Isolated Proteinuria in Uncomplicated Twin Pregnancies vs. Singleton Pregnancies; Measured by Spot Protein-Creatinine...

Proteinuria is used for prediction of pre-eclampsia; however, the cutoff values are suggested for singleton pregnancies and might not be appropriate for twin pregnancies. In this study, we examined whether the urine spot protein-creatinine ratio (SPCR) is higher in twin than singleton pregnancies and what factors are associated with this difference.

In this prospective longitudinal study with repeated measures, pregnant mothers (aged 15-45 years) who referred to Mahdiye Hospital, Tehran, Iran, from April 2021 to November 2022 for routine prenatal care at least from the 15th gestational week were included in the study. Maternal age, body mass index, and gravidity were recorded. For measurement of SPCR, spot urine samples were collected from each participant at three predefined time points during pregnancy. Pregnancies complicated with (pre)gestational diabetes or pre-eclampsia, urinary tract infection, or other renal diseases were excluded from the study. The within-subject effects of variables on the groups were evaluated using repeated-measures ANOVA. A p value < 0.05 was considered statistically significant.

There were 89 mothers in the singleton group and 70 in the twin group. The mean age between the groups was not significantly different, but BMI and the distribution of gravidity differed between them. Higher median urine SPCR values were found in twin pregnancies in the mid-second and third trimesters (p = 0.005 and 0.022, respectively), with a significant trimester-by-group interaction effect in the overweight (p = 0.008) and obese subgroups (p = 0.004), as well as in women with Gravidity 1 (p = 0.012) and Gravidity ≥ 3 (p = 0.018).

Twin pregnancies have higher urine SPCR values than singletons; these findings suggest that current cutoff values may need re-evaluation in future studies to improve the prediction of pre-eclampsia in multifetal gestations.