Progesterone is secreted in nonpregnant women during the latter half of the menstrual cycle by the corpus luteum and in large amounts by the placenta during pregnancy. It also is secreted in minute amounts by the adrenal cortex in both men and women. Progesterone prepares the endometrium for implantation of the fertilized ovum, decreases myometrial excitability, stimulates proliferation of the vaginal epithelium, and stimulates growth of the breasts during pregnancy. Although progesterone may promote sodium and water retention, its effect is weaker than that of aldosterone, which it directly antagonizes. The net effect is loss of sodium and water from the body.

• In menstruating women, progesterone levels vary in relation to the menstrual cycle.
• Therapy with estrogen, progesterone, or adrenocorticosteroids may produce elevated levels.

• Infertility of unknown etiology with failure to ovulate, indicated by low levels throughout the menstrual cycle
• Evaluation of response to therapy for infertility
• Support for diagnosing disorders associated with elevated progesterone levels (e.g., precocious puberty, ovarian tumors or cysts, and adrenocortical hyperplasia and tumors)
• High-risk pregnancy with suspicion of placental dysfunction, fetal abnormality, impending fetal jeopardy, threatened abortion, or toxemia of pregnancy, as indicated by lower than expected levels for the stage of pregnancy
• Support for diagnosing disorders associated with decreased progesterone levels (e.g., panhypopituitarism, Turner's syndrome, adrenogenital syndrome, and Stein-Leventhal syndrome)

Nursing Care Before the Procedure

Client preparation is the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).

• It is recommended that any drugs that may alter progesterone levels be withheld for 12 to 24 hours before the test, although this practice should be confirmed with the person ordering the study.
• In menstruating women, the phase of the menstrual cycle should be ascertained, if possible. If the test is being performed to detect ovulation, the client should be informed that it may be necessary to obtain a series of samples over a period of several days to detect the normal variation in progesterone levels.

A venipuncture is performed and the sample collected in a green-topped tube. The sample should be handled gently to avoid hemolysis and transported promptly to the laboratory.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample.

• Resume any medications withheld before the test.
• Complications and precautions: Assess increased or decreased levels in relation to age, menstrual or pregnancy status, and 24-hour urinary pregnanediol level.