Your partner is fertile… and you are too. So why is it not happening?

Understanding unexplained infertility: between science, complexity, and hope

What is fertility?

Fertility is the biological capacity of a couple to conceive a child. It depends on a finely coordinated sequence of events: a good-quality ovulation, functional and motile sperm, fertilization at the right time, embryo transport through the fallopian tube, successful implantation, and a receptive hormonal and immune environment.

Even under optimal conditions, the chance of pregnancy per cycle is only around 20–25%. This already highlights that human reproduction is a fragile and probabilistic process rather than a guaranteed one.

When do we speak of infertility?

Infertility is defined as the absence of pregnancy after 12 months of regular unprotected intercourse (or 6 months if the woman is over 35 years old).

In most cases, a clear cause is identified (ovulatory, tubal, sperm-related, or uterine factors). However, in about 15–30% of couples, all standard investigations remain normal. This is referred to as unexplained infertility.

Unexplained infertility: a frequent reality

In these cases, standard assessments show:

• normal ovulation

• patent fallopian tubes

• normal uterine cavity

• normal semen analysis

Yet pregnancy does not occur.

This does not mean there is “no cause,” but rather that current medical tools are not yet able to detect all relevant biological mechanisms.

What medicine does not fully measure yet

Human reproduction depends on very subtle processes:

• Subtle gamete quality issues that are not visible on standard tests

• Oxidative stress, which can affect DNA integrity in sperm and oocytes

• A very narrow implantation window in the endometrium

• The materno-embryonic immune dialogue, essential for tolerance

• Low-grade chronic inflammation, sometimes associated with minimal endometriosis or metabolic factors

A significant proportion of cases remain biologically “invisible” with current diagnostic tools.

What is required for a pregnancy to occur

Pregnancy requires perfect synchronisation:

1. Ovulation at the right time

2. Viable sperm present in the reproductive tract

3. Fertilisation

4. Normal early embryo development

5. Efficient tubal transport

6. A receptive endometrium

7. Immune tolerance of the embryo

A small imbalance at any stage may prevent conception.

The role of psychological factors

Stress is not a direct cause of infertility, but it can act as a biological modulator. It may influence hormonal regulation, ovulation, sleep quality, libido, and the overall hypothalamic–pituitary axis.

It is therefore best understood as a contributing factor rather than a primary cause.

What can be done in practice?

Even when all investigations are normal, several modifiable factors can improve fertility potential.

Body weight plays an important role. Both underweight and overweight states can disrupt hormonal balance and ovulatory function. Excess weight is also associated with chronic low-grade inflammation and reduced oocyte quality, even when standard tests remain normal.

Nutrition is another key element. A diet rich in antioxidants—molecules that protect cells from oxidative damage—may support reproductive health. These include vitamins and plant compounds found in berries, citrus fruits, leafy green vegetables, carrots, tomatoes, nuts, and seeds.

Omega-3 fatty acids (found in fatty fish such as salmon, sardines, and mackerel, as well as flaxseeds, chia seeds, and walnuts) are known to support anti-inflammatory pathways and may contribute to a healthier reproductive environment.

Moderate physical activity—around 150 minutes per week such as brisk walking, swimming, cycling, or dancing—supports metabolic and hormonal balance. However, excessive intense exercise may negatively affect ovulation.

Lifestyle factors are equally important: smoking has a clear negative effect on ovarian reserve and gamete quality, alcohol and environmental toxins can disrupt hormonal function, and sleep quality directly influences endocrine regulation.

When everything is normal

This is often the most difficult situation emotionally: all tests are reassuring, yet pregnancy does not occur.

In such cases, it is important to remember that human fertility is inherently probabilistic, even in perfect health. Time, combined with optimised conditions, often plays a role.

Medical support or assisted reproductive techniques may be discussed depending on age, duration, and individual context.

Conclusion

Unexplained infertility does not mean there is no explanation—it often reflects the current limits of medical knowledge in capturing extremely subtle biological interactions.

It also does not mean hopelessness. In many couples, conception still occurs naturally over time, especially when modifiable factors are addressed.

I am aware that this journey can be emotionally demanding and full of uncertainty. Please know that I am here to accompany you through it, to guide you step by step, and to adjust the approach according to your situation and your needs.

With warm regards,I remain at your disposal throughout this process.

Cordialement,

Dr. Sandra Yene Amougui