Infertility is defined as a failure to conceive within one or more years of regular unprotected coitus. Primary infertility denotes those patients who have never conceived. Secondary infertility indicates previous pregnancy but failure to conceive subsequently within one or more years of unprotected regular intercourse. A healthy couple, on an average takes a year to achieve pregnancy. If the couple fails to conceive for two years, after regular sexual intercourse without contraception, they could be a case of infertility.

80 percent of the couples achieve conception if they so desire, within one year of having regular intercourse with adequate frequency (4–5 times a week). Another 10 percent will achieve the purpose by the end of second year. As such, 10 percent remain infertile by the end of second year.
Factors Responsible of Fertility are:

• The normal count of spermatozoa is 100 million/ml. The minimum count for fertility is 20 million/ml. The production of healthy spermatozoa is necessary to be deposited in vagina.
• The spermatozoa remain healthy and penetrate into the uterine cavity and into the uterine tubes.
• Production of ova is vital. The ovum finds its way into the uterine tube where it can be fertilized by a spermatozoon.
• The fertilized ovum migrates into the uterus and the endometrium should be hospitable for the spermatozoa for the implantation of fertilized ovum.

Causes of Infertility
The numerous reasons that lead to infertility can be broadly categorized to be related to the anatomy ( physiological causes) or due to some kinds of infections (pathological causes).
Physiological
Infertility is the rule prior to puberty and after menopause. But it should be remembered that the girl may be pregnant even before the menarche and pregnancy is possible within few months of menopause. Fertility is lower until the age of 16–17 years and after 35 years. Conception is impossible during pregnancy as the hormone Human Chorionic Gonadotrophin HCG is suppressed and hence no ovulation. During lactation, infertility is said to be relative. Inspite of the fact that the patient is amenorrhagic during lactation, ovulation and conception can occur. However, in fully lactating women (breast feeding 5–6 times a day and spending 60 minutes in 24 hours), pregnancy is unlikely up to 10 weeks postpartum.
Pathological
Conception depends on the fertility of both the male and female partner. It is also emphasized that the relative infertility of one partner may sometimes be counter balanced by the high fertility of the other.
Faults in the Female Ovarian Factors

• Anovulation and Oligo–ovulation (infrequent ovulation)
• Corpus Luteum Insufficiency (CLI)
• Lutinization of Unruptured Follicle (LUF)

Anovulation or Oligo–ovulation
In the absence of ovulation, conception cannot take place. This is quite frequent during adolescence or premenopausal period. Hypothalamic or Cortical factors
Pituitary Gonadal
Others Factors are

• Thyroid dysfunction.
• Substantial weight loss (anorexia nervosa).
• Diabetes mellitus.
• Adrenal hyperfunction.
• Pelvic endometriosis.

As there is no ovulation, there is no corpus luteum formation. In the absence of progesterone, there is no secretary endometrium in the second half of the cycle. The other features of ovulation are absent.

Corpus Luteum Insufficiency (CLI)
In this condition, there is inadequate growth and function of the corpus luteum. The life span of the corpus luteum is shortened to less than 10 days. There is insufficient secretion of progesterone and hence less secretary changes in the endometrium which hinders implantation.

Luteinized Unruptured Follicular Syndrome (trapped ovum)
In this condition the ovum gets trapped inside the follicle which gets matured. The cause is obscure but may be associated with pelvic endometriosis.

Tubal Factors
The impaired tubal function (tubopathy) includes defective ovum pick up, impaired tubal motility, loss of cilia (hair like processes inside the fallopian tubes) and partial to complete obstruction of the tubal lumen. Infections like tuberculosis, gonococcal or post–partum infection can cause bilateral blockage of the fallopian tubes.
Peritoneal Factors
In addition to adhesions that surround the fallopian tubes, endometriosis is an important cause of infertility by producing ovulatory dysfunction and is responsible for changed tubal motility.
Uterine Factors
The endometrium must be sufficiently accessible enough for effective implantation and growth of the fertilized ovum. The possible factors that hinder implantation are underdeveloped uterus, inadequate secretary endometrium, fibroid uterus, endometritis, uterine adhesions or congenital malformation of uterus.
Cervical Factors
Anatomic–Anatomic defects like congenital elongation of the cervix, second degree uterine prolapse and acute retroverted uterus prevents the sperm to enter. These conditions prevent the external os to bathe in the seminal pool. Pin hole os may at times be at fault, or the cervical canal may be obstructed by a polyp .
Physiologic–In this spermatozoa fail to penetrate the mucus due to fault in the composition of the cervical mucus. The mucus may be scanty following amputation, confiscation or deep cauterization of the cervix. The abnormal constituents include excessive, viscous or purulent discharge as in chronic infection of the cervix (cervicitis).
Vaginal Factors
Absence of vagina (partial or complete), transverse vaginal septum, septate vagina (where the vaginal canal is abnormally divided by a septum) or narrow introitus causing dyspareunia included in the congenital group. Infection of the vagina and purulent discharge may at times be the cause but pregnancy can take place in presence of vaginitis specific or non–specific.

Factors causing infertility in the male and female partners

• Anxiety and apprehension.
• Advancing age of the wife beyond 35 is related but spermatogenesis continues throughout life although ageing reduces the fertility in the male also.
• Infrequent intercourse, lack of knowledge of coital technique and timing of coitus to utilize the fertile period are very much common even amongst the literate couples.
• Apareunia and dyspareunia (Painful or difficult sexual intercourse).
• Use of lubricants during intercourse–which may be spermicidal.