For the first eight weeks, your developing baby is called an embryo. Tiny limb buds that will grow into arms and legs appear. The embryo looks like a tadpole. Heart and lungs are beginning to form. By the 25th day, the heart starts to beat. The neural tube that becomes the brain and spinal cord begins to form. By the end of the first month, the embryo is about a half inch long and weighs less than one ounce.

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All major body organs and systems are formed but not completely developed. The placenta, which exchanges nutrients from your body for waste products processed by the baby, is visible in its early stages of working. Ears, ankles and wrists are formed. Eyelids form and grow but are sealed shut. Fingers and toes are developed. By the end of the second month, the fetus looks more like a person than a tadpole, is about one inch long and still weighs less than one ounce.

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After eight weeks as an embryo, the baby is now called a fetus. Fingers and toes have soft nails. Mouth has 20 buds that will become baby teeth. Lungs acquire shape; vocal cords appear. You can hear your baby's heartbeat for the first time (10 to 12 weeks) using a special instrument called a Doppler transducer. For the rest of pregnancy, the kidney functions to secrete urine; all body organs will mature and the fetus will gain weight. By the end of this month, internal and external sex organs are recognizable and the fetus is four inches long, weighing a little over one ounce.

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The head is still large in proportion to the trunk. The face looks human. The fetus moves, kicks, swallows, and can hear your voice. The skin is pink and transparent. The umbilical cord continues to grow and thicken to carry enough nourishment from the mother to the baby – but it also can pass along hazards like tobacco, alcohol and other drugs. The placenta is now fully formed. By the end of the fourth month, the fetus is six to seven inches long and weighs about five ounces.

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The fetus becomes more active, turning from side to side and sometimes head over heels. Movements are strong enough for the mother to feel. The fingernails have grown to tips of fingers. The fetus sleeps and wakes at regular intervals. This is a month of active growth for the baby. By the end of the fifth month, the fetus is eight to twelve inches long and weighs between a half pound and one pound.

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The baby's skin is red and wrinkled and covered with fine, soft hair. At this stage the baby usually is too small and its lungs not ready for life outside its mother. If born now, the baby might survive with intensive care. The eyelids begin to part and the eyes open. The baby can hear. The finger and toe prints can be seen. By the end of the sixth month, the fetus is 11 to 14 inches long and weighs one to one and a half pounds.

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The baby can now open and close its eyes, suck its thumb and cry. He/she exercises by kicking and stretching. The baby responds to light and sound. If born now, he/she has a good chance for survival. By the end of the seventh month, fetus is about 15 inches long and weighs about three pounds.

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The baby is too big to move much but can kick strongly and roll around. The mother may notice the shape of an elbow or heel through her abdomen. Bones of the head are soft and flexible to make it easier for the baby to fit through the birth canal. Lungs may still be immature. If born before 37 weeks, the baby is premature but has an excellent chance for survival. By the end of the eighth month, the fetus is about 18 inches long and weighs about five pounds.

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At 37 to 42 weeks, the baby is considered full term. The baby's lungs are mature and ready to function on their own. During this month, the baby gains about a half pound per week. The baby usually drops into a head-down position and rests lower in the mother's abdomen. By the end of the ninth month, the baby weighs six to nine pounds and is 19 to 21 inches long.

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