Preeclampsia Prediction in Type 1 Diabetes and Diurnal Blood Pressure Methodology

The most recent Cochrane reviews on oral antihypertensive drugs in pregnancy conclude that no substantial benefits for the mother or fetus are demonstrated so far. Whether this applies for a high-risk and diabetic pregnancy is doubtful. The aim of this short review is an introduction to the field of ambulatory blood pressure measurements in pregnancy and in particular in women with type 1 diabetes. Diabetic pregnancy is complicated with a 50% risk of hypertension/preeclampsia. In the nonpregnant, diabetic women minute increases in blood pressure as well as in albuminuria are forerunners for incipient and overt nephropathy. Medication is essential and can conserve renal function, modifying the risk of renal insufficiency. During pregnancy, renal insufficiency in women with diabetes leads to termination of pregnancy. Therefore, detection of minute changes based on reliable measurements in this high-risk population is invaluable to protect the mother's kidney function and, if possible, prolong pregnancy for the benefit of the fetus. Estimates of risk by blood pressure evaluation in these women are influenced by pregnancy per se and diabetes vasculopathy. Several factors have to be considered as few monitors are validated for use in pregnancy and not many of the different methodologies have undergone thorough investigation. The use of absolute values of blood pressure have the advantage that fewer assumptions are necessary on how blood pressure behaves due to modes of evaluation and biological rhythm. Monitors should be chosen with care considering the clinical setting, timing, and population, which influences the outcome, thus, the monitors ought to be validated for the specific condition they are applied for. The strategy for the studies used for safe conclusions in this brief review was chosen with priority of the papers with the best, validated methodology on BP measurements, which is by no way guaranteed in numerous recent publications. Inherent characteristics of the measurements to be considered are reproducibility, consistency, precision, and trend over scale of measurement. Studies on these issues suggest that consistency and precision depend on which monitor is used. During pregnancy, the reproducibility and specificity depend on the timing and whether measurements are performed repeatedly. Over- and underestimations of blood pressure are typical for 24-h monitoring in high- as well as low risk pregnancies. Preeclampsia is associated with urinary albumin excretion rate, reduced night/day ratio, and elevated diurnal blood pressure from first trimester and onwards. However, due to blunting of the diurnal variation, the night/day rhythm provides no good prediction of preeclampsia. Diurnal measurement is a valuable estimate of blood pressure in terms of sensitivity, specificity, and predictive values.