Once you decide you want to have a baby, it is natural to hope it happens quickly. You probably know somebody who got pregnant very easily, and you think you should too. You may get pregnant right away, but you might not. It’s important to know what is considered normal, so you don’t worry if there is no cause for concern.

90% of couples will conceive within 12 to 18 months of trying.

Infertility is defined by doctors as the inability to get pregnant (conceive) after 12 months of frequent, unprotected sex (intercourse), if you are less than 35 years old

If you are 35 years of age or older, doctors will start evaluating your fertility after six months of unsuccessful attempts at pregnancy. If you are having regular menstrual periods, you are probably ovulating regularly. You need to know that you are the most fertile in the middle of your cycle, between periods. That is when you release an egg. You and your partner should have frequent sex on a number of days in the middle of your cycle. You can use an over-the-counter fertility kit to find out when you are ovulating. You should not use any lubricant, and the standard wisdom is that you should not get up immediately after having sex.

Somewhere around 25% of couples will be pregnant at the end of the first month of trying. About 50% will have conceived in 6 months. Between 85 and 90% of couples will have conceived at the end of a year. Of those that have not conceived, some still will, without any specific help. Many of them will not.

Approximately 10 to 15% of American couples are, by definition, infertile. Evaluation of infertility is usually not done until a full year has gone by. This is because most people will conceive by then. The evaluation of infertility can be embarrassing for some people, expensive, and uncomfortable. If started too early, infertility evaluation will lead to testing of people who do not need it. When the woman is 35 years of age or older, an evaluation should begin if conception does not occur in six months.

You need to remember that you cannot completely plan pregnancy.

All this is assuming that you have no known, serious medical problems that will prevent you from ovulating, that you have sex when you are fertile, and that your partner does not have any known, serious medical problems that can affect his ability to produce sperm.

Anyone with a past history of infertility with a previous partner or other medical problems known to be associated with infertility should be evaluated earlier. Some examples of problems a woman might have include not ovulating, which might be suspected because of a lack of regular periods, any hormonal problems, like an underactive or overactive thyroid, having had cancer, and having had cancer treated. Men who have had cancer treatment may also be infertile. Hormonal problems and some illnesses like mumps can affect a man’s ability to father a child.

So if you and your partner are well as far as you know and having regular sex during the middle of your cycle, and you are not over age 35, you should give yourselves quite a number of months before you start to worry.

You need to remember that you cannot completely plan pregnancy. While it might take you six months or more to get pregnant, it might not, and you could become pregnant the first time you try.