The Unborn Child Develops So Rapidly!

In the following few paragraphs I've highlighted some of the ways the child's body develops, with an emphasis on the early stages of pregnancy - often on a day-by-day basis. The developments I've chosen are only a few of the hundreds of other things that are happening early in pregnancy. I selected them because they captured my imagination. Readers who browse through the appendices will find information about other developments they may find interesting.

But before we begin, a comment might be in order about the moment when it all gets started. A new human being is conceived when a sperm fertilizes an egg. The sperm has 23 chromosomes and so does the egg. But the fertilized egg has 46, half from each parent, and is genetically unique. These 46 chromosomes, which are fixed at conception, establish the child's sex and are a blueprint for how it will develop, both during pregnancy and after birth.

Although the child begins developing immediately after conception, the most visible advances occur during the third to eighth weeks. In fact, key organs are already developing in the third week - a time when many women are just beginning to wonder if they are pregnant.

Blood vessels start to form very early, about 13-18 days after fertilization. Then, on about the 20th day - nearly the end of the third week - the foundation of the brain, the spinal cord, and the entire nervous system is established.

The eyes begin to develop early in the fourth week after conception. During this extremely critical week the esophagus, gallbladder, liver, lungs, pancreas, pharynx, stomach, and trachea also begin to form. And, toward the end of the week, the nose, tongue, and spleen also start to develop.

The heart begins to beat on about the 22nd day after conception, circulating blood throughout the child. The arms begin to form on about day 26, followed by the beginnings of the legs on day 28, the same day that the mouth opens for the first time. Also on the 28th day, building blocks are present for 40 pairs of muscles that will run from the base of the skull to the bottom of the spinal column.

The kidneys begin to develop early in the fifth week after conception. The jaws and ears are also forming during this week and the face starts to look human.

The intestines are defined at the end of the first month, and the larynx is developing on about the 32nd day, the same time that spinal nerves begin to sprout and the palate is forming.

The cerebral cortex, the part of the brain that controls the intellect and motor activity, begins to differentiate on the 33rd day after conception, the same day that the forearms and shoulders can be distinguished. The elbows are developing on the 34th day, as are both hand and foot plates.

The olfactory nerve, which is related to the sense of smell, is present in the brain on the 35th day after conception, the day when the ribs begin to form and lengthen.

Both the upper and lower lips are forming early in the sixth week after conception. Also during the sixth week the eye is obvious, reflecting the fact that retinal pigment is already present. The beginnings of the eyelids and the fingers are also forming during the sixth week, the testes become identifiable at this time and some salivary glands appear. By the sixth to seventh weeks after conception, the heart is contracting forty to eighty times each minute.

The aorta is developing on the 36th day after conception, and all the muscle blocks have appeared. The feet and the thighs become distinct on the 37th day. Finger rays are visible on the 38th day, when the nose is also formed. The urinary bladder is developing on the 39th day, and on the 40th day, the forehead, nostrils, diaphragm and teeth are beginning to appear.

The penis begins to develop on about the 42nd day after conception, the same day that the beginnings of the toes are evident.

Both the eyes and ears are developing rapidly during the seventh week after conception. At this time, the thumbs, neck, heels of the feet and all of the fingers are also present.

Nipples and the first hair follicles appear on the 44th day after conception. On the 46th day, microscopic examination can identify the child's sex because the ovaries and testes have differentiated.

The cheeks are visible on about the 47th day, when the knees are also developing. The vagina forms during the 36th to the 49th days, while the wrist is developing on about day 48. During the 49th to 51st days after conception, the arms are longer and bent at the elbows.

Taste buds begin to form during the eighth week after conception. All parts of the limbs are apparent at this time. In addition, the fingers and toes have lengthened and are completely separated.

On the 50th day after conception the eyes are heavily pigmented and the nose looks stubby. The ankles are present on the 54th day and the major blood vessels of the body take on their final scheme.

On the 56th day, the fingers of both hands are usually found close to the nose, the muscles of the stomach, esophagus, and intestines begin to proliferate, and the face appears quite human. All parts of the arms and legs are well developed, including the toes. The primary teeth are at the cap stage.

By the end of the eighth week the overwhelming majority (several thousand) of the body's organs, structures and systems have already begun to develop. Few, if any, new structures begin to form after this time. During the remainder of the pregnancy, development consists mainly of growth and maturation of the parts of the body that are already present.

Key changes that do occur past the eighth week, however, include the appearance of hair follicles on the eyebrows, eyelids, upper lip and chin at the end of the second month. In addition, fingernails and toenails begin to develop about the tenth week after conception and scattered rudiments of hair also form at this time. External genitalia start to appear at the end of this week which will indicate to the naked eye whether the child is a boy or a girl.

During the fourth month, fine palm lines have formed that can be used to permanently identify the child. Finger, palm and footprints are never duplicated among individuals.