Human Development

Resource HD-001

Human Development Before Birth

Working Draft 1.0
Section: Human Development
Last Updated: July 2026

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Figure HD-001-001. Every human life begins with an extraordinary journey. During pregnancy, a mother's body nurtures and protects her developing child as he or she grows from a single fertilised cell into a newborn baby.

Introduction

Every person has a beginning.

Before we speak our first words, take our first steps or celebrate our first birthday, an extraordinary process of growth and development has already taken place. Within the safety of the womb, a new human being develops from a single living cell into a baby with a beating heart, functioning organs, unique fingerprints and an individual genetic identity.

For most of human history, this remarkable journey remained hidden from view. Today, advances in embryology, genetics, ultrasound imaging and neonatal medicine allow us to observe human development with unprecedented clarity. Parents can watch their unborn child move during pregnancy, doctors can diagnose and sometimes treat medical conditions before birth, and scientists continue to deepen our understanding of the earliest stages of human life.

This Resource explains the major stages of human development before birth in clear, accessible language. It is based on recognised scientific knowledge and established medical understanding, while reflecting the belief of Right to Life New Zealand that every human life possesses inherent dignity and worth.

Whether you are a student, teacher, parent, healthcare professional or simply someone wishing to learn more about the beginning of human life, we hope this Resource provides a reliable and informative guide to one of nature's most remarkable journeys.

Chapter 1

A Remarkable Journey

Every human being shares a common beginning.

Although each of us is unique, every person who has ever lived has travelled the same remarkable path. Before birth, each of us developed within our mother's womb through an orderly and continuous process of growth that transformed a single microscopic cell into a fully formed baby.

Human development is one of the most remarkable processes found in nature. Guided by the information contained within our DNA, trillions of cells grow, divide and become specialised to form the tissues, organs and body systems that enable the human body to function. This development follows a carefully coordinated sequence that begins at fertilisation and continues throughout pregnancy, birth, childhood and adult life.

Scientists divide human development into stages to help describe the many changes that occur before birth. These stages are useful for study and communication, but they do not represent different kinds of human life. Rather, they describe successive phases in the life of the same developing human being.

The earliest stage begins when a sperm cell from the father and an egg cell from the mother unite during fertilisation. This produces a new living human organism known as a zygote. Although microscopic in size, the zygote possesses its own unique genetic identity. The DNA inherited from both parents determines many of the characteristics that make every individual unique, including biological sex, eye colour and countless other inherited traits.

During the following weeks, the developing child undergoes extraordinary change. Cells multiply rapidly and begin organising into specialised tissues and organs. The nervous system starts to form, the heart begins developing and later starts beating, and the foundations of every major body system are established. By the end of the embryonic period, the basic structure of the human body is already recognisable.

As pregnancy continues, growth and development accelerate. During the fetal period, organs mature, movements become stronger and more coordinated, and the baby responds increasingly to the surrounding environment. Throughout this process, the developing child remains the same individual, continuing the journey that began at fertilisation.

Modern medicine has transformed our understanding of life before birth. Ultrasound imaging allows parents and healthcare professionals to observe growth, movement and heartbeat throughout pregnancy. Three-dimensional and four-dimensional imaging provide detailed views of the developing baby, while advances in fetal medicine now enable doctors, in carefully selected cases, to diagnose and even treat certain medical conditions before birth.

Scientific discoveries over recent decades have greatly expanded our understanding of prenatal development. They have also reinforced an important biological principle: human development is a continuous process. The newborn infant, the child, the teenager and the adult are not different beings but different stages in the life of the same individual.

As Right to Life New Zealand, we believe that learning about human development encourages a deeper appreciation of the dignity and value of every member of the human family. While people may reach different ethical or philosophical conclusions, the scientific study of human development provides a shared foundation for informed discussion. We hope this Resource will encourage curiosity, deepen understanding and foster respect for the remarkable journey that every human being has undertaken.

Key Facts

• Every human being begins life through the process of fertilisation.

• Human development is continuous from fertilisation through birth and beyond.

• Each developing child has a unique genetic identity.

• The terms zygote, embryo and fetus describe recognised stages of prenatal development.

• The foundations of all major organs and body systems are established during early development.

• Modern medical technology allows many stages of human development to be observed before birth.