WEEK TEN

My Baby - WEEK TEN

The embryo reaches a developmental milestone at the end of this week--it has achieved its basic structural form, and will be known as a fetus (Latin for "offspring") from now until it reaches full term. Because the fetus is still curled up in a snug position in the uterus, it's hard to measure an exact length including the legs. For this reason, health professionals use the crown-to-rump measurement, or the distance from the top of the head to the buttocks. Your baby's crown-to-rump length is now about 1 1/4 inches, and she weighs less than half an ounce

WEEK NINE

My Baby - WEEK NINE

By now, your baby is being nourished through the placenta, a flat, spongy organ covered with wavy masses of capillary-filled tissue called chorionic villi. Nutrients pass through this tissue to the embryo, while wastes are carried away. The placenta and chorionic villi are made up of the same genetic material as the baby, and can offer important information about birth defects such as Down syndrome, Tay-Sachs disease, and cystic fibrosis.

WEEK EIGHT

My Baby - WEEK EIGHT

Go, baby, go! Your talented child has doubled in size in the past two weeks, and is now approximately three-quarters of an inch long. Body parts that formed in the first few weeks are growing more complex and specialized, including the eyes, limbs, mouth, heart, and brain. Fingers and toes are taking shape, along with the palate and pituitary gland. The eyelids are also forming--until they're complete, the eyes appear open.

WEEK SEVEN

My Baby - WEEK SEVEN

Although she still resembles a tiny alien, your baby's facial features are starting to form. Arms, legs, hands, and feet are taking shape, although they don't yet have fingers and toes. The brain is growing more complex; if you looked through a microscope, it would be clearly visible through the transparent skull. The embryo has started to move in small jerks, although you won't feel these until the fourth month.

WEEK SIX

My Baby - WEEK SIX

A wonderful new sound enters the world this week: your baby's heartbeat. Although still too faint to be picked up by a doctor's stethoscope, it's visible in a sonogram as a tiny, pulsing dot in the middle of your still-transparent embryo's body. From now until birth, it will beat approximately 150 times a minute, twice the average adult heart rate. The rest of the embryo is working hard, too--it will triple in size this week, to about a quarter of an inch long.

WEEK FIVE

My Baby - WEEK FIVE

Already a busy little bee, your developing embryo now has three layers. The outer layer, or ectoderm, will develop into the nervous system, while the endoderm, or inner layer, will become the liver, pancreas, intestines, and bladder. This week, the mesoderm, or middle layer, is developing into the heart and circulatory system, which will be the first organs to function. In the weeks to come, the mesoderm will also form the bones, muscles, kidneys and reproductive organs.

WEEK FOUR

My Baby - WEEK FOUR

By two weeks after conception, the ball of cells implanted in the lining of your uterus has divided into two parts.

One half will become the placenta, which nourishes your baby as she grows. The second half is the embryo itself. Around this time, nerve growth begins, as a sheet of cells folds backward to create the neural tube, or spinal column.

WEEK THREE

My Baby - WEEK THREE

Amazingly, your baby's genetic code was written at the moment of conception; his or her sex and all inherited characteristics--including eye color, hair, skin, and body type--have already been determin

ed. This week the ball of cells, or embryo, completes its journey through the fallopian tube and comes to rest in your uterus, a process known as implantation. You may experience light bleeding when the egg implants, which many women mistake for menstruation. In fact, spotting that is lighter than your usual menstrual flow is one of eight signs you may be pregnant.

WEEK TWO

My Baby - WEEK TWO

The journey toward birth begins with the release of an egg, an event known as ovulation. About halfway th

rou

gh the menstrual cycle, a ripened egg, or ovum, bursts from the ovary and is swept

into a fallopian tube, where it will be met by sperm who have completed the 6- to 9-inch journey through the cervix. Although millions of sperm typically start this trek, less than a thousand arrive; of these, only one will penetrate the egg to unite the male and female DNA at the moment of conception.

A word about multiples: There are two types of multiples, fraternal and identical. Fraternal twins (or triplets or quads) are the result of more than one egg being released at the same time, and each being fertilized. Identical twins occur when a single egg is penetrated by a single sperm, and then the fertilized egg splits into two genetically identical parts.

WEEK ONE

My Baby - WEEK ONE

When does pregnancy begin? Unless you're using ART (Assisted Reproductive Technology), it's impossible to know the exact moment of conception. For this reason, most health-care providers count 40 weeks from the date of your last menstrual period, or LMP, to calculate your due date. According to this method, pregnancy actually begins about two weeks before the sperm penetrates the egg. The baby's gestational age corresponds to the actual date of conception.