How Are Babies Made? (Ages 7-9)

Ages 3-5 Simple Explanation

You know how every living thing -- like puppies, kittens, and flowers -- has to start from something really small? Babies start small too! A baby begins when a tiny, tiny piece from a mommy and a tiny, tiny piece from a daddy come together inside the mommy's body.

You know how a puzzle needs all its pieces to make a picture? The piece from the mommy is called an egg, and the piece from the daddy is called a sperm. When they fit together, they make the very beginning of a baby! It is so tiny you cannot even see it without a special tool.

You know how a seed needs water and sunshine to grow into a plant? The tiny baby needs the mommy's body to give it food and keep it warm. There is a special, cozy spot inside the mommy called the uterus where the baby grows for nine whole months.

You know how you blow up a balloon and it gets bigger and bigger? The mommy's tummy gets bigger and bigger too as the baby grows! When the baby is finally ready, it comes out and the family gets to see and hold it for the very first time.

Ages 6-8 More Detail

Every new baby starts from two very important cells. The mother's body makes egg cells inside organs called ovaries, and the father's body makes sperm cells. These cells are much too small to see without a microscope. When one sperm cell reaches an egg cell and they join together, it is called fertilization -- and that is the moment a new baby starts.

The fertilized egg contains something called DNA, which is like a recipe book for building the baby. Half of the DNA comes from the mother and half from the father. That is why kids often look a bit like both of their parents! The DNA decides things like hair color, eye color, and even whether the baby will have dimples.

After fertilization, the tiny cell begins dividing -- one cell becomes two, two become four, four become eight, and so on. This growing ball of cells travels to the mother's uterus, which is a pear-shaped organ in her lower belly. The cells attach to the wall of the uterus and keep growing. At this stage, the growing baby is called an embryo.

Over the next few months, the embryo develops all its major body parts. A heart starts beating within just a few weeks. Arms and legs start to grow. Tiny fingers and toes appear. By about eight weeks, all the main body parts are forming, and the embryo is now called a fetus.

The fetus keeps growing for the rest of the nine months. It is connected to the mother through the placenta and umbilical cord, which deliver food and oxygen from the mother's blood. The baby floats in a warm, protective fluid and gets bigger and stronger every day.

When the baby is fully developed and ready, the mother's body goes into labor. Muscles in the uterus squeeze to help push the baby out through the birth canal, or sometimes a doctor delivers the baby through a C-section. Either way, a brand new person enters the world!

Ages 9-12 Full Explanation

Making a baby is a process called reproduction, and it starts with two cells. The mother's body has two small organs called ovaries that store and release egg cells. About once a month, one ovary releases a ripe egg cell -- this is called ovulation. The egg travels into a tube called the fallopian tube. Meanwhile, the father's body produces millions of tiny sperm cells. If a sperm cell meets the egg in the fallopian tube, the two cells can fuse together in a process called fertilization.

The moment fertilization happens, the combined cell (called a zygote) contains a full set of DNA -- half from each parent. DNA is like a detailed blueprint that will guide how the baby develops. It determines physical traits like eye color, hair texture, and body type. The zygote immediately begins dividing, becoming 2 cells, then 4, then 8, and so on, as it moves down the fallopian tube toward the uterus.

When the ball of cells reaches the uterus, it burrows into the thick, nutrient-rich lining. This step is called implantation. Once implanted, the cells keep dividing and start organizing into different types -- some will become brain cells, some will become heart cells, and some will become bone and muscle. By about eight weeks, all the major organs and body structures have started to form. At this point, the developing baby is called a fetus.

For the remaining months of pregnancy, the fetus grows and matures. It is nourished by the placenta, an organ that forms on the wall of the uterus and connects to the baby through the umbilical cord. The placenta filters nutrients and oxygen from the mother's blood and passes them to the baby. The baby is surrounded by a fluid-filled sac that acts like a cushion, protecting it from bumps and jolts.

By the end of the nine months, the baby is typically about 19 to 21 inches long and weighs around 6 to 9 pounds. Its lungs are ready to breathe air, its digestive system is ready to process milk, and its senses are developed enough to see light, hear sounds, and feel touch. The mother goes into labor when her body signals that the baby is ready to be born, and the baby enters the world ready to start life on the outside.