The 90-Day Preconception Window: How to Optimise Your Nutrition Before Trying to Conceive
The three months before you start trying to conceive are one of the most meaningful windows to act on nutrition. Eggs take approximately 90 days to complete their final stages of maturation, and sperm take a similar amount of time to develop. The nutritional environment during this period can influence egg quality, sperm quality, hormone balance, and how well the body is prepared for early pregnancy.
This is not about eating perfectly. It is about building a strong foundation before you need it. Here is what to focus on.
Blood glucose and insulin levels play a meaningful role in hormonal regulation and ovulation. When blood sugar is frequently spiking and dropping, this can place stress on the body's hormonal environment and affect cycle regularity. For those with PMOS or insulin resistance, this is particularly relevant, but blood sugar balance matters for everyone in the preconception period.
The goal is not to limit carbohydrates, but rather to opt for nutrient and fibre-rich sources and include them as part of a balanced meal to support steady blood glucose levels.
Eating regularly throughout the day and avoiding long gaps between meals is a simple but effective way to keep blood sugar stable.
The preconception period is a time to focus on what to add to the plate, rather than what to take away. Nutrient-dense foods provide the building blocks for reproductive health, hormone production, and early fetal development. A dietary pattern that emphasises vegetables, fruit, legumes, wholegrains, oily fish, eggs, nuts, and olive oil provides a broad range of vitamins, minerals, antioxidants, and anti-inflammatory compounds that collectively support fertility outcomes.1,2
No single food will make or break a preconception diet. The overall pattern across weeks and months is what matters. Thinking about variety across the week, rather than daily perfection, is a more useful frame.
A Mediterranean-style dietary pattern is one of the most well-researched in the context of fertility and has been associated with improved reproductive outcomes in multiple studies.1
Iron is directly involved in ovulatory function and is one of the most important nutrients to address before conception.2 Low iron stores, even without a formal diagnosis of anaemia, can affect ovulation and energy levels. Requirements increase significantly during pregnancy, which means entering pregnancy with depleted stores can quickly become a problem.
Getting your ferritin (iron storage) level checked before trying is worthwhile. A result that sits within the broad laboratory reference range may still be suboptimal for fertility and pregnancy. A registered dietitian can help interpret your result in context and provide targeted dietary and supplement guidance to bring levels up before conception.
Both dietary sources and supplement form matter. Haem iron from meat and fish is absorbed more readily, while non-haem iron from plant sources is enhanced by vitamin C eaten at the same meal. If supplementation is needed, the right form and dose depends on your individual levels and tolerance.
A prenatal supplement is recommended from at least one month before trying to conceive, but the 90-day window is an even better time to start. The most critical period for folate is in the very early weeks of pregnancy, often before someone knows they are pregnant, which is why starting well in advance matters.
Not all prenatal supplements are the same, and a generic off-the-shelf option will not be appropriate for everyone. A registered dietitian can assess whether your diet and current supplement are covering your needs, or whether there are gaps to fill. This might include additional vitamin D, a different form of folate, iron, DHA, or other nutrients depending on your individual dietary intake and bloodwork. Addressing any gaps before conception can be helpful, as nutritional demands increase significantly during pregnancy.
Even with a good diet, gaps are common. Deficiencies in key preconception nutrients are often asymptomatic and go undetected without specific testing. Vitamin D, iron, vitamin B12, iodine, and zinc are among the nutrients most frequently insufficient in women of reproductive age, and each plays a direct role in reproductive health.2,3
This is where working with a registered dietitian makes a real difference. Rather than guessing at supplements or following a generic preconception protocol, a dietitian can review your diet, interpret your bloodwork, and identify what actually needs attention for you individually. The 90-day window is the right time to do this. Acting early means there is time to correct gaps before they matter.
Ready to Use Your 90-Day Window Well?
Preconception nutrition is most effective when it is tailored to you. Nula Nutrition provides registered dietitian consultations for women preparing to conceive, including dietary review, bloodwork interpretation, supplement guidance, and a personalised plan for the preconception period. Available in Calgary and online across Alberta, including Canmore, Banff, Edmonton, and Cochrane.
Seeking evidence-based nutrition support in the lead-up to trying to conceive?
Book a Free Discovery CallNula Nutrition. Registered dietitian services for women's health. Calgary and online across Alberta.
Written by Madison Hows RD APD
References
1. Gaskins AJ, Chavarro JE. Diet and fertility: a review. American Journal of Obstetrics and Gynecology. 2018;218(4):379–389. PMID: 28844822
2. Shukla S, Shrivastava D. Nutritional deficiencies and subfertility: a comprehensive review of current evidence. Cureus. 2024;16(8):e66477. PMID: 39246987
3. Mashhadi F, et al. Nutritional interventions for enhancing female fertility: a comprehensive review of micronutrients and their impact. Nursing Research and Practice. 2025. PMC12343174
