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Fertility is the ability to conceive through sexual intercourse between a man and a woman, or through methods such as assisted reproductive technology (ART).

Under normal circumstances, a woman’s pituitary gland (endocrine gland about the size of a pea that sits at the base of the brain) sends a signal to the ovaries to prepare an egg for ovulation each month. The pituitary hormones involved in this process are follicle-stimulating hormone (FSH) and luteinizing hormone (LH). After a dominant follicle has developed from increasing FSH stimulation, then usually at midcycle a surge in LH will send a signal to the ovarian follicle to release an egg (ovulate). Ovulation on average occurs around day 14 of the menstrual cycle, although the exact timing varies among women and from month to month.

After the egg is released, it is picked up by the fallopian tube where it remains viable for about 24 hours. For conception to occur, sperm enters the body usually through sexual intercourse. Then, it must travel through the vagina, into the uterus and up into the fallopian tube to unite with the egg. Sperm are viable for up to 72 hours.

If fertilization occurs, the fertilized egg (zygote) travels down to the uterus and implants itself into the uterine wall, which develops into an embryo and then a fetus over a 40-week (approximately nine-month) period.

Though conception may seem straightforward, there are hundreds of variables that may influence the reproductive process. These variables may either prevent conception or result in an unplanned pregnancy.

Some women practice natural family planning, which is a method of determining the best times to conceive. This involves several techniques for determining when ovulation occurs, including:

• Keeping a fertility calendar. Women chart their menstrual cycles on a calendar by noting the days their period begins and ends. In women with a 28-day cycle, ovulation occurs about 14 days after the day the last period began. However, tracking ovulation can be difficult because numerous factors such as stress and illness can impact the timing of ovulation.
  
  
• Using an ovulation monitoring kit (this tests urine for the presence of hormones associated with ovulation). While these kits provide an accurate way to detect the time of ovulation, they can be costly, ranging from $20 to $50 apiece. They may also lead couples to time sex to occur too late after ovulation for conception.
  
  
• Tracking basal body temperature (temperature when the body is at rest). Ovulation may cause a jump in body temperature, usually between 0.5 to 1.6 degrees Fahrenheit (17.5 to 16.9 degrees Celsius). Women are most fertile during the two to three days prior to the temperature rise. Body temperature can be measured using an oral thermometer that can be purchased at a pharmacy. Women using this technique should take their temperature at the same time each morning (before getting out of bed) and identify patterns that emerge over the course of a month. Although this is a simple method, it may be difficult to identify ovulation because the temperature rise may be too subtle to detect or may occur after ovulation has already happened.
  
  
• Monitoring changes in the cervical mucus. Right before ovulation, there is an increase in a clear, slippery vaginal secretion that resembles raw egg whites. After ovulation, it becomes cloudy or sticky, or disappears. Although the change in the secretion is an accurate way to detect ovulation, judging the appearance of the secretion can be difficult.

Some women also consider making lifestyle changes that have been identified as impacting fertility. Among them are:

• Having regular sex. Couples trying to conceive should have sex frequently (at least two or three times a week). Around the time a woman is ovulating, the frequency should increase to once a day.
  
  
• Maintaining a healthy lifestyle. Maintaining a normal weight, exercising regularly and eating a healthy and varied diet can help a woman conceive. They are also important practices during pregnancy. A physician, typically an obstetrician, can help identify lifestyle changes that improve chances of conceiving and a healthy pregnancy.
  
  
• Taking vitamins. Folic acid (vitamin B-9) plays an important role in a baby’s development. Taking a prenatal vitamin or folic acid supplement at least one month before conception through the first trimester of pregnancy can reduce the risk of some birth defects, especially neural tube defects such as spina bifida.
  
  
• Quitting smoking. Women should quit smoking because tobacco changes the cervical mucus, which may prevent sperm from reaching the egg. Quitting smoking may also decrease the risk of miscarriage.
  
  
• Avoiding alcohol. Women should avoid drinking alcohol if they are trying to conceive or are pregnant.
  
  
• Avoiding certain medications. Some medications can make conceiving more difficult. Patients should consult with a physician before taking any medication to determine whether it will impact conception as well as pregnancy.