As soon as sperm meets egg, hormonal changes begin. Before you know you have conceived, your progesterone and estrogen hormones have begun an intricate and complex process that lays the foundation for a healthy pregnancy and birth. Your health care provider may begin testing your blood hormone levels early in your pregnancy.
Both hormones, estrogen and progesterone, are essential to the process of healthy implantation of the fertilized egg in your uterus and gestation, or growth, of the fetus. The levels of these important hormones will vary based on the gestational age of the fetus. Estrogen and progesterone are produced and secreted by your ovaries. The presence of these two hormones in your blood signals the lining of your uterus to grow. Increasing the amount of nutrients available in the uterine lining is important, because it supports implantation of the fertilized egg.
The follicle on your ovary that releases the egg is called the corpus luteum. It releases progesterone, which helps prepare the lining of your uterus for the possible implantation of a fertilized egg. Once an egg is implanted, your blood levels of estrogen and progesterone rise sharply to prevent release of another egg from your ovaries. The fertilized egg that is successfully implanted in the lining of your uterus begins rapid cell division and growth. In early pregnancy, the growing egg releases another hormone, called human chorionic gonadotropin, or hCG. The purpose of this hormone in the early stages of pregnancy is further stimulation of your ovaries to produce more estrogen and progesterone to support your pregnancy.
In early pregnancy, progesterone levels increase with the gestational growth and age of your fetus. Progesterone levels vary during your menstrual cycle. Your progesterone level most likely will be between 1 to 28 ng/ml during the mid-luteal phase, or once the corpus luteum has released an egg. Some women take fertility medications to support their hormone levels. If you do, your levels might be different during this time. The average progesterone level, if you are not taking medication, is over 10 ng/dl during this phase. If you are taking fertility medication, the average progesterone level is over 15 ng/dl. Blood progesterone levels increase during pregnancy. The average levels during the three trimesters are 9 to 47 ng/ml for the first trimester, 17 to 146 ng/ml for the second trimester and 49 to 300 ng/ml for the third trimester.
According to the American Congress of Obstetricians and Gynecologists, once your fertilized egg, called a blastocyst, has implanted itself in your uterine lining, a section begins to develop into what will become your placenta. hCG is secreted to increase ovarian production of estrogen and progesterone and to stop your menstrual periods. Once you reach weeks nine to 10 of your pregnancy, your placenta will begin producing much of the estrogen and progesterone required to support your pregnancy.
Hormone levels differ in each pregnancy. What is normal for your sister or friend may not be normal for you. It is best to work closely with your health care provider, because suggested normal hormone levels are just that - suggestions. Your doctor or midwife will know what is best for you.
During the early stages of pregnancy, your hormone levels grow rapidly. Your high levels of estrogen and hCG may also cause morning sickness. If the nausea and vomiting is severe and you begin to become dehydrated or lose weight, you may be suffering from a condition called hyperemesis gravidarum. It is important to speak with your health care provider, because she can treat this serious problem with medication to relieve vomiting, and IV fluids to combat dehydration.