Maternal Phenylketonuria Syndrome (MPKU) can occur in infants born to mothers with PKU with poor metabolic control during pregnancy. Elevated phenylalanine (phe) acts as a teratogen to the developing fetus with consequences including intellectual disability, microcephaly, facial dysmorphism, growth retardation, and congenital heart disease. MPKU can be prevented if metabolic control is achieved by 8–10 weeks gestation. If control is not achieved, there is a significant risk for MPKU. Therefore, in women with poor metabolic control at time of pregnancy, establishing metabolic control quickly is important. Clinically, establishing metabolic control in women with PKU can present challenges. Social issues, psychological issues, and insufficient education about PKU play an important role in a patient’s inability to reinstitute this challenging diet. Maintaining phe levels within a range to allow for infant growth, while preventing toxicity, is challenging, particularly for those women who no longer follow the PKU diet. Gastrostomy tube placement is an option to deliver medical formula to women who are unable to restart diet due to severe nausea or palatability issues. Here we discuss two pregnancies in which a gastrostomy tube was placed to achieve metabolic control after other measures failed to reduce phe concentrations into the recommended range. For these two pregnancies, placement of the gastrostomy tube led to improvement in phe levels with normal infant outcomes including normal growth, head circumference, and heart structure.