the developing fetus receives its nutrition from the mother's blood. therefore high-fat diets and some vegetarian diets are discouraged during pregnancy because they may not provide all the nutrition needed for the developing fetus. bulimia anorexia nervosa and other eating disorders in the mother need to be addressed and treated. weight reduction diets are avoided. excess intake of sugar alcohol megavitamins and caffeine should also be avoided. because a "safe" amount of caffeine has never been confirmed to date it is best to avoid caffeine entirely. women who feel strongly that they need some coffee are advised to drink no more than one cup per day. there is no proof that one to two cups of coffee daily cause pregnancy complications. listeria is a type of bacteria found in contaminated food that can cause miscarriage and other problems to a fetus. because of the danger of getting a listeria infection pregnant women should avoid unpasteurized milk soft cheeses cold cuts and undercooked or raw animal foods. in addition fruits and vegetables should be washed completely prior to consumption. phenylketonuria is an inherited disease that affects the utilization of a certain protein component in foods. this disorder can be detected by a blood test. mothers with phenylketonuria may give birth to developmentally disabled children unless their diets are strictly controlled to exclude phenylalanine. megavitamins contain double or even triple the recommended daily allowances of vitamins and minerals. high doses of vitamin a have been implicated in producing birth defects. the better idea is to avoid megavitamins and instead follow the recommendation that has proven benefit: take a prenatal vitamin containing folic acid. folic acid intake in the mother prior to and during pregnancy has been shown to reduce the risk of birth defects involving the brain and spinal cord. the u. s. public health service recommends folic acid for all women of childbearing capacity. studies have shown that if folic acid is begun at least four weeks prior to conception the risk of birth defects of the spinal cord and skull can be reduced by more than 70%. in women with or even without a history of having infants with birth defects of the spinal cord or skull folic acid should be taken one month before conception and continued through the 12th week of pregnancy. in fact continuing prenatal vitamins through pregnancy and even through nursing is probably wise. these prenatal vitamins are available over the counter. if a particular brand makes you feel nauseated simply switch to another brand or try taking the vitamin at night. because of the risks of mercury poisoning and nervous system damage in the fetus from contaminated fish pregnant women are advised to eliminate consumption of certain types of fish that are known to be high in mercury including shark swordfish tilefish and king mackerel. tuna steaks made from large tuna may also have high mercury levels. canned tuna is made from smaller fish that typically have lower levels of mercury than larger fish.
how can diet and nutrition affect early pregnancy?