We appreciate the article by Tangren et al.1 and read it with great interest. The authors conducted a large, retrospective cohort study of 462,053 women with 565,907 pregnancies. The study found that low eGFR with concurrent proteinuria was associated with increased risk of adverse pregnancy outcomes. We congratulate the authors for the successful article and would like to make some comments.
First, previous studies have shown that CKD was associated with a higher risk of adverse pregnancy outcomes,2 and this study yielded a similar conclusion with various categories of eGFR and proteinuria. Of note, in clinical practice, many women often consult about the effect of renal function on pregnancy outcomes, especially in women with abnormally elevated serum creatinine (SCr) or eGFR <60 ml/min per 1.73 m2. They are mainly concerned about two issues. First, what effect a low eGFR will have on pregnancy outcomes? Second, whether pregnancy will accelerate the progression of kidney disease? However, this article only focused on the first question. Much of the previous literature3 about the second issue indicated that women with preexisting kidney disease risked more rapid progression to kidney failure or eGFR decline if they became pregnant. However, these studies were single-center or case reports with less number of participants. Thus, it is still necessary to clarify the association of pregnancy with the progression of CKD using a large cohort.
Second, although the outcome of AKI was rare in women with advanced CKD in this study, we still cannot ignore it. We should pay attention not only to preconception kidney function but also to changes in SCr levels during pregnancy. Glomerular hyperfiltration is a typical physiological adaptation to early pregnancy, and consequently, SCr concentrations decline in the first trimester, plateau in the second, and increase in the third trimester.4 Although creatinine-based equations used to estimate GFR accurately reflect the physiological changes in renal function during pregnancy, Kidney Disease Improving Global Outcomes criteria for AKI may miss some cases. Creatinine values in the third trimester that are modestly elevated from the baseline may reflect a substantial fall in GFR from the normal expected level of hyperfiltration. It is possible, but unknown, whether cystatin-C–based eGFR estimation will be useful in this setting. In addition, to date, it is still unknown whether AKI onset during pregnancy has a poor prognosis for the newborn.
In summary, we constantly obtain new evidence regarding the relationship between renal function and maternal/fetal outcomes, but we still face challenges.
Footnotes
Published online ahead of print. Publication date available at www.jasn.org.
See related article, “Authors’ Reply: Renal Function and the Adverse Maternal and Fetal Outcomes: New Evidence,” on page 1472 and original article, “Pre-Pregnancy eGFR and the Risk of Adverse Maternal and Fetal Outcomes: A Population-Based Study,” in Vol. 34, Iss. 4, on pages 656–667.
Disclosures
The authors have nothing to disclose. The Medical Ethics Committee of Guangdong Second Provincial General Hospital approved the study.
Funding
None.
Author Contributions
Conceptualization: Shiyuan Wei.
Project administration: Shiyuan Wei.
Supervision: Shiyuan Wei.
Writing – original draft: Shiyuan Wei.
Writing – review & editing: Zhenbo Ouyang, Liangzhi Wu.
References
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