Change in brain size during and after pregnancy: study in healthy women and women with preeclampsia

Abstract

Background and purpose: Qualitative decreases in maternal brain size have been observed late in pregnancy. The aim of this study was to quantitatively evaluate changes to the maternal brain during and after healthy pregnancy and to compare these changes with those observed in cases of preeclampsia.

Methods: Three-dimensional T1-weighted MR volume images were obtained in nine healthy participants before and after delivery. Additional images were obtained in some of these participants before pregnancy, during pregnancy, and within 52 weeks after delivery. Five women with preeclampsia were examined before delivery and 6 weeks after delivery. Three of these patients were examined within 52 weeks after delivery. Images were registered, and both brain and ventricular volumes were calculated by using a semiautomated computer program.

Results: Both the healthy and preeclamptic groups had a reduction in brain size during pregnancy that was maximal at term and that reversed by 6 months after delivery. The ventricular size showed a corresponding increase in size during pregnancy and a decrease in size after delivery. In the preeclamptic patients, brain size was significantly smaller (P =.05) than in healthy participants, both before and after delivery.

Conclusion: The brain decreases in size during pregnancy and increases in size after delivery. The changes follow a consistent time course in each woman. The mechanism and physiologic importance of these findings are speculative at the present time.

Fig 1.

Images illustrate the contour and thresholding technique. A, Parasagittal 3D T1-weighted MR image of the brain with the brain contour. B, Transverse 3D T1-weighted MR image of the brain showing the initial ventricular contour. C, Binary image of the corresponding sections of the brain. D, Final binary image of the ventricles.

Fig 2.

Registered and subtraction images. A, Registered T1-weighted MR image obtained before conception. B, Registered T1-weighted MR image obtained at term. Slight ventricular enlargement can be seen, compared with the image in A. C, Subtraction image formed from the term image minus the preconception image. Ventricular enlargement is apparent as a dark line (small arrows). Decrease in the size of the brain is apparent at the external surface as dark lines (large arrow). D, Subtraction image formed from the image obtained at 24 weeks minus the term image. An increase in the size of the ventricles between term and 24 weeks produces a white line (small arrows), and an increase in the size of the brain produces a white line at the external surface (large arrow). E, Subtraction image formed from the image obtained at 24 weeks minus the preconception image. This largely featureless image is consistent with the brain and ventricles returning to their original preconception size at 24 weeks after delivery.

Fig 3.

Healthy group. A, Percentage changes in brain size before, during, and after pregnancy. The brain decreases in size until delivery and then increases in size again after delivery. B, Percentage changes in ventricular size before, during, and after pregnancy. Ventricles increase in size until delivery and decrease in size after delivery.

Fig 4.

Preeclamptic group. A, Percentage changes in brain size before and after delivery. Brain increases in size after delivery. Exception is the last image of one patient who was treated with diuretics. B, Percentage changes in ventricular size before and after delivery. Ventricles decrease in size after delivery.