Infertility is defined as trying to get pregnant (with frequent intercourse) for at least a year with no success. Female infertility, male infertility or a combination of the two affects millions of couples in the Nigeria. An estimated 10 to 18 percent of couples have trouble getting pregnant or having a successful delivery.
Infertility results from female factors about one-third of the time and male factors about one-third of the time. The cause is either unknown or a combination of male and female factors in the remaining cases.
Female infertility causes can be difficult to diagnose. There are many available treatments, which will depend on the cause of infertility. Many infertile couples will go on to conceive a child without treatment. After trying to get pregnant for two years, about 95 percent of couples successfully conceive. 

 CausesEach of these factors is essential to become pregnant:1. You need to ovulate.
To get pregnant, your ovaries must produce and release an egg, a process known as ovulation. Your doctor can help evaluate your menstrual cycles and confirm ovulation.
Your partner needs sperm. For most couples, this isn't a problem unless your partner has a history of illness or surgery. Your doctor can run some simple tests to evaluate the health of your partner's sperm.
2. You need to have regular intercourse.
You need to have regular sexual intercourse during your fertile time. Your doctor can help you better understand when you're most fertile.
3. You need to have open fallopian tubes and a normal uterus.
The egg and sperm meet in the fallopian tubes, and the embryo needs a healthy uterus in which to grow.For pregnancy to occur, every step of the human reproduction process has to happen correctly. The steps in this process are:a. One of the two ovaries releases a mature egg.
b. The egg is picked up by the fallopian tube.
c. Sperm swim up the cervix, through the uterus and into the fallopian tube to reach the egg for fertilization.
d. The fertilized egg travels down the fallopian tube to the uterus.
e. The fertilized egg implants and grows in the uterus.In women, a number of factors can disrupt this process at any step. Female infertility is caused by one or more of the factors below.1. Ovulation disordersOvulation disorders, meaning you ovulate infrequently or not at all, account for infertility in about 1 in 4 infertile couples. Problems with the regulation of reproductive hormones by the hypothalamus or the pituitary gland, or problems in the ovary, can cause ovulation disorders.2. Premature ovarian failure. Also called primary ovarian insufficiency, this disorder is usually caused by an autoimmune response or by premature loss of eggs from your ovary (possibly from genetics or chemotherapy). The ovary no longer produces eggs, and it lowers estrogen production in women under the age of 40.3. Too much prolactin. The pituitary gland may cause excess production of prolactin (hyperprolactinemia), which reduces estrogen production and may cause infertility. Usually related to a pituitary gland problem, this can also be caused by medications you're taking for another disease.4. Benign polyps or tumors (fibroids or myomas) are common in the uterus. Some can block fallopian tubes or interfere with implantation, affecting fertility. However, many women who have fibroids or polyps do become pregnant.
Endometriosis scarring or inflammation within the uterus can disrupt implantation.Symptoms
the main symptom of infertility is the inability to get pregnant. A menstrual cycle that's too long (35 days or more), too short (less than 21 days), irregular or absent can mean that you're not ovulating. There may be no other outward signs or symptoms.