Life Stages

All women go through puberty and enter their “reproductive years,” or the time when they are typically able to become pregnant. Many women do conceive at some point during this time. Later in life, women experience another natural transition called menopause, which marks the end of the reproductive years. Read more about these life stages and the hormonal changes each one entails.


Girls typically begin puberty at age 9 - 14. It is initiated by the pituitary gland, which is part of the hormonal system. The ovaries become larger and produce hormones like estrogen, which drive the physical changes during this transition. Breasts begin to develop, height increases, pubic hair appears, and sweat glands become more active. Many young women experience symptoms like acne, body odor, and mood swings as a side effect of the hormonal changes happening.

Typically, a girl experiences these changes before getting her menarche, or first period. The menarche marks the completion of puberty, and a young woman is now able to become pregnant. It's normal for a woman to have somewhat irregular periods in the first year or two after her menarche until her body settles into a more regular cycle.

The Reproductive Years

From the completion of puberty until a year after her last menstrual cycle, a woman is considered to be in her reproductive years, lasting from approximately ages 13 - 45. During this time, hormone levels are relatively stable, though estrogen and progesterone levels do fluctuate naturally over the course of the menstrual cycle to direct the various parts of it. As a result of these fluctuations, a woman may experience premenstrual syndrome (PMS), which consists of symptoms like breast pain, acne, mood swings, cramps, and headaches in the days before and during her period. The symptoms may even appear up to two weeks before bleeding begins.

Some women are more susceptible to PMS than others, and while the exact reason for this is unknown, it may be related to sensitivity to hormonal changes, outside stress, and poor nutrition. It is estimated that up to 85% have at least one symptom of PMS during their cycle. Particularly severe PMS - referred to as premenstrual dysphoric disorder - is thought to affect about 3 - 8% of women.


Many women become pregnant at some point during their reproductive years. To sustain the pregnancy, levels of progesterone and other hormones increase exponentially. These hormonal changes affect not just the reproductive system, but nearly every organ in the body. As the fetus grows throughout pregnancy, body aches are common, but other symptoms are unique to certain stages of pregnancy.

The nine-month pregnancy is divided into three trimesters. During the first trimester - weeks 1 - 12 - a woman may experience symptoms like mood swings, headaches, cravings, tender breasts, fatigue, and constipation. During the second trimester, these symptoms typically fade, but swelling, itching, and dark patches on the skin may appear. During the last trimester, common symptoms include heartburn, trouble sleeping, swelling, and breast tenderness. While some of the symptoms during pregnancy are simply caused by the growing baby and the shifting of the organs, hormonal changes also play a large role.


Postpartum - also referred to as the lactation or breastfeeding period - is right after a woman gives birth. Within 48 hours after delivery, estrogen and progesterone levels that were especially high throughout pregnancy sharply decrease. The most well-known and concerning symptom of this stage is postpartum depression, which is thought to affect 10 - 15% of women at this time. Estrogen and progesterone also influence the regulation of neurotransmitters, so the sudden drop in these hormones after a woman gives birth can result in mood problems. Stress and fatigue from caring for a new baby and also add to depression and other symptoms of this stage.

The Menopause Transition

For most women, after about 30 years of menstruation, the menstrual cycle gradually winds down in what is known as the menopause transition. Menopause occurs on the day when a woman has not had a period for 12 consecutive months; after that, she is considered postmenopausal.

The average age of menopause in the U.S. is 51, but in the 2 - 10 years prior, hormone levels fluctuate - often significantly - as the body prepares to end menstruation for good. These fluctuations can cause many symptoms, the most well-known being hot flashes, night sweats, mood swings, irregular periods, and low libido. However, there are many more lesser-known symptoms of menopause, such as memory lapses, itchy skin, headaches, bloating, and dizziness, among others.

Once a woman is postmenopausal, sex hormones remain at a consistently low level. While the symptoms caused by constant fluctuations typically disappear, these low levels mean that a woman is at greater risk for certain conditions, such as osteoporosis.

Each stage of a woman's reproductive life is shaped by hormonal changes. While each stage is a natural part of being a woman, the hormonal fluctuations may have uncomfortable side effects. Fortunately, by balancing hormone levels, these symptoms are largely manageable, leading to greater wellness throughout all stages of life.