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You’ve waited three minutes and now stare at a line on the pregnancy test that confirms your suspicion—you’re going to be a mommy!

Pregnancy, or gestation, is measured in weeks and lasts approximately 40. The time is divided into thirds called trimesters. The first trimester is considered among medical experts to be the most critical in the baby’s development. During this 14-week period the baby grows from an embryo to a fetus and most organ systems develop. It is also a time that can be an adjustment to the mother-to-be. Her body undergoes tremendous changes as the baby develops.

The first two weeks of pregnancy involve no embryo at all. This is the time when the uterus is preparing for the implantation of the egg if conception occurs. During this time experts recommend that if you are trying to get pregnant eat healthy and quit smoking and drinking alcohol.
Week three is when fertilization of the egg typically occurs. You will probably not even notice that great changes are to come. Week four is when the growing embryo plants itself into the uterus. This triggers the production of HCG hormone that will cease ovulation and begin the ball rolling for other changes needed to make a baby. By this time some early symptoms may appear such as breast tenderness and tiredness. By week five you’ve missed your period and the pregnancy can be confirmed with an at-home test. The baby’s placenta and umbilical cord have developed and the embryo is about a quarter-inch long. During this week the baby’s heart begins to beat. You may also notice that your breasts have enlarged to prepare to produce milk.
During week six, the baby’s brain, spinal cord, kidneys and other major organs begin to form. The baby’s head has eyespots and the body develops buds where its arms and legs will be. By this time you could be feeling what is called morning sickness, due to the hormone changes.
At week eight the embryo is about an inch long and the uterus is about the size of an orange. The baby has toes, fingers, eyelids and hair. You may have bloating, and food is passed through your system more slowly.
During week nine, the heartbeat is detectable using instruments that are placed on the abdomen. All of its organs have formed and it crosses the threshold from being an embryo to being a fetus.
During week twelve your uterus rises up in you abdomen. The fetus is about two inches long and its bones are developing. The final week of the first trimester, week 14, is a milestone. Chances of miscarriage drop to about five percent. Now all that is needed is time for the baby to grow.