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AJNR - American Journal of Neuroradiology

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American Journal of Neuroradiology 26:352-356, February 2005
© 2005 American Society of Neuroradiology

BRAIN

Phosphorus-31 Brain MR Spectroscopy in Women During and After Pregnancy Compared with Nonpregnant Control Subjects

Anita Holdcroft^a, Lisa Hall^a, Gavin Hamilton^b, Serena J. Counsell^b, Graeme M. Bydder^b and Jimmy D. Bell^b

^a Department of Anesthesia Imaging Sciences Department,MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, Hammersmith Hospital Campus, UK
^b Robert Steiner MR Unit , Imaging Sciences Department,MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, Hammersmith Hospital Campus, UK

Address reprint requests to Anita Holdcroft, Magill Department of Anaesthesia, Chelsea and Westminster Hospital, Fulham Road, London SW10 9 NH

BACKGROUND AND PURPOSE: A reversible decrease in brain size has been demonstrated during normal pregnancy that is maximal at term and returns to normal after many months. The purpose of this longitudinal study was to use phosphorus-31 MR spectroscopy to determine if metabolic changes explain this physiologic event.

METHODS: Pregnant women (n = 12) were examined at term and up to 6 months after delivery. Nonpregnant control subjects (n = 7) were imaged twice (a month apart) to exclude hormone effects. Brain ³¹P MR spectra were acquired at 1.5 T, and intracellular pH was calculated from the chemical shift between phosphocreatine and inorganic phosphate resonances. Statistical analysis was performed by using an analysis of variance.

RESULTS: We found no statistically significant differences in the relative levels of metabolite associated with cerebral bioenergetics and cell membrane metabolism between pregnant women and nonpregnant women. However, a significant increase in cerebral pH was observed in pregnant women at 6 weeks after delivery compared with control subjects (7.074 ± 0.063 vs 7.017 ± 0.041; P < .05). pH returned to normal by 6 months after delivery (7.014 ± 0.010).

CONCLUSION: Changes in brain size associated with pregnancy appear to be associated with an increase in intracellular pH after delivery. The observed alkalosis may reflect altered cellular metabolism. These persistent brain perturbations associated with pregnancy indicate that, when postpartum physiologic and pharmacologic changes are measured, long-term effects may be expected in central nervous system processing.