Pregnancy Vocabulary : A—Amenorrhea

We're at the beginning of the alphabet, so let's start with the beginning of pregnancy! Amenorrhea is the absence of a menstrual period and often is the first sign that a baby is in the making. By the time your period is late, you're already two weeks past conception—and considered 4 weeks pregnant. Confusing? Obstetricians and midwives begin counting your weeks from your last actual menstrual period. Just think of it as getting two free weeks of pregnancy behind you.

Physiological states of amenorrhea are seen during pregnancy and lactation (breastfeeding), the latter also forming the basis of a form of contraception known as the lactational amenorrhoea method. Outside of the reproductive years there is absence of menses during childhood and after menopause.

Amenorrhoea is a symptom with potential causes. Primary amenorrhoea (menstruation cycles never starting) may be caused by developmental problems such as the congenital absence of the uterus, or failure of the ovary to receive or maintain egg cells. Also, delay in pubertal development will lead to primary amenorrhoea. It is defined as an absence of secondary sexual characteristics by age 14 with no menarche or normal secondary sexual characteristics but no menarche by 16 years of age. Secondary amenorrhoea (menstruation cycles ceasing) is often caused by hormonal disturbances from the hypothalamus and the pituitary gland, from premature menopause or intrauterine scar formation. It is defined as the absence of menses for three months in a woman with previously normal menstruation or nine months for women with a history of oligomenorrhoea.

Amenorrhea is the absence of menstrual bleeding and may be primary or secondary.

Primary amenorrhea is the absence of menstrual bleeding and secondary sexual characteristics (for example, breast development and pubic hair) in a girl by age 14 years or the absence of menstrual bleeding with normal development of secondary sexual characteristics in a girl by age 16 years.

Secondary amenorrhea is the absence of menstrual bleeding in a woman who had been menstruating but later stops menstruating for 3 or more months in the absence of pregnancy, lactation (the ability to breastfeed), cycle suppression with systemic hormonal contraceptive (birth control) pills, or menopause.

For a woman to have regular menstrual cycles, her hypothalamus, pituitary gland (see Anatomy of the Endocrine System), ovaries, and uterus should all be functioning normally. The hypothalamus stimulates the pituitary gland to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FSH and LH cause the ovaries to produce the hormones estrogen and progesterone. Estrogen and progesterone are responsible for the cyclical changes in the endometrium (uterine lining), including menstruation. In addition, a woman’s genital tract should be free of any abnormalities to allow the passage of menstrual blood.