Pregnancy is an intricate development of cells which multiply and eventually form a baby. Hormones play a complex role in this metamorphosis and assist physicians in determining the healthy progression of a pregnancy or potential problems. Understanding what these key hormones do and the information they provide may help in understanding the process.
Functions of hCG
Human Chorionic Gonadotropin, or hCG, is a hormone only present during pregnancy 1. It is produced by the cells that make up the placenta and provides nourishment for the egg once it is fertilized and attaches to the uterus. Levels of hCG are present throughout pregnancy, however they increase dramatically during the first trimester and then begin to level off and eventually decline.
Functions of Progesterone
Progesterone is the hormone that helps maintain a pregnancy for the entire gestation. Prior to conception progesterone is released by the corpus luteum to help build up the uterine lining in preparation for implantation. Once fertilization occurs, the corpus luteum will continue to release progesterone until week 10 of the pregnancy, at which time the placenta has developed enough to take over. Progesterone also limits the immune response, prevents early contractions and decreases prostaglandins.
Levels of hCG
During pregnancy, the levels of hCG will vary from one woman to another. When analyzing hCG levels, the most important factor is that the numbers are doubling, at least, every 48 to 72 hours. To achieve a positive pregnancy test, the hCG level must be at 25 mIU/ml or higher. During a normal pregnancy, hCG levels will start around 5 mIU/ml -- milli-International Units per Milliliter -- and may eventually rise to around 300,000 mIU/ml by the end of the first trimester. At that point ultrasounds are the best indicator of a healthy pregnancy rather than hCG levels.
Levels of Progesterone
Progesterone levels vary considerably from one woman to another during pregnancy and also rise as the pregnancy progresses. A normal gestation will see an increase in progesterone of 1 to 3 ng/ml, or nanograms per milliliter, about every two days. A guide for progesterone levels is 9 to 46 ng/ml in the first trimester, increasing to about 17 to 146 ng/ml in the second trimester with a culmination in the third trimester of 49 to 300 ng/ml. It is important to remember the increase in progesterone is often more important than the actual number.
In cases where a pregnancy is not progressing normally, a woman’s hormone levels may indicate a problem. If there is a threatened miscarriage both hCG and progesterone will be low and not increasing as expected. When a miscarriage does occur, both hormone levels will drop significantly. In the case of an ectopic pregnancy, hCG levels may increase normally for a while but progesterone will stay low and not progress. It is important to refer to your doctor if you suspect a problem. HCG and progesterone levels vary so dramatically from one woman to another that one woman’s hormone levels indicating miscarriage could be the same levels for another woman’s successful pregnancy.
In the case of an ectopic pregnancy, hCG levels may increase normally for a while but progesterone will stay low and not progress. Once fertilization occurs, the corpus luteum will continue to release progesterone until week 10 of the pregnancy, at which time the placenta has developed enough to take over. At that point ultrasounds are the best indicator of a healthy pregnancy rather than hCG levels.
- pregnant woman image by Valentin Mosichev from Fotolia.com