There are few times in life when what a woman eats is more important than during pregnancy; not only does proper nutrition increase the chances of having a healthy baby, but it also helps ensure that the mother will be healthy. Unfortunately, there are many misconceptions about what a pregnant woman should or should not eat.

A common misconception involves how much weight a woman should gain during pregnancy. For years, women were told that they should virtually starve themselves to hold the weight gain to eight or 10 pounds. In reality, if you begin your pregnancy at or near ideal wright, you should gain an average of two to three pounds a month, for a total weight gain of 24 to 30 pounds. Of course, women who are overweight at the start of their pregnancy should gain less, and those who are very thin should gain more. if you plan to breast-feed your baby, you will find that you will lose the extra weight.

How did doctors get the idea that pregnant women should gain much weight? In the days when many women had rickets, a small baby stood a better chance of a normal birth despite the mother's deformed pelvis. During World War I in Germany, it was reported that women who went on a low-protein, low-calorie diet during pregnancy had a lower incidence of preeclampsia (a disease marked by high blood pressure, edema and protein in the-urine) and toxemia than women who ate a normal diet and gained more weight. German doctors began advocating low weight gain during pregnancy, and other Western obstetricians followed suit, even though there was no firm medical evidence that such a diet really was beneficial. Indeed, later studies showed that women who are undernourished during pregnancy hav e higher rate of toxemia and preeclampsia than women who eat a good diet.

What should you eat during pregnancy? In general, a pregnant woman needs the same foods as the rest of the population, only more so. The old adage of "a tooth for every child" is not necessarily true, but if a woman lacks adequate calcium in her diet, she will sacrifice the calcium reserves in her own skeleton and teeth to build her baby's bones and teeth. To ensure that both mother and baby get enough calcium, the diet should supply ample amounts of such high-calcium foods as milk and cheese; vitamin D, which is in enriched milk; phosphorus, found in dairy products, meat and fruits and vegetables; and fluoride, which should be supplied by your doctor or dentis if it is not already in your water supply.

Vitamin A also is important to the developing fetus, as are protein, the B vitamins, iron, folic acid, various minerals -- especially iodine, zinc and manganese -- and vitamin C.

Most of these nutrients can be obtained by eating a varied diet that includes foods that are fresh or lightly processed. However, obstetricians of ten prescsribe supplemental iron and folic acid. if you doctor decides you should have extra iron or other vitamins and minerals, he will recommend a supplement.

Current theories about weight gain do not mean you can gorge yourself on high-calorie sweets. You need to pack a great many nutrients into the calories that make up those 30 pounds. So cut down on sugar, candy, pastries and other fattening foods that have little or no nutritive value. Instead, be sure your daily diet includes plenty of milk, cheese and other dairy products, vegetables, fruits, whole-grain breads and cereals, and lean meats, fish and poultry. to prevent constipation, a common problem during pregnancy, eat foods that are high in fiber or roughage (whole-grain breads and cereals and plenty of fresh fruits and vegetables), and drink lots of fluids. As always, exercise is important.

Unless your doctor recommends a salt-restricted diet, you can eat a moderate amount of salt during pregnancy. but it's wise to avoid heavily salted foods such as potato chips, salted nuts and anchovies.

More and more studies show that both smoking and alcoholic beverages are harmful to the developing fetus. If you smoke, we strongly urge you to stop entirely. If you drink in a social situation, limit your intake to one or two small drinks, such as wine.

If you follow this common-sense approach to proper nutrition during pregnancy, you will enhance your own health and your baby's without constant worry.