Fertilization, when the egg and sperm come together to form a single cell, is the first event at the beginning of pregnancy. Fertilization occurs in the fallopian tubes. Over the next few days, this single cell divides into a multicellular cluster and the cluster of dividing cells travels through the fallopian tube into the uterus. It implants in the uterus (implantation) and begins to grow. From implantation until the 8th week of pregnancy, it is called an embryo. From the 9th week until birth, it is called the fetus.
What is the placenta?
The placenta is made up of some of these rapidly dividing cells. It is the life support unit for the fetus during pregnancy. Through the placenta, oxygen, nutrients and hormones pass from mother to baby. Residual products that are metabolized in the baby are also passed from the baby to the mother through the placenta, including destruction.
How does the uterus change during pregnancy?
During pregnancy, the lining of the uterus thickens and the uterine vessels dilate to nourish the fetus. As the pregnancy progresses, the uterus enlarges to give the fetus enough space. Just before birth, the uterus is several times the size it should be.
How does pregnancy end?
A normal pregnancy is about 40 weeks from the date of the last menstrual period. Pregnancy actually starts 2 weeks after the last menstrual period (date of fertilization). With these extra 2 weeks, the normal gestation period is 40 weeks.
How is the duration of pregnancy measured?
The gestation period is usually expressed in weeks. 36h+3d pregnancy means a pregnancy 3 days past 36 weeks. The 40-week gestation period is grouped into 3 trimesters. Each trimester lasts 12-13 weeks (about 3 months)
First trimester From the beginning of pregnancy to 13 weeks + 6 days
Second trimester From 14 weeks +0 days to 27 weeks + 6 days
Third trimester It covers the period from 28 weeks +0 days until delivery.
What is the expected date of birth?
The expected date of delivery is calculated from the first day of the last menstrual period. The expected date of delivery is the end of the 40th week after the last menstrual period. However, about one in 20 pregnant women give birth on this date. If the date of the last menstrual period is unknown, the expected date of birth can be calculated by measuring the CRL (head and buttock distance) during the first trimester ultrasound examination. If conception is by in vitro fertilization, the expected date of birth can be calculated according to the day of embryo transfer.