Although manufacturers suggest that such products are safe for pregnant women, the pregnancy risk classification for the most common active ingredients in antiperspirants is set at category C (Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks). Studies have shown that a small amount of aluminum is absorbed through the skin when using antiperspirants. Other studies have shown that this uptake is less than the amount of aluminum absorbed from the diet. Even if the amount absorbed is low, women who are pregnant or nursing should avoid frequent and long-term use of antiperspirants that contain of aluminum.