What Actually Affects Fertility in Your 40s
Most people assume fertility automatically declines with age, and that once you cross 40, the door begins to close. I want to challenge that assumption, because in my clinical experience, it is far more nuanced than that.
Yes, age matters. Ovarian reserve, egg quality, ovulation regularity, and miscarriage risk are all influenced by the biological clock. I will never minimize that reality for my patients. But many of the changes people automatically attribute to age are also being driven by inflammation, oxidative stress, poor sleep, nutrient depletion, insulin resistance, thyroid dysfunction, toxin exposure, and chronic stress. These are not inevitable features of aging. Many of them are addressable.
That is why fertility does not always follow a straight line.
In my practice, I have seen women in their 20s struggle to conceive because of PCOS, endometriosis, autoimmune conditions, smoking, poor diet, or metabolic dysfunction. I have also seen women in their 40s conceive naturally or respond beautifully to IVF once we identified and addressed the deeper drivers of their reproductive decline. I have helped the oldest woman in the United States conceive using her own eggs at age 51 through PRP ovarian rejuvenation and mini-IVF. Age is a factor, not a final verdict.
One of the most important conversations I have with patients over 40 centers on mitochondrial health. Mitochondria are the energy centers of the egg. When mitochondrial function declines, egg quality typically declines with it. Supporting that function is one of the most impactful things we can do for fertility after 40.
How to Improve Fertility Naturally After 40
My goal with every patient is never to pretend age does not matter. My goal is to identify and address the specific factors that are accelerating reproductive aging in that individual woman’s body.
The foundation of that work always starts with lifestyle:
- Better sleep, because hormonal repair happens during rest
- Blood sugar balance, because insulin resistance is one of the most underdiagnosed fertility disruptors I see
- Stress reduction, because chronic cortisol elevation directly suppresses reproductive hormones
- Regular movement that supports the body without overtaxing it
- Lower toxin exposure from plastics, pesticides, and environmental chemicals
- Adequate protein and healthy fats to support hormone production
On the topic of exercise, I want to be direct with my patients: more is not always better when it comes to fertility. Overtraining can actually work against you. For most of my patients over 40, walking, strength training, yoga, and practices that support the nervous system tend to be more beneficial than constant high-intensity exercise. We are trying to create an environment inside the body where reproduction feels safe.
Best Supplements for Fertility Over 40
CoQ10 is the supplement I discuss most frequently with patients who are focused on egg quality, because it directly supports mitochondrial energy production inside the egg. But CoQ10 is one piece of a much larger picture.
Other nutrients that may help support fertility after 40 include:
- PQQ, which supports mitochondrial biogenesis
- NAC, for antioxidant support and reducing oxidative stress
- NMN, for cellular energy and NAD+ production
- Alpha-lipoic acid
- Omega-3 fatty acids
- Magnesium
- Vitamin D
- Methylated folate
- Zinc
- Selenium
- Choline
For women who need more comprehensive, targeted support, Rejoova Eggs and Rejoova Repair were designed specifically to address mitochondrial decline, oxidative stress, inflammation, poor egg quality, and hormone imbalance together, not as isolated issues.
Fertility after 40 is not simply about fighting biology. It is about reducing the factors that accelerate reproductive aging and actively supporting the systems that help the body function at its best. When we do that work thoroughly and patiently, I consistently see what others told my patients was impossible.
Dr. Zaher Merhi is a Co-Founder of Rejoova and the founder of Rejuvenating Fertility Center, with locations in Manhattan, Connecticut, Long Island, Westchester, and Brooklyn. He specializes in less-invasive IVF, ovarian rejuvenation, and personalized fertility care for women of all ages.