Maternal and fetal determinants influencing the occurrence of congenital abnormalities of the kidney and urinary tract: a nested case–control study

Background: The causes of congenital abnormalities of the kidney and urinary tract (CAKUT ) are still not fully understood, although several risk factors have been identified. This study focuses on exploring the maternal and fetal factors that may contribute to CAKUT in southern China. Methods: A nested case-control design was implemented in Hainan, China, during the period 2021–2025. We included 109 CAKUT cases and 545 non-CAKUT controls from the Hainan women and children’s medical centre. Maternal characteristics were obtained through a combination of telephone interviews and in-person surveys. Clinical data were confirmed from medical records. A comparison of maternal and fetal factors in offspring with CAKUT and those without the condition was conducted. Independent determinants of CAKUT were evaluated using multivariable logistic regression. Results: After controlling for confounding factors, advanced maternal age emerged as a significant predictor of CAKUT (aOR = 2.56, 95%CI, 1.32 - 4.95). Body mass index (BMI) before pregnancy (aOR=3.19, 95%CI, 1.54 - 6.63), gestational hypertension (aOR=3.44, 95%CI, 1.30 - 9.10), hypothyroidism (aOR=11.31, 95%CI, 1.97 - 64.84), multiple pregnancies (aOR=7.49, 95%CI, 1.05 - 53.65) , and gestational age (aOR=4.70, 95%CI, 1.80 - 12.27) were confirmed. Conclusions: Hydronephrosis represented the most frequently observed subtype of CAKUT. An increased risk of CAKUT was linked to advanced maternal age, low pre-pregnancy BMI, gestational hypertension, hypothyroidism, multiple gestations, and gestational age.