Background: Blood urea nitrogen (BUN) and creatinine (SCr) are associated with gestational diabetes mellitus (GDM). However, there were limited data in the literature on the influence of BUN and SCr on maternal and fetal outcomes of pregnancy. We aimed to examine the association of BUN and SCr levels during gestation with the risk of selected adverse pregnancy outcomes.Methods: This retrospective cohort study included 1606 singleton mothers aged 22-44 years. Both BUN and SCr levels were collected and measured during the second (16-18th week), third (28-30th week) trimesters of gestation respectively and followed up pregnancy outcomes. Statistical analysis was used multivariate logistic regression. Results: In the multivariate adjusted logistic regression model, the highest level of SCr in the second trimester increased the risk of PROM by 45% (95% CI, 1.01-2.09). In the third trimester of gestation, compared with those in the lowest quartile, BUN levels in the highest quartile decreased the risk of macrosomia and LGA by 60%(95% CI, 0.20-0.78), 66%(95% CI, 0.21,0.55) , respectively, and increased the risk of SGA by 137%(1.06, 5.31), 186%(1.29,6.34) in the third and fourth quartiles, respectively. The adjusted OR (95%CI) for macrosomia in the fourth quartile was 0.46 (0.24, 0.87), for SGA in the third quartiles was 2.36 (1.10, 5.10), and for LGA in the fourth quartile was 0.61 (0.41,0.91) compared with those in the first quartile of SCr levels. The elevated changes of BUN (> 0.64mmol/L) was the risk factor of SGA (OR: 2.11, 95%CI: 1.03,4.32).Conclusion: Higher BUN and SCr levels during the 28-30th week of gestation even those towards the upper limit of the normal range can act as a warning sign of the impending SGA. Elevated changes of BUN and SCr during pregnancy also associated with the lower birth weight.
