Methylmalonic acidemia (MMA) in pregnancy: a case series and literature review.

INTRODUCTION: Women with inherited metabolic disorders, including those with previously life-limiting conditions such as MMA, are reaching child-bearing age more often due to advances in early diagnosis and improved pediatric care. Information surrounding maternal and fetal complications associated with the underlying disorders remains largely unexplored.
METHODS: Pregnancies affected by maternal MMA were ascertained through study 04-HG-0127 "Clinical and Basic Investigations of Methylmalonic Acidemia and Related Disorders" (clinicaltrials.gov identifier: NCT00078078) and via literature review. Prenatal and delivery records in study participants were reviewed.
RESULTS: Seventeen pregnancies were identified in women with isolated MMA, including three abortions, one termination, and 13 completed pregnancies [three cases with cblA (four pregnancies), four cases of mut- (one cobalamin responsive, three non-responsive), five cases with unknown type of MMA]. Seventeen percent (3/17) of the pregnancies resulted in a first trimester abortion, while 38.5% (5/13) of the completed pregnancies resulted in preterm deliveries. A cesarean delivery rate of 53.8% (7/13) was noted among the cohort. Fetal distress or nonreassuring fetal status was the indication for 57% (4/7) cesarean deliveries. One patient was reported to have metabolic crisis as well as episodes of mild hyperammonemia. Malformations or adverse outcomes in the progeny were not observed.
CONCLUSION: Although there have been a small number of pregnancies identified in women with MMA, the cumulative results suggest that the majority of pregnancies can be complicated by cesarean delivery and increased risk of prematurity. A pregnancy registry could clarify perinatal complications and define management approaches needed to ensure optimal maternal and fetal outcomes in this growing patient population.