Maternal Inborn Errors of Metabolism in Pregnancy: A Pregnancy Registry Protocol

Women with inherited metabolic disorders are reaching child bearing age more often due to advances in early diagnosis and improved pediatric care. For many of these disorders, there is very little information in the literature to guide the counseling and treatment of these patients and their pregnancies.

The most information for the effects of an underlying inborn error of metabolism in pregnancy derives from the study of phenylketonuria (PKU). From the knowledge gained through the collection of information from multiple cases of pregnancy affected by PKU, important management issues were identified. For example, children born to mothers with an unrestricted diet were substantially more likely to have intellectual disability, microcephaly, and low birth weights than women who maintained a phenylalanine restricted diet. The excess phenylalanine poses long-term health risks to the developing fetus and now a vigilant metabolic approach is recognized as mandatory in women with PKU desiring pregnancy.

Compared to PKU, most or all other intermediary metabolic disorders have been understudied. For example, there are nine published cases of methylmalonic acidemia (MMA) in pregnancy and one case of cobalamin C deficiency in pregnancy, and review articles have reported the same cases. For other inborn errors of metabolism there is even less published or known. The paucity of publication of pregnancy in IEMs other than PKU may be due to the lack of organized research to address pregnancy management in metabolic disorders.

The objective of this study is to establish a pregnancy registry of women with inborn errors of metabolism other than PKU. We will collect management plans, baseline laboratory values, prenatal and postpartum course including metabolic and obstetrical issues, and fetal/neonatal outcomes. This study will also investigate reproductive issues including infertility and use of artificial reproductive technologies. A registry of this type will allow physicians and patients to report varying management and outcomes, both positive and negative, with the broader goal of delineating optimal maternal and fetal outcomes for these unique patient populations. Our registry data would also serve as a vehicle to disseminate management experience for all providers, recognizing that individual centers may not have sufficient experience to make accurate management decisions on their own.