Women and the Reproductive Lifecycle

Two of the most significant differences between puberty in girls and boys are the age which puberty begins and the major sex steroids involved. Girls attain reproductive maturity about 4 years after the first physical changes of puberty appear. In contrast, boys accelerate more slowly but continue to grow for about 6 years after the first visible pubertal changes.⁷ Any increase in height beyond the post-pubertal age is uncommon for both boys and girls.
 
In North America, the first sign of puberty for young girls—breasts budding—normally occurs between ages 8 and 13, with an average age of 10 years.⁸

•  The average duration of puberty is 4 years but can range from 1.5 to 8 years.⁸
• The first menstrual period for U.S. girls today occurs on average between ages 12 and 13, compared with age 14 for girls in 1900. Regular ovulation is established by about 20 menstrual cycles after the first period.⁸
• A normal menstrual cycle lasts about 28 days but can vary from 21 to 45 days in adolescents.⁸
• In developing countries, abnormal uterine bleeding appears to affect about 5–15% of women of reproductive age.⁹
• Abnormal uterine bleeding is a leading indication for hysterectomy, the most common non-obstetric operation in women in both the United States and the United Kingdom.⁹

Amenorrhea—lack of a menstrual period. This term is used to describe the absence of a period in:⁶

• Young women who haven’t started menstruating by age 15
• Women and girls who haven’t had a period for 90 days, even if they haven’t been menstruating for long
   

• Causes include:

          • Pregnancy

          • Breastfeeding

          • Extreme weight loss

          • Eating disorders

          • Stress

 
Dysmenorrhea—painful periods, including severe cramps. Menstrual cramps in teens are caused by too much of a chemical called prostaglandin.⁶

Both women and men can have problems that cause infertility. About one-third of infertility cases are caused by the male.¹²

Risk factors that may impact a woman’s ability to have a baby include:¹²

• Age
• Smoking
• Excessive alcohol use
• Stress
• Poor diet
• Athletic training
• Being overweight or underweight
• Sexually transmitted infections (STIs)
• Health problems that cause hormonal changes, such as polycystic ovarian syndrome and primary ovarian insufficiency

Most cases of infertility in women are caused by problems with ovulation. Signs that a woman is not ovulating normally include irregular or absent menstrual periods.¹²
 
Ovulation problems are often caused by polycystic ovarian syndrome (PCOS). PCOS is a hormone-imbalance problem that can interfere with normal ovulation. PCOS is the most common cause of female infertility.¹²
 
Primary ovarian insufficiency (POI) is another cause of ovulation problems. POI occurs when a woman’s ovaries stop working normally before she is 40 years of age. POI is not the same as menopause.¹²
 
Less-common causes of infertility in women include:¹²

• Blocked fallopian tubes due to pelvic inflammatory disease, endometriosis, or surgery for an ectopic pregnancy
• Physical problems with the uterus
• Uterine fibroids, which are noncancerous clumps of tissue and muscle on the walls of the uterus

The factors that place a pregnancy at risk can be divided into four categories:
 
Existing health conditions

• High blood pressure
• Polycystic ovary syndrome
• Diabetes
• Kidney disease
• Autoimmune disease
• Thyroid disease
• Infertility
• Obesity
• HIV/AIDS

 
Age

• Teen pregnancy
• First-time pregnancy after age 35

 
Lifestyle factors

• Alcohol use
• Cigarette smoking

 
Conditions of pregnancy

• Multiple gestation
• Gestational diabetes
• Preeclampsia and eclampsia

In addition to a missed period, the earliest signs and symptoms of pregnancy might include:

• Tender, swollen breasts
• Nausea, with or without vomiting
• Increased urination
• Fatigue
• Food aversions or cravings
• Slight vaginal bleeding
• Cramping
• Mood swings
• Dizziness
• Constipation

For both women and men, the changes in reproductive-hormone levels have an impact on health later in life. These changes, however, appear to have a greater impact on the health of women in comparison to their male counterparts.²⁰

Common menopausal symptoms include:²⁰

• Hot flashes
• Night sweats
• Difficulty sleeping
• Vaginal changes
• Changes in sex drive
• Mood changes
• Urinary changes/stress incontinence
• Skin changes

A major effect of menopause is a significant decrease in estrogen. It is unknown why some women pass through menopause with mild or no symptoms, while others struggle with more-bothersome symptoms.²⁰

• Approximately 55% of women going through menopause don’t do anything at all to treat symptoms.²⁰
• Approximately 75% of women experience hot flashes and night sweats at some point during perimenopause.²⁰
• About two-thirds of North American postmenopausal women experience hot flashes, and an estimated 10–20% of postmenopausal women have severe hot flashes. Most flashes last between 30 seconds and 5 minutes.²⁰
• Approximately 25% of women who experience hot flashes and night sweats have them for more than 5 years.²⁰

Osteoporosis
Women lose an average of 25% of their bone mass from the time of menopause to age 60, due in large part to the loss of estrogen.²⁰

• Estrogen loss can also increase the risk of certain diseases, such as osteoporosis, which leads to hip, wrist, and spine fractures.²⁰
• Approximately 50% of women older than 50 will suffer an osteoporosis-related bone fracture, and one-third of white women ages 65 and older will have a fracture of the spine in their lifetime.²⁰

Coronary artery disease
After menopause, a woman’s risk for coronary artery disease increases.²⁰ A decline in the natural hormone estrogen may be a factor in heart-disease increase among post-menopausal women. Estrogen is believed to have a positive effect on the inner layer of the artery wall, helping to keep blood vessels flexible.²²