Written by Jennifer Walpole. Reviewed by Dr Phoebe Howells. 

Jennifer Walpole is a BANT Registered Nutritionist specialising in Fertility and Pregnancy nutrition, supporting individuals and couples who are looking to optimise their fertility for conception, whether spontaneously or via IVF. Jen also works alongside Consultant Obstetricians and accredited specialists in Foetal and Maternal Medicine at Bliss - the Chelsea Clinic for Women & Children, consulting with parents for nutrition support throughout pregnancy.

The 90-Day Window Most People Overlook

As a Fertility Nutritionist, I recommend that people trying to conceive consider a 90-day or 3-month window to truly prepare for preconception or IVF. Although this may feel like a long time, there is science behind these timeframes - the egg and sperm don’t develop overnight. The 3 months before conception represent a critical biological window during which egg maturation and sperm development are highly sensitive to nutrition, oxidative stress, and lifestyle factors. Within this timeframe, we can not only optimise egg and sperm quality but also improve potential fertility and IVF outcomes.

Although as women we are born with all our eggs (known as follicles or oocytes), their maturation occurs over approximately 90 days before ovulation. During the final stages of this process, the female sex hormones work to recruit the most dominant follicle, which is then ovulated and (hopefully) fertilised. In contrast, semen is constantly being produced in the testes. Sperm production (known as spermatogenesis) takes approximately 64-74 days in its complete cycle, with a further 10-12 days for epididymal maturation before ejaculation. 

Whilst it’s widely accepted that embryo quality is determined by the quality of the egg and sperm, maternal and paternal health matters too, with recent research from animal studies highlighting that even the father’s health at the point of conception has an influence too. 

Lifestyle factors, including obesity, diet/nutrition, stress, toxins and endocrine disrupters, all impact egg maturation and spermatogenesis, leading to a decline seen in embryo quality. Although nutrition plays a foundational role here, there are often nutrient gaps that need to be filled through supplementation. Soil depletion, food quality, stress, and digestive function all contribute to increasing these needs. However, supplementation is not an overnight quick fix and needs to be taken consistently for cumulative effects. Therefore, for many reasons, it’s important to consider the 90-day window when preparing for pregnancy or fertility treatment.

Oxidative stress

Before we explore the 90-day window in more detail, let’s consider the role and impact of oxidative stress, which often comes up when discussing optimising fertility. 

Oxidative stress is caused by an excess of free radicals that, without the presence of enough antioxidants to mitigate them, can impact fertility. This is because egg and sperm cells are highly vulnerable to oxidative stress during the final maturation phase. Whilst oxidative stress is a normal biological process, excessive levels have been associated with aneuploidy risk, impacting IVF outcomes considerably. During the 90-day window for preconception preparation, common sources of oxidative stress to consider include: poor diet, environmental toxins such as plastics, pesticides, and forever chemicals, alcohol, smoking/vaping, excessive caffeine, over-exercising, and other factors such as stress, poor sleep, and blood sugar imbalances. Let’s dive into some of these.

Diet 

The inclusion of antioxidants in the diet is widely accepted as supporting fertility and mitigating damage caused by oxidative stress. For example, Vitamins A, C, E, Folate, Selenium, Zinc, CoQ10 and N-acetyl cysteine (NAC) have been shown to contribute to the protection of cells from oxidative stress. Although these nutrients can be obtained from eating a varied diet that includes protein, colourful fruits and vegetables and healthy fats, supplements targeted to support egg or sperm quality, such as OVUM’s Time to Conceive® For Women for egg health or OVUM’s Time to Conceive® For Men for sperm health, can certainly fill any nutrient gaps.

Plastics and pesticides

In addition to diet, recent research has highlighted a correlation between prolonged exposure to microplastics and reduced fertility. In fact, microplastics have been detected in follicular fluid and the testes. Research has also highlighted a link between pesticides, poorer semen parameters and higher DNA fragmentation, resulting in poorer sperm quality and chromosomal aneuploidy. Although this all sounds incredibly alarming, small, achievable swaps can make a big difference. For example, avoid reheating food in plastic (such as with ready meals or convenience foods), and swap plastic food storage for glass or stainless steel. To reduce pesticide exposure, you can consider switching to organic options with some of the fruits and vegetables that are the worst offenders for pesticide residues, known as the ‘dirty dozen’. 

Other causes

More obvious causes of oxidative stress include smoking, vaping and excessive alcohol and caffeine consumption. Whilst alcohol and caffeine may still be enjoyed in moderation, smoking and vaping should be ceased. 

However, there are also less talked about causes of oxidative stress, including chronic stress, poor sleep, over-exercising and even blood sugar instability, all of which should be considered when trying to conceive and seeking to optimise fertility and IVF outcomes.

The Science Behind the 90-day window

When it comes to this 90-day window, it can be helpful to understand the science behind egg maturation and spermatogenesis (sperm production), as well as the nutrient requirements for each stage.

The Science of Egg Maturation (Broken Down by Month)

Whilst women are born with all their eggs, it’s the final 90 days that determine mitochondrial competence, chromosomal integrity and cytoplasmic maturity. In simple terms, this is the period when the egg’s energy systems and genetic material are finalised. Let’s break this down month by month:

Month 1: Follicular Recruitment

During this time, a number of follicles are selected from the ovarian reserve or pool. Here, cells in the ovaries, known as granulosa cells that support oocyte (egg) growth and maturation, proliferate, and early mitochondrial activity increases. Nutrients involved in energy metabolism, antioxidant protection and hormonal signalling, including B vitamins, Vitamin D and trace minerals, support these underlying physiological processes as part of overall reproductive health. B Vitamins are required for energy metabolism (found in dark green leafy veg, meat, liver, fish and poultry), and Vitamin D is required for follicular signalling (found in optimal doses in OVUM’s Time to Conceive® For Women).

Month 2: Growth & Mitochondrial Expansion

During month two, the follicle grows, and mitochondrial activity increases, reflecting the rising energy demands of the developing oocyte. Mitochondrial function relies on nutrients involved in cellular energy metabolism and antioxidant defence. A nutrient that may help to facilitate this process is CoQ10, which is essential for ATP (energy) production. CoQ10 has been studied regarding oocyte quality, particularly in women with diminished ovarian reserve.

Month 3: Final Maturation & Ovulation

During the final month of maturation, leading to ovulation of the most dominant follicle, crucial processes involved in DNA synthesis occur, including chromosomal alignment and spindle formation. This stage is highly prone to oxidative stress, with a high demand for antioxidant nutrients, including Vitamin C and E, Selenium, and Zinc (all found in OVUM’s Time to Conceive® For Women). Other nutrients that might be important to consider here include those that support the egg cell membrane, such as Omega-3, which can be obtained from oily fish, algae oil, or supplementation. 

The Science of Spermatogenesis (Broken Down by Month)

Spermatogenesis is a complex process in which stem cells in the male testes develop into mature sperm, consisting of a sperm head, which carries 50% of the DNA of the future embryo, and a sperm tail, which aids motility and supports fertilisation of the oocyte. This process can be broken down into three phases:

Month 1: Early Cell Division (Spermatogonial Phase)

This is where stem cells divide and begin to differentiate. DNA replication begins, a process that is vulnerable to nutrient deficiencies and toxin exposure. Nutrients that support this process include Folate and B12 for their role in DNA synthesis and cell division, and Zinc for its role in cell replication (all found in OVUM’s Time to Conceive® For Men). Other nutrients to consider for supporting cell membrane integrity include Omega-3. 

Month 2: Cell Division Phase (Meiosis)

Spermatocytes then undergo two rounds of meiosis, a process of cell division during which accurate cell division and DNA integrity are central. During this process, key nutrients, including Zinc and Selenium, support antioxidant enzymes, and Selenium also contributes to normal spermatogenesis. CoQ10 supports mitochondrial function by enhancing energy production. 

Month 3: Final Maturation

In this final phase, spermatozoa are formed and acquire motility in the epididymis, where they are stored prior to ejaculation. This final stage is where there is the greatest potential for oxidative damage, increasing the need for antioxidant nutrients. For example, Vitamin C and E can help to protect cells from oxidative stress. N-Acetyl L-Cysteine is a precursor to glutathione (the body’s master antioxidant, which may also help to reduce damage from oxidative stress). Further to antioxidant support, CoQ10 during this final stage continues to support mitochondrial energy production.

Why 3 Months of Consistency Matters

As highlighted, egg maturation leading to ovulation and spermatogenesis are complex processes which require an array of nutrients, including antioxidants, at every stage. 

Nutrient sufficiency is cumulative, and it can take time to improve your status due to factors such as food quality, digestive function, stress, nutrient needs, and more. 

In addition, many of these processes are continuous and not a one-off event, therefore requiring a constant supply of nutrients. For example, methylation (the process by which we synthesise DNA) needs a continuous supply of nutrients, including Folate and B12, to work optimally. Further, antioxidant defences rely on sustained intake, especially when there is ongoing exposure to environmental toxins and other factors which increase oxidative stress. 

Therefore, it’s important to consider supplementing throughout the 90-day window to influence the cohort of eggs or sperm being developed. By supplementing consistently, you will ensure that you fill any nutrient gaps, as even balanced diets may not meet therapeutic levels due to soil depletion and those other factors mentioned. Furthermore, ensuring intake of bioavailable, well-researched forms (e.g., methylated Folate, active B vitamins, MicroActive® CoQ10) can help you meet these needs. Whilst you cannot change your genetics, you can influence the cellular environment, thereby improving egg, sperm, and therefore embryo quality. 

Key Takeaways

• There is a roughly 90-day window during which eggs mature, and sperm cells develop. Within this time, these cells are heavily influenced by their environment, offering an opportunity to optimise egg and sperm health.

• Oxidative stress is often discussed in fertility, being seen as an important influence on egg and sperm health, particularly during this 90-day window. Common sources of oxidative stress include environmental toxins, smoking and alcohol. Antioxidants, found in diets or supplements, play a role in protecting these cells against oxidative stress. 

• Consistency in optimal nutrient intake during egg and sperm development is important. This is because effects are cumulative, and many of the processes required in the development of these cells are ongoing, requiring nutrients throughout the 90-day window.