Fertility and Pregnancy

Based on a study conducted by the National Institute of Environmental Health Sciences (NIEHS), a woman’s cycle of fertility is six days long – the five days before ovulation and ovulation day itself.  Pregnancy can be attained by making sure that the sperm is available when the egg is ready for fertilization during the monthly cycle.  During each normal menstrual cycle, an egg or ovum is usually released from one of the ovaries.  This is what is known as ovulation.

Ovulation happens about 14 days before the next menstrual cycle period.  The egg is swept into the funnel-shaped end of one of the fallopian tubes which is the usual site of fertilization.  The mucus in the cervix becomes more fluid and more elastic during ovulation.  This makes it possible for the sperm to enter the uterus rapidly.  In a matter of minutes, the sperm can move from the vagina, through the cervix into the uterus to the end of the fallopian tube.  The cells lining the fallopian tube facilitate the fertilization.

Fertilization results if a sperm penetrates the egg. Tiny hair-like cilia lining the fallopian tube propel the fertilized egg or the zygote through the tube towards the uterus.  The cells of the zygote divide repeatedly as it moves down the fallopian tube and enters the uterus in 3 to 5 days.  The cells continue to divide in the uterus and eventually develop into a fetus.

The egg degenerates and passes through the uterus with the next menstrual period if fertilization does not occur.  Pregnancy would involve more than one fetus when more than one egg is released and fertilized.  This usually results to fraternal twins.  Identical twins result when one fertilized egg separates into two embryos after it has begun to divide.