The first 1,000 days: a defining period for life

Nine months of pregnancy, followed by the first two years of life: the period known as the first 1,000 days is now recognised as one of the most defining of an entire lifetime. What a baby eats, what they feel, what they experience in contact with their parents — all of this leaves deep and lasting impressions, well beyond childhood.

But what actually happens during these 1,000 days? What are the key issues for your child’s health and development? And how, as parents, can you navigate this period with the right guidance and support? Mi&Ma offers you a comprehensive, accessible overview to help you approach these early days with a clear and calm mind.

What exactly are the first 1,000 days?

From conception to a child’s second birthday

The first 1,000 days begin at conception and end on a child’s second birthday. This period therefore covers nine months of pregnancy — approximately 270 days — and the first 730 days of a baby’s life. The definition was established by the World Health Organization (WHO) and has since been adopted by many governments to make their public health and perinatal policy evolve.

As an example, in France, the national First 1,000 Days programme, launched by the ministries responsible for health and early childhood, draws on a landmark report submitted in 2020 by an expert commission led by neuropsychiatrist Boris Cyrulnik^[1]. The goal: to make this period a priority for prevention and family support, by bringing together all those involved in the care pathway — from maternity units to Maternal and Child Health centers (PMI) and local healthcare professionals^[1].

Why is this period so foundational?

The reason the first 1,000 days attract such close attention is straightforward: science is clear on this point. Never does the human brain develop as rapidly^[1], and never does the environment have as great an impact on that development^[1], as during this window of life. The experiences a fetus goes through, and then a newborn, have a lasting influence on physical health, cognitive and emotional abilities — and even on health in adulthood.

This is not about putting pressure on parents or striving for perfection. It is simply an acknowledgement that the care, nutrition, quality of emotional bonding and security of the environment in the very earliest days of life lay solid foundations — for the child of today, and the adult of tomorrow^[1].

What happens to a baby during the first 1,000 days?

Remarkable development, week by week

From the very first weeks of pregnancy, a baby’s body and brain develop at a breathtaking pace. The nervous system takes shape, organs form, and the senses gradually awaken^[2]. By the time of birth, a newborn’s brain already contains billions of neurons, and the connections between them multiply at a rate unmatched at any other point in life.

After birth, this early development continues just as rapidly^[2]. Baby learns to recognize voices, faces and smells. They explore their environment, develop their motor skills, and begin to communicate long before uttering their first words. Every interaction, every moment of care, every shared experience with their parents feeds this development and helps build the foundations of their emotional and social life^[2].

Nutrition: a cornerstone from the very start

Among all the factors that influence a baby’s development during the first 1,000 days, nutrition holds a central place. From pregnancy onwards, what a mother eats has a direct impact on the fetus’ growth and the build-up of their nutritional reserves.

After birth, breast milk — when possible and desired — provides nutritional intake perfectly suited to a newborn’s needs, alongside its many benefits for the immune system^[3]. When breastfeeding is not possible, infant formula is a safe and appropriate alternative, formulated to meet the specific needs of each stage of a baby’s development.^[3] Then comes the introduction of solid foods, generally around 6 months, which marks a new milestone for both the child and the family.

Emotional bonding and environment matter just as much as nutrition

The first 1,000 days are not played out in the feeding alone. The quality of the relationship between parents and their child is equally important for their development^[4]. What specialists refer to as attachment — the sense of security a baby builds through close contact with their caregivers — is formed precisely during this period and has a profound and lasting influence on a child’s emotional wellbeing.

A stable, caring and reassuring environment is therefore a form of care in its own right. This does not mean being “perfect” parents — no such thing exists — but simply being present, attentive and responsive to a baby’s needs^[4]. And for parents going through difficult times, such as postnatal blues or a period of exhaustion, recognizing these signs and seeking support is a fully valid part of the journey.

And for parents — what does this period look like?

From pregnancy to coming home

The first 1,000 days are an intense time for parents, just as much as for their baby. It all begins well before the birth: prenatal appointments, birth preparation, prenatal interviews — all of these are opportunities to anticipate the arrival of a child and to voice questions, doubts and expectations.

Then comes the birth, the stay in the maternity unit, and the return home. Broken nights, new responsibilities, the profound shift in identity that comes with becoming a parent: all of this can weigh on you, even when everything is going well^[5]. Postnatal blues, experienced by one in five new mothers in the days following birth, is a common illustration of this. It should neither be dismissed nor be a source of guilt: talking to a healthcare professional is always the right step^[5].

Who can you turn to for support?

The good news is that parents are not alone. In many countries, there are services, professionals, and resources available to support families throughout a child’s early years.

Depending on where you live, this support may be provided by a range of professionals, such as maternal and child health services, midwives, pediatricians, general practitioners, or local family support organizations. These professionals offer regular follow-up, personalized advice, and guidance from pregnancy through the child’s first years.

At the same time, more and more resources are available to help parents in their daily lives: reliable websites, educational materials, helplines, and mobile apps. These tools provide practical advice, clear guidance, and help families find professionals or services close to home.

Getting informed and building a support network from the very beginning can make this period more reassuring, with guidance tailored to both the parents’ and the child’s needs.

The first 1,000 days of your child’s life are an intense time — sometimes turbulent, but also full of discovery. From conception to your baby’s second birthday, every day matters, every moment of care matters, every shared experience matters.

Because every baby is unique, and every parenting journey deserves to be supported with gentleness, expertise and warmth, Mi&Ma is committed by your side. Because little moments deserve big care.

Sources:

[1] French Ministry of Health, Families, Autonomy and Disabled People. The First 1,000 Days — What Is It?

[2] 1000 premiers jours, Baby’s Development Milestones

[3] 1000 premiers jours, Feeding from 0 to 4 Months: Milk and Milk Alone

[4] mpedia, The Foundations of Baby Attachment: Building a Sense of Emotional Security

[5] 1000 premiers jours, Baby Blues and Postnatal Depression