Most of the couples get pregnant naturally by having sexual intercourse. But this is not same in 1 out of 6 couples. They may need assisted reproductive technology to get pregnant.
Two simple techniques practiced today are, artificial insemination and the other one is in-vitro fertilization.
Until 19th century, it was considered that a women can conceive only through sexual intercourse. Now there are many other methods for a woman to get pregnant if she cannot conceive naturally and one of such methods is in-vitro fertilization.
What is fertilization all about?
Fertilization is a process where in a sperm and the egg come together, get fused and develop into an embryo, and eventually into a new individual. This can be achieved either by sexual intercourse, by artificial insemination or by in-vitro fertilization.
When a couple fails to get pregnant by sexual intercourse or by artificial insemination, the gynecologist may advice her to try in-vitro fertilization
Want to know, what in-vitro fertilization (IVF) is all about?
Here the fertilization is done outside the body. In this fertilization technique, several eggs are removed out of the body for fertilization in the laboratory. One or two of these fertilized eggs, now known as an embryo, are returned back to the uterus in the hope that they will implant and result in pregnancy.
Women planning for IVF are given special reproductive hormones to stimulate the production of several eggs in the ovaries .At a time around 5-12 eggs are expected to grow in the ovary.  Final maturation of the egg is encouraged by the administration of further hormones.
After 3 days, the fluid with egg is drawn out through the needle into a test tube one by one. This is usually performed with a light sedation in a short outpatient procedure using an ultrasound technique to check the proceedings.  This procedure takes over 10- 40 minutes. The egg is now transferred to the laboratory for a thorough examination for getting a good quality egg.  These eggs are washed with the solution graded for the maturity of the egg, and placed in a CO2 incubator for 6 hours. Now the egg is ready for fertilization.
Fertilization, here, it is achieved by two methods, either the eggs are mixed with the sperm sample collected from the male partner or a selected healthy sperm from the partner will be injected into the egg.
The sperms are washed and concentrated before mixing with the egg. This mixture of sperm and eggs are left in the incubator at 35 for 24 hours, so that fertilization can take place. During this time only one out of several sperms will be successful to penetrate inside the egg.
After two or three days, when the fertilized egg becomes an embryo, it will be transfered into the uterus for further development. A healthy embryo will have around eight cells. The embryo is transferred into the uterus by means of a thin, flexible tube, where it gets implanted on the wall of the uterus and result in pregnancy.
The unused embryos can be preserved by freezing them at a temperature of -196  for further use for many years
A consultation and thorough examination is required for every individual to find out the most appropriate treatment method to achieve the highest amount of success.   
Female fertility rate decreases after the age of 35. So infertile couples are advised not delay in seeking appropriate medical advice.