| Progesterone is a female hormone that is essential for successful conception and a healthy pregnancy. In fact, the word progesterone is etymologically related to the Latin root gestare - meaning to bear or carry. During a woman's cycle, progesterone levels rise rapidly to provide a fertile environment for the fertilized egg. This rise is accompanied by an increase in body temperature at ovulation that lasts through most of the luteal phase (the second half of the menstrual cycle after ovulation). If fertilization does not occur, progesterone levels fall dramatically triggering the menses where the secretory endometrium is shed. Progesterone and Pregnancy Progesterone encourages pregnancy by preparing the endometrium for implantation of the fertilized egg. Following implantation, progesterone is produced by the placenta to prevent rejection of the developing embryo or fetus. During the pregnancy, progesterone: - Strengthens and maintains the secretory endometrium, which sustains the embryo throughout pregnancy.
- Creates a nutrient rich environment for the baby by increasing gylcogen and arterial blood to the lining of the uterus.
- Maintains the functions of the placenta and fights off unwanted cells near the womb that could cause damage to the placenta or fetus.
- Keeps the uterus from contracting.
- Causes the cervix to thicken and create a mucous plug, which prevents bacteria from entering the uterus.
- Strengthens the pelvic walls in preparation for labor.
- Stimulates the growth of breast tissue.
- Prevents lactation until after the birth (with estrogen).
The placenta produces both progesterone and estrogen for the duration of the pregnancy and the levels get higher and higher right up to just before the birth. At the end of the pregnancy, a decrease in the level of progesterone secreted by the placents stimulates the beginning of contractions that lead to birth. Fertility and Miscarriage Because of the important role of progesterone in pregnancy, it is associated with both fertility and miscarriage. Supplements of natural progesterone are sometimes prescribed as a fertility treatment. These are generally prescribed in the form of a cream that is rubbed into the abdomen and thighs or as a vaginal suppository or injection. The chief cause of early loss of pregnancy is now thought to be luteal phase failure, where ovarian production of progesterone fails to increase sufficiently during the first several weeks after fertilization. When a woman has experienced several early miscarriages and luteal phase failure is suspected, natural progesterone supplementation may be prescribed. A health care provider can easily monitor a woman's progesterone levels with saliva hormone assays. Your Health Care Professional and Women's Health America can work together to determine if progesterone therapy is appropriate for you. We offer saliva testing for assessment of hormone levels with interpretation and recommendations for replacement therapy through our Restore® Program. For additional general information about pregnancy, visit www.pregnancy.org . | 
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