Almost everyone has helpful advice to offer when you’re trying to become pregnant. Should you listen to it all?

Probably not.

Most people don’t know nearly as much as they think they do about this subject, according to one survey.

The 2006 survey, conducted by the American Fertility Association, revealed that women in this country don’t know many of the basic facts about their own fertility and reproductive health.

The survey polled 12,382 women, who were asked 15 questions on different fertility issues. Just one participant in the study was able to answer all 15 questions correctly.

One of questions asked was at which age a woman's fertility begins to wane. A woman’s ability to conceive starts decreasing in her late twenties and continues with each passing year. There are two reasons for this:

1. Women are born with their complete supply of eggs — approximately seven million. By the time the average female enters puberty, she only has about 250,000-300,000 of that supply left. That’s because during each menstrual cycle, one egg matures­ and is released, but many others are not. So if a women starts with seven million eggs and ovulates 400 times, statistically speaking, it is inevitable that the supply will run out.

2. Eggs age in the same manner as the rest of the body. As eggs get older, they have a greater incidence of chromosomal abnormalities that increase the chances of miscarriage.

The media has publicized stories about women, especially celebrities, in their late thirties and forties who conceive and deliver healthy babies. However, the likelihood of that occurring without medical intervention declines with each passing year.

Women under age 30 have 20 to 30 percent chance of becoming pregnant in any one cycle. By the time they reach 40, their chances drop to about 5 percent.

A man’s fertility also is subject to the ravages of time. Men fifty and older typically find a decline in the quality of their sperm. In addition, they may experience a slight drop in testosterone levels and a shrinking libido.

Given these eventualities, it is important to maximize each attempt at conception. Dr. Sessions Cole, chief medical officer and director of Newborne Medicine at St. Louis Children's Hospital, believes both men and women need to follow a few simple guidelines or what he refers to as “pre-pregnancy planning” in order to get the desired results.

A couple is officially having trouble conceiving if they’ve tried for a year without success. But even if that is the case, Cole said couples should try not to get discouraged.

“Couples who are emotionally over-invested in getting pregnant have the hardest time,” he said. “That’s because the stress impacts on the internal factors that affect whether or not conception will be successful.”

He said young couples often think pregnancy is like buying a car.

“You see what you want, you put down your money and you drive off. It ain’t that easy. It’s an inappropriate expectation to think you can become pregnant after stopping birth control and trying for three months.”

The Man’s Role

He said maximizing the chance for pregnancy is as much the father’s responsibility as it is the mother’s, and that any discussion of this issue should begin with what the father can do.

Cole noted that, in the past, a fair amount of emphasis was placed on the mother’s role at the expense of the father’s contribution to becoming pregnant. But in recent years, the tide has turned and becoming pregnant has come to be viewed as a joint effort.

Men should avoid exposure to any environmental toxins like tobacco, alcohol, and pesticides or organic solvents, which can sometimes be found on the job.

In the case of the latter, while some exposure may be inevitable, a man can limit his risk by following the OSHA-mandated safety standards for this type of exposure such as wearing appropriate personal protective equipment, as well as showering and changing into street clothes before leaving the job site.

Men should also examine any drugs they are taking. Most people know that illegal drugs like marijuana and cocaine. Anabolic steroids also interfere with sperm production.

The American Fertility Association cautions men to avoid sulfasalazine, used in medications for IBS, Crohn’s and colitis; cimetidine used in ulcer medications; and spironolactone, used in hypertension prescriptions.

If you are currently taking one of these drugs and are planning to conceive, talk to your doctor about a prescription change.

What Women Can Do

The first step in a woman’s pre-pregnancy planning is to be sure that her physical condition is optimized.

If her Body Mass Index (BMI) is too light, her ovulatory cycle won’t be regular. Having too high of a BMI also presents a problem.

Cole said evidence shows that from the time of fertilization to the time the egg is implanted in the womb, conditions in the mother’s internal environment influence whether the implantation will be successful or not.

Women with high BMIs have differences in their internal environments in that time after fertilization that aren’t optimal for implantation.

Women also need to steer clear of alcohol and tobacco, and be aware of the influence of any medications they’re taking.

The American Fertility Association says prescription psychotropics, drugs that alter emotion or behavior, can interfere with ovulation. Non-prescription anti-inflammatory drugs taken at the time of ovulation can interfere with embryo implantation. Women on these types of medications should talk to their doctor about alternatives.

Cole recommends that women start taking pre-natal vitamins rich in folic acid daily two to three months before trying to conceive. This will reduce the risk of brain and spinal chord abnormalities and increases your chances of success conception.

Both men and women should eat right and exercise to ensure optimal physical condition. But Cole cautioned women not exercise to the point of lowering their BMI too much.

Foxnews.com health writer Maria Esposito contributed to this report.

Click here to check out Dr. Manny's book The Check List (Harper Collins, 2007), from which this article was excerpted.

Dr. Manny Alvarez is the managing editor of health news at FOXNews.com, and is a regular medical contributor on the FOX News Channel. He is chairman of the Department of Obstetrics and Gynecology and Reproductive Science at Hackensack University Medical Center in New Jersey. Additionally, Alvarez is Adjunct Professor of Obstetrics and Gynecology at New York University School of Medicine in New York City.

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Dr. Manny Alvarez serves as Fox News Channel's Senior Managing Editor for Health News. Prior to this position, Alvarez was a FNC medical contributor. Click here more information on Dr. Manny's work with Hackensack University Medical Center. Visit AskDrManny.com for more.