If you are 20-25 years of age and recently married and both with good health and fertility, you need not plan for a baby immediately. However you should know that your fertility is not permanent. With increase in age your quantity and quality of eggs and quality of sperms will decline. Add an unhealthy lifestyle to that and this decline will accelerate as your years add on.

Whether you are recently married and not planning a family immediately or have been married for 3-4 years and thinking of having a baby, or if you have been trying to start a family without success, here’s what we would advise you to do:

Age of Couples Healthy with no infertility factor in husband or wife (normal cycles, Sperms quality normal) One or more infertility factors in any one or both the partners (Irregular cycles/Abnormal semen parameters)
20-25 You have time till 26-27 years of age. You may wait for a couple of years but before you try naturally, we suggest you book a Pre-Conception counseling to get tips on how to lead a healthy lifestyle for the next few years to maintain your fertility health.

A basic evaluation (USG TVS and semen analysis) after 2-3 years may be good.
You should go for a Pre-Conception Counseling to understand your chances and how much time you may have to conceive naturally without IVF.
25-30 Do not delay. If you are ready to have a baby, Book a Natural conception counseling session and start trying naturally for a year. Take a Natural conception counseling appointment, start trying for 6 months. If you do not succeed go for a TI protocol for three months. If that fails too, discuss with your fertility expert to know what your treatment options are.
30-35 Start a Timed Intercourse cycle with expert guidance immediately. If that fails, IUI may be your next option. Take an appointment with a Fertility specialist, who would evaluate both the partners and suggest the best possible mode of treatment.
>35 You don’t have time to lose. If your ovarian reserve is good, You may be able to conceive by TI or else IUI. Your chance of having a second child naturally however would be slim. You might have to opt for an IVF pregnancy the second time around. If the Ovarian reserve is good it may be still possible for you to conceive by IVF treatment.

For A "TWO CHILD" Family - Plan Earlier

There was a very interesting study done in France in 2014. In order to have a chance of at least 90% to realize a one child family, couples should start trying to conceive when the female partner is 35 years or age or younger, if IVF is an acceptable option. For two children, the latest starting age is 31 years. Without IVF, couples should start not later than 32 years for a one child family and at 27 years for a two child family.