Kidney dysfunction before pregnancy may increase risk for pre-term birth
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Women with elevated serum creatinine levels before pregnancy may have a greater risk for giving birth pre-term, according to a recent study.
The findings led Ziv Harel MD, MSc, of St. Michael’s Hospital in Toronto, and colleagues to suggest clinicians measure serum creatinine during pre-pregnancy risk assessments, especially since the measurements can be done with a “readily available and inexpensive blood test.”
“Prepregnancy kidney dysfunction may perturb the normal physiologic adaptations of pregnancy, predisposing a woman and her fetus to adversity, at least partly mediated by placental and endothelial dysfunction,” the researchers explained. “Complications such as preeclampsia and poor fetal growth may necessitate provider-initiated preterm birth. Preterm birth of any form before 37 weeks’ gestation occurs in 6% to 11% of viable pregnancies and is the leading cause of infant death.”
Arguing that previous studies investigating the link between kidney dysfunction and pre-term birth were primarily case series that lacked adequate “statistical power” and did not account for relevant confounders, Harel and colleagues assessed 55,946 pregnancies that occurred in Ontario between 2006 and 2016. All participants had a measurement of serum creatinine within 10 weeks preceding their estimated conception date with “abnormally” elevated levels defined as greater than the 95th percentile (> 77 mol/L). According to the researchers, this cutoff was derived from a sample of women without kidney disease who became pregnant shortly after the serum creatinine measurement was obtained.
Adjustments were made for maternal age, rural or urban residence, residential income, world region of origin (Asia, Caribbean/Africa, Hispanic America or other), diabetes, chronic hypertension and use of tobacco or illicit drugs within 4 years before conception.
Of total pregnancies, 7.1% occurred pre-term, or before 37 weeks’ gestation. The researchers found that the risk for pre-term birth was higher among women who had pre-pregnancy creatinine levels above the 95th percentile than among those with normal serum creatinine (9.1% vs. 7%; adjusted relative risk = 1.23).
Further, the associated risk for severe preterm birth, defined as before 32 weeks’ gestation, was doubled for women with elevated pre-pregnancy serum creatinine levels (2% vs. 0.93%; adjusted RR = 2.04).
The researchers also determined that, of all preterm births, 57% were initiated by the provider and 43% were spontaneous, with findings showing the adjusted RR was significant for provider-initiated pre-term birth but not for spontaneous pre-term birth.
Elaborating on this finding, Harel and colleagues wrote, “Elevated serum creatinine was notably associated with an increased risk for outcomes of a fetus severely small for gestational age and preeclampsia, which may be reasons for the increase in provider-initiated preterm birth but not spontaneous preterm birth.”
Based on these results, the researchers expressed concern that the American College of Obstetricians and Gynecologists does not make specific recommendations for women with kidney dysfunction who are planning a pregnancy.
“It may be appropriate in future guidelines to consider the importance of serum creatinine measurement before pregnancy or during the time of prenatal serum screening, especially given the test’s low cost and widespread availability,” they concluded. “Development of patient-specific clinical prediction models for preterm birth or preeclampsia should likely include a test for the added value of the serum creatinine concentration.”
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