#5425 CHANGES IN SERUM CREATININE DURING AND AFTER PREGNANCY IN WOMEN WITH OR WITHOUT CHRONIC KIDNEY DISEASE: AN OBSERVATIONAL STUDY
Authors: Marxer Carole , Paik Julie , Zhuo Min , Desai Rishi , Hagberg Katrina Wilcox , Jick Susan , Meier Christoph , Spoendlin Julia 
Published: June 2023

Abstract

Background and Aims
In women with chronic kidney disease (CKD), kidneys may not sufficiently adapt to physiological changes during pregnancy, which may accelerate postpartum loss in renal function. We aimed to characterize pregnant women with or without renal impairment and to describe changes in renal filtration during and until one year after pregnancy.

Method
We performed a descriptive study using primary care data from the United Kingdom-based Clinical Practice Research Datalink (CRPD) GOLD and linked hospital data (2000–2019) in 14’401 pregnancies with ≥2 serum creatinine (SCr) measurements between the year before and after pregnancy. Pregnancies were categorized by means of the median estimated glomerular filtration rate (eGFR) during baseline (proteinuria is not reliably recorded). We captured risk factors for CKD and described changes in SCr levels over time as proxies for renal filtration.

Results
Of 14’401 pregnancies, 84% had a baseline eGFR [ml/min/1.73m2] of ≥90, 13% between 75–89, 13% between 60–74, and &lt;1% between 15–59. Pre-existing hypertension, diabetes, and/or overweight was prevalent in 66.0% of women with an eGFR &lt; 60 (versus 51.3-54.4% in eGFR ≥ 60). Preterm delivery was recorded in 30.2% of women with an eGFR &lt; 60 (versus 9.4–9.8% in eGFR ≥ 60). In women with a low-normal eGFR between 75–89, median baseline SCr levels (mg/dL [μmol/L]) were 0.92 [81.33] (interquartile range (IQR) = 0.88–0.96 [77.79–84.86]), which decreased by 0.25 [22.1] by week 14/15, remained stable until week 30/31, increased to 0.94 [84.0] (IQR = 0.83–0.99 [73.37–87.52]) until week 3/4 postpartum, and decreased back to baseline by one year postpartum. In women with a moderately low baseline eGFR between 60–74, median baseline SCr levels were 1.05 [92.82] (IQR = 1.01–1.10 [89.28–97.24]) and patterns during pregnancy followed those of women with low-normal eGFR (decreased by 0.28 [24.74] until week 18/19, plateau until week 38/39). However, SCr levels increased slower in trimester 3 and early postpartum and reached baseline levels at week 9/10 postpartum. Women with a baseline eGFR between 15–59 (median baseline SCr levels = 1.43 mg/dL [126.41 μmol/L], IQR = 1.26–1.72 mg/dL [111.38–152.05 μmol/L]) showed renal adaptation in trimester 1 and 2, but increased SCr levels of 1.71 [151.16] (IQR = 1.32-2.36 [116.69–208.62]) in trimester 3, but sample size was small.

Conclusion
Adaptations of renal filtration were not impaired during or after pregnancy in 1’932 pregnancies of women with a low-normal eGFR between 75–89. In women with a moderately low eGFR between 60–74, the pattern was similar, but potentially prolonged hyperfiltration in trimester 3 and early postpartum requires further investigation. The pattern of renal adaptation in eGFR between 15–59 was similar in trimester 1 and 2. Increased SCr levels in trimester 3 may indicate insufficient renal function but results have to be interpreted cautiously due to small sample size and potentially selective measurements.