploring age-related fertility and time to pregnancy (TTP).
One of the most interesting studies, published in Human Reproduction, investigated pregnancy rates among 782 couples who were using fertility awareness-based methods (FABMs) and had sex at peak fertility. Here’s what they found: Women between the ages of 35 and 39 had a slightly less than 30% chance of getting pregnant on their most fertile days (8).
These numbers should give you some hope, right? Plus, if you recall the statistics we mentioned earlier, from ASRM and from research, these numbers are superior.
The takeaway? Having sex on your most fertile days may be highly effective in helping you to achieve pregnancy in your 30s (or any age!) (8).
You may wonder how long it might take to get pregnant in your 30s. A paper in Fertility and Sterility answered this question in a TTP study of couples of different ages. They found that 58.4% of those over age 35 conceived within six months of trying (8).
You may have heard that up to one-third of cases of infertility may be due to male factors (9). With age, men’s testes become smaller and softer, producing less healthy sperm (5). According to a massive meta-analysis of 90 studies of 93,839 men, age negatively affected semen volume, movement, and the shape and size of sperm (10). For example, aging caused more sperm to have defects like bent or coiled tails in one study (11).
What all this means is it may take longer to get pregnant with an older male partner. One paper found that men over the age of 45 took five times longer to achieve pregnancy with their partners compared to men under the age of 25 — even after adjusting for the frequency of sex, women’s age, and lifestyle factors, such as drinking alcoholic or caffeinated beverages (4).
We've covered a lot of ground here. By now, it's hopefully clear that although getting pregnant in your 30s may not be as easy as it would've been in your 20s — it is doable.
Don’t beat yourself up about postponing your pregnancy plans until now — give yourself credit. You weren't ready to expand your family back then, and that's totally ok.
Now, you are. And cheers to that!
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