No matter what your feelings are about this pregnancy, you have probably experienced some sort of fear also.  A baby is a big change, and may hold lots of unknowns.  However, we would like to solve some of those unknowns by helping you to understand some of the basic things the next nine months will hold for you should you choose to carry to term. First of all, your baby’s gestational age is measured from the first day of your last period (even though the little one wasn’t actually conceived until about two weeks after that).

Conception: The egg and sperm unite to form a single cell called a zygote.  The zygote contains 46 chromosomes (23 chromosomes from each parent).  This tiny new call, smaller than a grain of salt, contains all the genetic information for every detail of this new life – hair and eye color, fingerprints, physical appearance, gender, etc.  This new life is now called an embryo.
Week 3: The embryo continues to grow as the cells divide and it travels to the uterus and begins to implant.  Once the embryo is implanted the mother’s body begins to produce hormones to sustain the pregnancy.
Week 4: By now the embryo is completely implanted and the mother’s body is producing enough hormones in her blood to allow a pregnancy test to read positive.
Week 5: The child’s heart has begun to beat and can be detected on an ultrasound.  The first sign of brain development are evident and organ and muscle systems are beginning to develop.
Week 6: The origin of the entire central nervous system (brain and spinal cord) is laid down.  The eyes, jaws and limb buds are now visible.
Week 7: The upper limbs are paddle shaped and the lower limbs are flipper like.  The embryo is making its own blood in it’s liver, bone marrow and spleen.
Week 8: The elbows and fingers are now visible.  The back and neck can bend and at times the embryo has spontaneous movement.  The embryo is now about ½ inch long.
Week 9: The intestines begin to develop as well as the embryo’s limbs and fingers develop bony tissues which will calcify and harden.
Week 10: The arms and legs purposefully move for the first time in the child’s life.  There are also now 20 tiny tooth buds present in the gums and the eyelids are developing.
Week 11: Because the developing baby has all the major organ systems and is distinctly human, it is no longer called and embryo but a fetus.  The baby can now yawn and suck, and it’s body will begin to grow rapidly.
Week 14: The fetus is now 3 inches long and able to urinate and swallow.  The beginnings of fingernails and toenails are present and the baby is coordinated enough to find it’s thumb and suck on it.
Week 16: you can not most likely see the gender of the baby on the ultrasound.
Week 18: The baby’s skeleton is hardening and you can see the external ear on the baby’s head.
Week 20: The baby’s movement can now be felt by the mother.  If the baby is female her ovaries have formed and they now contain eggs.
Week 22: The pregnancy is now close to half over, and the mother is most likely beginning to “show.” The baby’s eyelids remain closed and hair is visible on its head and body.  The baby can not feel pain.
Week 24: The baby now weighs approximately one pound and a baby born now has a chance of survival (although the fight would be great).  The baby can hear it’s mothers voice and heartbeat. 
Week 28: The fetal skin becomes more smooth as the baby builds up fat.  The eyelashes can be seen and the tongue is now fully functioning with taste buds.
Week 34: The baby is now approximately 19 inches long and 5 pounds in weight.  The child also now has active wake and sleep cycles.
Week 40: The child is now typically head down in the mothers pelvis and waiting for birth.  It has a more plump body and its hands can form a firm grasp.