Causes for male infertility:
(i) Undescended tests and swollen veins in scrotum
(ii) Underdeveloped testes
(iii) Tight clothing increases the temperature in scrotum and affect sperm production.
(iv) Autoimmune response against own sperm.
(v) Usage of alcohol, tobacco, marijuana drugs etc.
Causes for female infertility:
(i) Malformation of cervix or fallopian tubes.
(ii) Inadequate nutrition at puberty.
(iii) Low body fat (anorexia = psychological eating disorder due to fear of gaining weight) .
(iv) Pelvic Inflammatory Disease (PID), uterine disorders, endometriosis.
(v) underdeveloped ovaries.
(vi) Developing antibodies against sperm.
Common Causes for both the sexes:
(i) Tumours in pituitary or sex organs
(ii) Inherited mutation of hormone synthesizing genes
(iii) Long term stress
(iv) Ingestion of toxins (Cadmium) & drugs
(v) Injuries to gonads
(vi) Ageing

Intrauterine Devices (IUDs) are inserted by medical experts in the uterus through the vagina. These devices are available as copper releasing IUDs, hormone-releasing IUDs and nonmedicated IUDs. IUDs increase phagocytosis of sperm within the uterus. IUDs are the ideal contraceptives for females who want to delay pregnancy. It is one of the popular methods of contraception in India and has a success rate of 95 to 99%.
Copper releasing IUDs differ from each other by the amount of copper. Copper IUDs such as Cu T-380 A, Nova T, Cu 7, Cu T 380 Ag, Multiload 375, etc. release free copper and copper salts into the uterus and suppress sperm motility. They can remain in the uterus for five to ten years.
Hormone-releasing IUDs such as Progestasert and LNG - 20 are often called as intrauterine systems (IUS). They increase the viscosity of the cervical mucus and thereby prevent sperms from entering the cervix.
Non-medicated IUDs are made of plastic or stainless steel. Lippes loop is a double S-shaped plastic device.

Natural method is used to prevent meeting of sperm with ovum. i.e., Rhythm method (safe period), coitus interruptus, continuous abstinence and lactational amenorrhoea.
a. Periodic abstinence/rhythm method: Ovulation occurs at about the 14th day of the menstrual cycle. Ovum survives for about two days and sperm remains alive for about 72 hours in the female reproductive tract. Coitus is to be avoided during this time.
b. Continuous abstinence is the simplest and most reliable way to avoid pregnancy is not to have coitus for a defined period that facilitates conception.
c. Coitus interruptus is the oldest family planning method. The male partner withdraws his penis before ejaculation, thereby preventing deposition of semen into the vagina.
d. Lactational amenorrhoea : Menstrual cycles resume as early as 6 to 8 weeks from parturition. However, the reappearance of normal ovarian cycles may be delayed for six months during breast-feeding. This delay in ovarian cycles is called lactational amenorrhoea. It serves as a natural, but an unreliable form of birth control. Suckling by the baby during breast-feeding stimulates the pituitary to secrete increased prolactin hormone in order to increase milk production. This high prolactin concentration in the mother's blood may prevent menstrual cycle by suppressing the release of GnRH (Gonadotropin Releasing Hormone) from hypothalamus .and gonadotropin secretion from the pituitary.

A collection of procedures, which includes the handling of gametes and/or embryos outside the body to achieve a pregnancy as known as Assisted Reproductive Technology. It increases the chance of pregnancy in infertile couples. ART includes intra-uterin insemination (IUI), in vitro fertilization, (IVF) Embryo transfer, (ET), Zygote intra-fallopian transfer (ZIPT), Gamete intrafallopian transfer (GIFT), Intra-cytoplasmic, sperm Injection (ICSI), .Preimplantation genetic diagnosis, oocyte and sperm donation and surrogacy.
(i) Intra-cytoplasmic sperm injection (ICSI): In this method only one sperm is injected into the focal point of the egg to fertilize. The sperm is carefully injected into the cytoplasm of the egg. Fertilization , occurs in 75 - 85% of eggs injected with the sperms. The zrgote is allowed to divide to form an 8 celled blastomere and then transferred to the uterus to develop a productive pregnancy.
(ii) Surrogacy: Surrogacy is a method of assisted reproduction or agreement whereby a woman agrees to carry a Pregnancy for another person, who will become the newborn child's parent after birth. Through in vitro fertilization (IVF), embryesz are created in a lab and are transferred into the surrogate mother's uterus.

Inability to conceive or produce children even after unprotected sexual cohabitation is called infertility. That is, the inability of a man to produce sufficient numbers or quality of sperm to impregnate a woman or inability of a woman to become pregnant or maintain a pregnancy. The causes for infertility are tumours formed in the pituitary or reproductive organs, inherited mutations of genes responsible for the biosynthesis of sex hormones, malformation of the cervix or fallopian tubes and inadequate nutrition before adulthood. Long-term stress damages many aspects of health especially the menstrual cycle. Ingestion of toxins (heavy metal cadmium), heavy use of alcohol, tobacco and marijuana, injuries to the gonads and aging also cause infertility.
Other causes of infertility:
(i) Pelvic inflammatory disease (PID), uterine fibroids and endometriosis are the most common causes of infertility in women.
(ii) Low body fat or anorexia in women. i.e. a psychiatric eating disorder characterised by the fear of gaining weight.
(iii) Undescended testes and swollen veins (varicocele) in scrotum. Tight clothing in men may raise the temperature in the scrotum and affect sperm production.
(iv) Under developed ovaries or testes.
(v) Female may develop antibodies against her partner's sperm.
(vi) Males may develop an autoimmune response to their own sperm.