Roux-en-Y gastric bypass (RYGB) alters the stomach and intestine in ways that reduce caloric intake and absorption. These changes can also decrease absorption of nutrients such as iron, vitamin B12, folate, vitamin D and calcium. As a result, human RYGB patients are counseled to take oral supplements after surgery. During pregnancy, adequate nutrient levels are necessary for supporting fetal development and growth, so females who become pregnant after RYGB may be more likely to demonstrate deficiencies in key nutrients that could directly affect their offspring.