Interpretation
Previous studies have shown cognitive decline months to years after a pregnancy complicated by pre-eclampsia.17-19 To our knowledge no studies have assessed cognitive function before delivery or assessed cognitive function objectively at time of disease. Our findings would imply that the cognitive decline observed postpartum in earlier studies does not exist before onset of disease and is reported only in pre-eclampsia with severe features after diagnosis. To support this theory, subjective cognitive decline seems to increase by severity of disease and in particular by number of fits in women with previous eclampsia, arguing for a dose-response mechanism.17 It would be important to follow up our findings with long term studies to assess if these acute findings found in our population are reversible and if they correlate with longer term impaired cognitive function months to years after the pregnancy. In addition, cognitive function needs to be studied in combination with cerebral imaging and more in-depth cognitive function assessment on short- and long-term.
The CFQ was developed to assess cognitive function using daily life activities and does not have a cut off for normal function. It is recommended to perform the CFQ in generally comparable groups and to compare scores on a group level. The CFQ is a retrospective instrument subject to the limitations of human memory. It has been reported to change after severe physical stress or trauma like a brain injury and might be affected by a severe disease such as pre-eclampsia and in addition, CFQ has been designed to be used in a high income setting.20 Yet, the CFQ is the most commonly used assessment for cognitive function after pre-eclampsia.19, 21, 22 In our study, many of the participants live in poverty and some of the items on the CFQ were not applicable. Examples include questions such as ‘Do you find yourself forgetting why you went from one part of/room in the house to the other’. Many of the women in our study live in a single room where they sleep and eat. ‘Do you find yourself forgetting what you came to the shop to buy?’ was also problematic as many answered that they always only buy white bread. Although this may have influenced the outcomes, the groups were comparable.
The MoCA test was also developed in a high income setting and a score of 26 points is the cut off for normal cognitive function.16 In our population, even though women with normotensive pregnancies and non-complicated pre-eclampsia scored higher, the mean scores in these groups were 25.8 and 26.1 points respectively which correlates to borderline normal cognitive function. In a cross sectional study examining 370 healthy 18 year old South African males and females, the optimal cut off for sensitivity and specificity to detect cognitive impairment through the MoCA test was 24 points.23 Thus, women with normotensive pregnancies and non-complicated pre-eclampsia in our study scored above the suggested cut off for cognitive impairment whereas women with severe pre-eclampsia and in particular eclampsia scored below the limit of normal cognitive function. Many of the women with pre-eclampsia with severe features, including all those with eclampsia, were treated with magnesium sulphate for neuroprotection during their hospital stay. Magnesium sulphate has been shown to improve cognitive function in pregnant women.24 However, magnesium sulphate was not administered at the time of testing and scores were generally lower in women that had undergone treatment with magnesium sulphate (predominately women with eclampsia).