Most pregnancy tests look for human chorionic gonadotropin (hCG). The hormone hCG is secreted by the outer layer of the blastocyst, called the synctiotrophoblast, and later the placenta.

The menstrual cycle is the process of preparing the human female body for potential pregnancy. The cycle can be divided into two stages—the ovarian cycle and the uterine cycle. The uterine cycle has three phases that are called menstruation, the proliferative phase, and the secretory phase.

Premenstrual syndrome (PMS) is a set of physical and emotional symptoms that occur 1 to 2 weeks before menstruation. The exact cause of PMS is not known but most likely involves hormonal changes, with the severity of PMS being influenced by environmental factors. Common symptoms include acne, bloating, and mood changes.

Menstruation is the part of the female reproductive cycle in which the uterine lining is expelled through the vagina when the released oocyte is not fertilized. The onset of menstrual periods is called menarche and the cessation is called menopause. Menstruation occurs due to a decrease in progesterone levels and is often accompanied by cramping.

During the proliferative phase of the menstrual cycle, the high levels of estrogen cause the development of the uterine lining and fertile cervical mucus. This fertile cervical mucus is alkaline and thin to allow for sperm penetration.

Progesterone birth control pills function to increase progesterone levels in the individual. This inhibits the secretion of gonadotropin-releasing hormone (GnRH), which, in turn, inhibits luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion. The drops in LH and FSH levels halt follicle development, thereby preventing ovulation.

Combination birth control pills contain estrogen and progesterone. Supplementing progesterone levels inhibit luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion, follicle development, and ovulation. Estrogen supplementation decreases FSH, thereby inhibiting follicle development and ovulation. The combination pill decreases breakthrough bleeding but has more withdrawal symptoms.

Common methods of fertility testing include: calendar tracking, ovulation predictor kits, and monitory physical symptoms. Calendar tracking determines fertility by cycle length. Ovulation predictor kits measure luteinizing hormone (LH) levels in an individual’s urine. Monitoring physical symptoms such as cervical mucus and basal body temperature are also a good method of tracking fertility.

During the menstrual cycle, the time when fertility peaks is at ovulation and a few days preceding it. At this point, sperm can survive in the female reproductive tract until oocyte release.

Amenorrhea is a condition where menstrual cycles are irregular and rare, occurring every 3 to 6 months.