HCG, which is short for human chorionic gonadotropin, and progesterone are two of the crucial pregnancy hormones that help a woman's body maintain a pregnancy. Because these hormones are so closely linked to pregnancy, physicians sometimes use them to check for, and monitor the progress and health of, a pregnancy.
Female Reproductive Function
HCG isn't a part of the hormonal makeup of non-pregnant women, but progesterone is. During your reproductive cycle each month, after you ovulate, specialized tissue in your ovary secretes estrogen and progesterone. This tissue, called the corpus luteum, helps to prepare your uterus for implantation of a fertilized egg, should fertilization occur. The rising progesterone levels cause the uterine lining to develop. If no egg implants within about two weeks, the corpus luteum dies, and you stop producing as much progesterone. This causes menstruation.
Fertilization
If conception occurs, it's the job of the fertilized egg to send a signal to your body indicating that the uterine lining is needed, and shouldn't be sloughed off. The egg does this by secreting the hormone hCG, which comes from the chorionic tissue of the egg. This tissue goes on to form the placenta and sacs around a developing baby. HCG helps keep the corpus luteum alive, explains Dr. Lauralee Sherwood in her book "Human Physiology."
Time Frame
Since the fertilized egg begins producing and secreting hCG soon after conception, and because your body doesn't produce hCG at any other time, you can test for hCG in your blood or urine to test for pregnancy. Physician's offices sometimes use blood hCG tests, but they can also use urine tests. Home pregnancy tests also rely upon urine hCG levels, explain Heidi Murkoff and Sharon Mazel in their book "What To Expect When You're Expecting."
Hormone Levels
Under normal circumstances, progesterone levels rise quite high in early pregnancy. HCG levels, too, reach high levels. Physicians will sometimes test hCG and progesterone levels to provide an indication of whether a pregnancy is progressing normally, according to the Advanced Fertility Center of Chicago. In normal pregnancies, progesterone levels are above 15 ng/mL. Lower levels can indicate an ectopic pregnancy or likelihood of miscarriage. HCG levels should double every few days to indicate a normal pregnancy.
Effects
There are several effects of high levels of hCG and progesterone in early pregnancy, though most women become accustomed to high hormone levels by their second trimesters, and symptoms begin to dissipate. Murkoff and Mazel note that early pregnancy fatigue, nausea and headaches --- many of which are the earliest symptoms of pregnancy --- stem from high levels of hormones. In general, however, the higher the hormone levels, the healthier the pregnancy.
References
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
- "What to Expect When You're Expecting"; Heidi Murkoff and Sharon Mazel; 2008
- Advanced Fertility Center of Chicago: Hormone Levels
