This paragraph will be on your test!

The fertilized egg attaches itself to the walls of the unterus and begins to grow. The endometrium, or lining, begins to build up layers of nutrient-ricj blood. The connecting tissue between the womb and the baby is called the placenta. Nourishment and oxygen are carried from the mother's bloodstream to the developing baby through the umbilical cord. The male cell is known as the sperm, while the female cell is known as the egg. Once they have joined, the new cell is called a zygote. In the first trimester, the baby'a major organs begin to develop. The chance of a miscarriage or birth defect occuring now is the highest, sometimes without the mother even realizing she was pregnant. The doctoe may perform a (an amniocentesis (withdrawing some of the amniotic fluid) to look for possible birth defects. An ultrasound may be performed later in the pregnancy for two reasons, age of the fetus and the sex of the child. This procedure is harmless to the baby, and uses sound waves to look at the fetus. A baby who is born premature, or under 5 pounds, may have special helath problems. If the mother carries the baby full term, the baby will weigh around 6-7 pounds, on average. She will know she is going into labour because her water may break and contractions will occur. The cramps caused by the tightening of abdominal muscles during labour are called contraction. Usually, a nurse or midwife is present, along with an obstetrician for the delivery. The latter is extremely helpful if there are complications during the delivery.