Most common reasons include,

• The hypothalamus may not secrete gonadotropin-releasing hormone, which stimulates the pituitary gland to produce the hormones that stimulate the ovaries and stimulate ovulation (luteinizing hormone and follicle-stimulating hormone)
• The pituitary gland may produce too little luteinizing hormone or follicle-stimulating hormone
• The ovaries may produce too little estrogen
• The pituitary gland may produce too much prolactin, a hormone that stimulates milk production. High levels of prolactin (hyperprolactinemia) may result in low levels of the hormones that stimulate ovulation. Prolactin levels may be high because of a pituitary gland tumor (prolactinoma), which is almost always noncancerous
• Other glands may malfunction. For example, the adrenal glands may overproduce male hormones (such as testosterone), or the thyroid glands can overproduce or underproduce thyroid hormones, which help keep the pituitary gland and ovaries in balance

Common causes of ovulation disorders include,

• Obesity
• Polycystic Ovarian Syndrome
• Too low body weight
• Extreme exercise
• Hyperprolactinemia
• Premature ovarian failure
• Perimenopause, or low ovarian reserves
• Thyroid dysfunction (hyperthyroidism)
• Extremely high levels of stress

Because infertility is a complex disorder, treatment involves significant financial, physical, psychological and time commitments. Although some women need just one or two therapies to restore fertility, it's possible that several different types of treatment may be needed.

Some of the common fertility drugs prescribed by doctors include,

• Clomiphene citrate is taken orally and stimulates ovulation by causing the pituitary gland to release more FSH and LH, which stimulate the growth of an ovarian follicle containing an egg.
• Injected Gonadotropins stimulate the ovary directly to produce multiple eggs. Human gonadotropins contain follicle-stimulating hormone and sometimes luteinizing hormone. These hormones stimulate the follicles of the ovaries to mature and thus make ovulation possible. Follicles are fluid-filled cavities, each of which contains an egg. Ultrasonography can detect when the follicles are mature. Then, the woman is given an injection of a different hormone, human chorionic gonadotropin, to stimulate ovulation. Human chorionic gonadotropin is produced during pregnancy and is similar to luteinizing hormone, which is normally released in the middle of the menstrual cycle. Or, a gonadotropin-releasing hormone (GnRH) agonist can be used to stimulate ovulation, especially in women at high risk of ovarian hyperstimulation syndrome. GnRH agonists are synthetic forms of a hormone produced by the body (GnRH).When human gonadotropins are used appropriately, more than 95% of women treated with them ovulate, but only 50 to 75% of those who ovulate become pregnant. About 10 to 30% of pregnancies in women treated with human gonadotropins involve more than one fetus, primarily twins.
• Metformin is used when insulin resistance is a known or suspected cause of infertility, usually in women with a diagnosis of PCOS. Metformin helps improve insulin resistance, which can improve the likelihood of ovulation.
• Letrozole belongs to a class of drugs known as aromatase inhibitors and works in a similar fashion to clomiphene. Letrozole may induce ovulation. However, the effect this medication has on early pregnancy isn't yet known, so it is not used for ovulation induction as frequently as others.
• Bromocriptine is a dopamine agonist, may be used when ovulation problems are caused by excess production of prolactin (hyperprolactinemia) by the pituitary gland.

There are however, plenty of side-effects associated with such fertility drugs and hence one needs to take them only after expert advice,

• Pregnancy with multiples, like chances of giving birth to twins as well as triplets. Generally, the more fetuses one is carrying, the greater the risk of premature labor, low birth weight and later developmental problems. Sometimes adjusting medications can lower the risk of multiples, if too many follicles develop.
• Ovarian hyperstimulation syndrome (OHSS): Injecting fertility drugs to induce ovulation can cause OHSS, which causes swollen and painful ovaries. Signs and symptoms usually go away without treatment, and include mild abdominal pain, bloating, nausea, vomiting and diarrhea. If one becomes pregnant, however, the symptoms might last several weeks. Rarely, it's possible to develop a more-severe form of OHSS that can also cause rapid weight gain, enlarged painful ovaries, fluid in the abdomen and shortness of breath.
• Long-term risks of ovarian tumors: Most studies of women using fertility drugs suggest that there are few if any long-term risks. However, a few studies suggest that women taking fertility drugs for 12 or more months without a successful pregnancy may be at increased risk of borderline ovarian tumors later in life.
• Women who never have pregnancies have an increased risk of ovarian tumors, so it may be related to the underlying problem rather than the treatment. Since success rates are typically higher in the first few treatment cycles, re-evaluating medication use every few months and concentrating on the treatments that have the most success appear to be appropriate.

Eating a healthy, balanced diet along with getting adequate amount of rest and keeping stress at bay are some of the most basic things one can do in order to ensure the best of reproductive health. Some cases might also need laproscopic or tubal surgery while others may intra-uterine insemination of IVF to cure infertility.