Ovulation

• A woman is only fertile around ovulation, when her body releases an egg from the ovary. Conception is possible if intercourse occurs during the period of five days before ovulation to two days after. This is because sperm can survive inside a woman's body for up to five days. Although the egg can survive no more than 24 hours after ovulation, it is possible for a woman to release more than one egg within that period. Although these are generous estimates, they give women about seven days to get pregnant during each cycle.
  
  Conception would be much easier to achieve if women knew exactly when they were ovulating. Most people falsely believe that a normal menstrual cycle lasts 28 days and that ovulation occurs on day 14. But cycles vary greatly among women and even from one month to the next. Without studying and understanding her own cycles, a woman can only guess at when she's ovulating, making her chances of conceiving much lower.
  
  

Sperm

• Even when intercourse occurs around ovulation, a man's sperm have a long journey to make before fertilizing the egg. The acid level of the vagina kills some sperm, the cervical mucus stops others from moving along, and the remaining ones must travel 7 inches to get to the fallopian tubes. Of the millions of sperm released during ejaculation, only a few dozen will make it to the egg.
  
  

Implantation

• After the egg is fertilized it must travel down the fallopian tubes and implant into the wall of the uterus, which is technically when pregnancy begins. Occasionally, however, the egg will fail to implant, in which case the lining of the uterus will slough off as usual and the woman will probably have what seems like a normal period.
  
  

Pregnancy Loss

• Even if a fertilized egg successfully implants, miscarriage is common in the early weeks. Anywhere from 30 to 50 percent of fertilized eggs are lost even before a woman finds out she's pregnant and 15 to 20 percent of known pregnancies result in miscarriage--more than 80 percent occurring before 12 weeks of pregnancy.
  
  

Increasing your Chances

• To increase your likelihood of becoming pregnant, you should begin to track your menstrual cycle to learn when you are ovulating. This can be done by charting your basal body temperature (right after waking) and noting cervical mucus over a number of cycles. You are usually most fertile two or three days before your basal body temperature spikes and when cervical mucus is clear, slippery and stretchy.