The impact of maternal ketonuria on fetal test results in the setting of postterm pregnancy

OBJECTIVE: The aim of this study was to determine whether ketonuria, a comm only assessed urinary marker of maternal starvation and dehydration, is ass ociated with abnormal fetal test results in the setting of postterm pregnan cy. STUDY DESIGN: During a 4-year period (January 1993-December 1996), a total of 3655 visits for antepartum maternal-fetal testing of postterm pregnancie s (greater than or equal to 41 weeks' gestation) occurred at our institutio n. Maternal assessment included vital signs and urinalysis. The presence an d degree of maternal ketonuria was correlated against abnormal results of f etal heart rate tests, nonstress tests, amniotic fluid index measurements, and biophysical profile scores performed on the same day. RESULTS: There were 3601 encounters suitable for inclusion in the study. Cl inically detectable ketonuria occurred in 10.9% of the patients studied. Pa tients with clinically detectable ketonuria were at increased risk relative to patients without ketonuria for abnormal outcomes during postterm testin g, including the presence of oligohydramnios (24% vs 9.3%; P < .0001), nonr eactive nonstress tests (6.2% vs 2.15%; P < .0001), and fetal heart rate de celerations (14% vs 9.2%; P = .0039). CONCLUSION: Maternal ketonuria among patients with postterm pregnancy was a ssociated with a >2-fold increase in the occurrence of oligohydramnios, a 3 -fold increase in nonreactive nonstress tests, and a significant increase i n fetal heart rate decelerations. Further studies are required to evaluate the potential benefits of treating ketonuria before fetal testing.