Our first nine months of life are the most eventful we will ever experience. Here are the major milestones of that life before birth - the first chapter in your own biography:
CONCEPTION: The father's sperm penetrates the mother's egg cell. Genetic instructions from both parents interact to begin a new and unique individual no bigger than a grain of sugar.
1ST DAY: The first cell divides into two, the two into four, and so on.
5 - 9 DAYS: The new individual burrows into the wall of the womb.
14 DAYS: The mother's menstrual period is suppressed by a hormone produced by her child.
18 DAYS: The heart is forming. Soon, eyes start to develop.
20 DAYS: The foundations of brain, spinal cord, and nervous system are laid.
24 DAYS: The heart begins to beat.
28 DAYS: Muscles are developing along the future spine. Arms and legs are budding.
30 DAYS: The child has grown 10,000 times its original size to 1/4 inch long. The brain has human proportions. Blood flows in the baby's veins but stays separate from the mother's blood.
35 DAYS: The pituitary gland in the brain is forming. The mouth, ears, and nose are taking shape.
42 DAYS: The skeleton is formed. The brain coordinates the movement of muscles and organs. Reflex responses have begun. The penis is forming in boys. The mother now misses her second period.
43 DAYS: Brain waves can now be recorded.
45 DAYS: Spontaneous movements have begun. Buds of milk teeth have appeared.
7 WEEKS: Lips are sensitive to touch. Ears may resemble family patterns.
8 WEEKS: The child is well-proportioned. Now a small-scale baby 1 1/8 inches and weighing 1/30th ounce. Every organ is present. The heart beats steadily. The stomach produces digestive juices. The kidneys begin to function. Taste buds are forming.
8 1/2 WEEKS: Fingerprints are being engraved. Eyelids and palms of hands are sensitive to touch.
9 WEEKS: The child will bend fingers around an object placed in the palm. Thumb sucking occurs. Fingernails are now forming.
10 WEEKS: The body is sensitive to touch. The child squints, swallows, wrinkles up brow, and frowns.
11 WEEKS: The baby urinates, makes complex facial expressions, even smiles.
12 WEEKS: The baby's vigorous activity shows distinct individuality. The child can kick, turn feet, curl and fan toes, make a fist, move thumbs, bend wrists, turn the head, open the mouth, and press lips together. Breathing is practiced.
13 WEEKS: The face is prettier. Facial expressions resemble the parents. Movements are graceful, reflexes vigorous. Vocal chords are formed, but without air the baby cannot cry. Sex organs are apparent.
4 MONTHS: The child can grasp with hands, swim, and turn somersaults.
4 - 5 MONTHS: The mother first feels the baby's movements.
5 MONTHS: Sleeping habits appear. A slammed door will provoke activity. The child responds to sounds in frequencies too high or low for adults to hear.
6 MONTHS: Fine hair grows on eyebrows and head. Eyelash fringe appears. Weight is about 22 ounces, height 9 inches. Babies born at this age have survived.
7 MONTHS: Eye teeth are present. Eyelids open and close. Eyes look around. Hands grip strongly. Mother's voice is heard and recognized.
8 MONTHS: Weight increases by over 2 pounds and baby's surroundings get cramped.
9 MONTHS: The child triggers labor and birth occurs, usually 255 - 275 days after conception. Of 45 generations of cell divisions before adulthood, 41 have taken place. Four more will come during the rest of childhood and adolescence.
And not until the baby has gone through all these events on the inside do we see the new child on the outside.
NOTE: The milestones listed above have been documented by scientific research. Slight variations of hours and days may exist, and future research may show that some milestones occur earlier than is now known.