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What are the first thousand days?

Updated: May 11, 2023

When it comes to pregnancy and fertility, you may have heard of the term “the first thousand days”, but what does this mean? The first thousand days refers to the time from pre-conception (3 months prior to conception) until a baby is two years old. This time frame is highlighted to be one of the most important stages of a baby’s development as most of the genetic programming occurs at this time.

Conception phase

Genetic programming involves the creation of genetic material in the sperm and the egg. As women cannot make new eggs, the quality of the egg can be impacted by a range of factors including pollution, medical conditions and nutrition. These factors may cause inflammation around the egg or in our reproductive system (and can therefore damage genetic material), contribute to ovulation dysfunction, reduce uterine lining thickness or impact various hormones that are needed to regulate the conception and pregnancy phases. As for sperm, the same factors above can influence the quality AND quantity of sperm which can reduce the chances of implantation during conception and damage the genetic material of sperm.

Pregnancy and breastfeeding

During pregnancy, your baby’s genetics are still being programmed. Anything you are exposed to, so is bub, especially when it comes to nutrition! Think of your baby’s genes (genetic material) as light switches. Depending on what the genes are exposed to, they may switch on or off. The switching on or off a gene can contribute to certain characteristics or behaviours the baby may have when they’re older. Some important things we can influence with nutrition particularly, are allergies and food preferences.

Studies show that what a mum eats during pregnancy and breastfeeding can influence your baby’s food preferences and risk of developing a food allergy. A baby starts to develop their tastebuds around 4 months gestation so if you have a sweet tooth during pregnancy, your baby may also have one too! As for allergies, these are strongly genetic based. Let’s say, if mum or dad, or both mum and dad have food allergies, the baby is at higher risk of developing a food allergy than if neither mum nor dad has an allergy. However, if you’re able to have food allergens (or some) during pregnancy, this reduces the risk of your baby having a food allergy. The risk is further reduced when you introduce allergen-containing foods to your baby between 4-6 months of age.

Milestones and behaviours

The first thousand days also involve some major behavioural changes that may set up your baby for life. As some behaviours may be genetic (genetic disorders or conditions), others can be learned. This may involve chewing, walking, expressing emotions and/or talking. These often are achieved during the first 2 years of your baby’s life as this is the time when their brain is constantly learning and experiencing new behaviours, a lot more easily.

How can I optimise my baby’s nutrition during the first thousand days?

Seeing a dietitian like myself, with knowledge in fertility and pregnancy nutrition may be a good start to set your mind at ease and be with you for the entire process! You may also like to consider the following:

1. Prior to conceiving, complete a blood test to see your nutritional adequacy.

2. Ensure you are on top of your own health and have any health conditions well-controlled.

3. Eat a wide variety of food from the 5 food groups.

4. Ensure you have your medical support team which may include your GP, midwife, gynaecologist and dietitian through the entire process.


3. Early Life Nutrition Alliance

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