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Conception
A woman's due date is calculated from the first day of her last menstrual period. Conception occurs two weeks from that day -- that's when you're truly considered to be pregnant! Millions of sperm swim upstream on the quest to fertilize an egg. Only one successfully penetrates the egg, forming the genetic makeup that will determine the sex, physical appearance, intelligence, and personality of the baby. -
Embryo forms
By the 4th week of your pregnancy, the ball of cells that is developing into your baby is the size of a poppy seed. By the 5th week, the ball of cells resembles a tadpole and is the size of a peppercorn; the development of the brain, spinal cord, and heart are under way, and facial features begin to form. An umbilical cord connects the baby to your body. -
Embryo to Fetus
At week 9, your baby has graduated from embryo to fetus. It is still too early to determine whether the baby is a boy or girl, but you'll soon feel the jerks felt from baby's hiccups -- one of the earliest moves a fetus makes. Facial features continue to develop and by the end of 10 weeks, Baby has developed 90 percent of the anatomical structure adults have. -
Second Trimester
You are now entering your second trimester. All of your baby's internal organs have formed and will continue to mature through the second and third trimesters. Though his eyes remain closed, your baby can now begin to hear. Talk and read to him so he can get to know the sound of your voice. -
Feeling the baby move
You'll start to feel your baby's fluttering movements (called quickening) between now and 22 weeks. Get ready, mama: Feeling the baby kick is one of the most magical parts of being pregnant. By the 22nd week, your baby is as big as a coconut. During this period, you can also find out whether you're having a boy or a girl -
The gender is determined
Women have two X chromosomes, and men have an X and Y chromosome; each sperm carries one of the two, leading the male's sperm to determine the baby's sex. Humans have about 25,000 genes, but only one gene located on the Y chromosome is required for male development. -
Developing Senses
Your baby now weighs a full pound and her ability to see, hear, smell, taste, and feel is getting stronger each day. Vocal cords have developed and she's beginning to recognize your voice and listen to the sounds of the things going on in your body. -
Growing Big
Your baby now weighs about three pounds, roughly the size of a melon. She'll continue to gain about a pound and a half per week until she's born. Your body is sending her antibodies that will protect her from infection. -
Birth
In preparation for birth, your baby is now upside down in your uterus. If he's not, your doctor may be able to perform some techniques to prepare him for delivery. Once your baby's in the upside down position, his head will rest against your cervix, which is opening or dilating so he can pass through the birth canal.