How pregnancy influences renal function in nephropathic type 1 diabetic women depends on their pre-conceptional creatinine clearance.

Pregnancy in type 1 diabetic women with overt nephropathy can lead to a further deterioration in renal function but it is not clear at what level of pre-conceptional GFR the risk for worsening of renal function begins to increase. Therefore we investigated the influence of pregnancy on renal function in 12 women (14 pregnancies) with pre-conceptional macroproteinuria and near-normal creatinine clearance (range 37-93 ml/min/1.73m2). S-creatinine, creatinine clearance (CrCL), HbA1c and blood pressure (BP) were measured before conception, during each trimester (12th and 24th week of gestation and last week before delivery) and three and six months post-partum. In five diabetic women with six pregnancies (group A) there was a physiological increase in CrCl of 36% up until the 24th week of gestation; their pre-conceptional mean CrCl was 80 (range 70-93) ml/min/1.73m2. In seven women with eight pregnancies (group B) CrCl decreased by 16% during the first two trimesters; the mean CrCl before conception was 61 (37-73) ml/min/1.73m2. In the last week before delivery CrCl worsened transiently in three cases in group A and four in group B, due to pre-eclampsia. Three months post-partum the mean CrCl in group A was 78 (70-91) ml/min/1.73m2, approximately the same as before pregnancy. In group B the mean CrCl was 39 (22-68) ml/min/1.73m2 at this same time; this was 36% lower than the pre-conceptional clearance. Mean HbA1c in both groups were approximately the same, but mean BP tended to be higher during pregnancy in group B, especially in the week before delivery (p<0.05). We conclude that in a high percentage of nephropathic diabetic women with significantly low CrCl before conception, renal function worsens during and after pregnancy. Inadequate antihypertensive therapy may contribute to this.