How does pregnancy begin?
Fertilization, the union of an egg and a sperm into a single cell, is the first step in a complex series of events that leads to pregnancy. Fertilization takes place in the fallopian tube. Over the next few days, the single cell divides into multiple cells. At the same time, the small cluster of dividing cells moves through the fallopian tube to the lining of the uterus. There it implants and starts to grow. From implantation until the end of the eighth week of pregnancy, the baby is called an embryo. From the ninth week of pregnancy until birth, it is called a fetus.
What is the placenta?
The placenta is formed from some of these rapidly dividing cells. The placenta functions as a life-support system during pregnancy. Oxygen, nutrients, and hormones from the mother are transferred across the placenta to reach the baby, and waste products from the baby are transferred to the mother for removal.
How will my uterus change during pregnancy?
During pregnancy, the lining of your uterus thickens and its blood vessels enlarge to provide nourishment to the fetus. As pregnancy progresses, your uterus expands to make room for the growing baby. By the time your baby is born, your uterus will have expanded to many times its normal size.
How long does pregnancy last?
A normal pregnancy lasts about 40 weeks from the first day of your last menstrual period (LMP). Pregnancy is assumed to start 2 weeks after the first day of the LMP. Therefore, an extra 2 weeks is counted at the beginning of your pregnancy when you are not actually pregnant. Pregnancy “officially” lasts 10 months (40 weeks)—not 9 months—because of these extra weeks.
Click on the FAQs below to expand
How is the length of my pregnancy measured?
Pregnancy can be divided into weeks and sometimes days. A pregnancy that is “36 and 3/7 weeks” means “36 weeks and 3 days of pregnancy.” The 40 weeks of pregnancy often are grouped into three trimesters. Each trimester lasts about 12–13 weeks (or about 3 months):
What is the estimated due date (EDD)?
The day your baby is due is called the estimated due date (EDD). Only about 1 in 20 women give birth on their exact due dates. Still, the EDD is useful for a number of reasons. It determines your baby’s gestational age throughout pregnancy so that the baby’s growth can be tracked. It also provides a timeline for certain tests that you will have throughout your pregnancy.
How is my EDD calculated?
Your EDD is calculated from the first day of your LMP. But when the date of the LMP is uncertain, an ultrasound exam may be done during the first trimester to estimate the due date. If you have had in vitro fertilization, the EDD is set by the age of the embryo and the date that the embryo is transferred to the uterus.
What happens during weeks 1–4 of pregnancy?
What happens during weeks 5–8 of pregnancy?
What happens during weeks 9–12 of pregnancy?
What happens during weeks 13–16 of pregnancy?
What happens during weeks 17–20 of pregnancy?
What happens during weeks 21–24 of pregnancy?
What happens during weeks 25–28 of pregnancy?
What happens during weeks 29–32 of pregnancy?
What happens during weeks 33–36 of pregnancy?
What happens during weeks 37–40 of pregnancy?
Cell: The smallest unit of a structure in the body; the building blocks for all parts of the body.
Egg: The female reproductive cell produced in and released from the ovaries; also called the ovum.
Embryo: The developing organism from the time it implants in the uterus up to 8 completed weeks of pregnancy.
Fallopian Tube: One of a pair of tubes through which an egg travels from the ovary to the uterus.
Fertilization: Joining of the egg and sperm.
Fetus: The developing organism in the uterus from the ninth week of pregnancy until the end of pregnancy.
Gestational Age: The age of a pregnancy calculated from the number of weeks that have elapsed from the first day of the last normal menstrual period.
Hormones: Substances made in the body by cells or organs that control the function of cells or organs. An example is estrogen, which controls the function of female reproductive organs.
In Vitro Fertilization: A procedure in which an egg is removed from a woman’s ovary, fertilized in a laboratory with the man’s sperm, and then transferred to the woman’s uterus to achieve a pregnancy.
Oxygen: A gas that is necessary to sustain life.
Placenta: Tissue that provides nourishment to and takes away waste from the fetus.
Sperm: A cell produced in the male testes that can fertilize a female egg.
Surfactant: A substance produced by cells in the respiratory system that contributes to the elasticity of the lungs and keeps them from collapsing.
Trimesters: The three 3-month periods into which pregnancy is divided.
Ultrasound Exam: A test in which sound waves are used to examine internal structures. During pregnancy, it can be used to examine the fetus.
Uterus: A muscular organ located in the female pelvis that contains and nourishes the developing fetus during pregnancy.