Whether you conceive naturally or with the assistance of reproductive technology, you want to do everything possible to ensure the normal development and success of your pregnancy. Women who've undergone fertility treatment are often more conscious of the things that can go wrong with what was so difficult to achieve in the first place.

Many women routinely give up the use of substances that they worry will hurt their unborn baby, sometimes with, but sometimes without scientific proof of their harm. In fact, because it's difficult and even sometimes unethical to test research hypotheses with women who are pregnant, some of what is believed is based on less than solid evidence.

A few pregnant women will pare their lifestyles down to the bare minimum, for example, giving up cosmetics and toiletries that are suspected to have embryo-harming chemical ingredients. Many will stop pumping their own gasoline and many more (fortunately) will cease smoking cigarettes. Some will avoid eating certain foods and drinking alcohol.

While we know for certain that some of these life-enhancing (though not always essential) substances can indeed be toxic to pregnancy, many others are still a mystery. Caffeine has long been considered of concern of things to be avoided by pregnant women. Now, a new study published in the January 2008 American Journal of Obstetrics and Gynecology provides further clarity by demonstrating the impact of caffeine on pregnancy. The study concludes with strong evidence that women who drink 200 mg or more of caffeine per day, whether in coffee, tea, soda, or chocolate form, have twice the risk of miscarriage when compared to women who consume no caffeine. (200 milligrams is roughly equivalent to two or more cups of regular coffee or five 12-ounce cans of caffeinated soda.)

Many researchers believe that caffeine is harmful because it stresses the fetus’ immature metabolism. Caffeine has already been proven to cross through the placenta and it could, theoretically, have a negative impact on embryonic cell development and/or decrease blood flow in the placenta.

Women who plan their pregnancies and are aware of their time of conception inherently have a time-based advantage in their babies' favor. Though the “ why's” of embryo implantation or its failure are not fully understood, there are some areas that are a matter of choice and can be controlled by the mother-to-be.

With this latest information, we can add the reduction or elimination of caffeine intake to the list of things you can do to promote a successful pregnancy.

It can be hard to give up things we enjoy, but knowing that small sacrifices may add up to a healthier baby is plenty of motivation.