Reference interval for 24-hour urinary protein excretion in uncomplicated women with twin pregnancies - Original Research

Q: What is the main purpose of the study on 24-h UTP in twin pregnancies?

To establish trimester-specific reference intervals for 24-hour urinary total protein excretion in uncomplicated women with twin pregnancies and to compare them with singleton pregnancies.

Q: How were reference intervals determined in the study?

Participants collected standardized 24-hour urine samples, data were extracted from electronic medical records, and a nonparametric percentile method was used to define reference intervals by trimester.

Q: What key finding describes changes in 24-h UTP across pregnancy in twins?

24-h UTP increased significantly throughout pregnancy in twin gestations, and the upper limit of normal excretion was 415.7 mg in late pregnancy.

Sep 29, 2026

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Study focuses on establishing reference intervals for 24-hour urinary total protein (24-h UTP) excretion in uncomplicated twin pregnancies and comparing values with singleton pregnancies. A large cohort of 12,633 participants provided standardized 24-h urine samples, with results stratified by trimester and analyzed using a nonparametric percentile approach. Findings show a significant, trimester-wide increase in 24-h UTP in twins, with the upper normal limit reaching 415.7 mg in late pregnancy.

LanguageEnglish

CategoryHealthcare

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Pages9

Reading Time23 min

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Original Research AJOG Global Reports Reference interval for 24-hour urinary protein excretion in uncomplicated women with twin pregnancies Yuguo Deng, MD; Lanyun Liu, BS; Danxiu Lu, BS; Qiulu Wu, MD; Ying Li, PhD; Jinying Yang, PhD | | BACKGROUND: The study of 24-hour urinary total protein (24-h UTP) excretion is an essential parameter for the assessment of renal function and early detection of pregnancy complications. However, data on reference interval for 24-h UTP in women with twin pregnancies are scarce.
OBJECTIVE: We aimed to establish the reference interval for 24-h UTP excretion in women with twin pregnancies and compare it with that in women with singletons.
STUDY DESIGN: A total of 12,633 participants with singletons or twin pregnancies were recruited. They were instructed to collect standard 24-hour urinary samples. Information was extracted from the electronic medical record. The nonparametric percentile method was used to determine reference interval for 24-h UTP excretion during different trimesters in women (excluding, among others, those with preexisting renal disease, gestational or chronic hypertension, pre-eclampsia, and pregestational diabetes mellitus) .
RESULTS: In twin pregnancies, the 24-h UTP levels expressed as medians and percentiles (5th, 95th) for each trimester were as follows: 74 .2 (32 .7, 195 .5) mg, 104 .5 (41 .9, 213 . 1) mg, and 152 .6 (46 . 1, 415 .7) mg in the ﬁrst, second, and third trimesters, respectively. A signiﬁcant increase in 24-h UTP excretion was observed throughout pregnancy (all P< .001) . Furthermore, the median (25th, 75th) of 24-h UTP values in the singleton group and twin groups were 70.2 (48.5, 98.3) vs 74.2 (47.3, 108.2) mg, 84.8 (58.5, 118.2) vs 104.5 (78.4, 135.6) mg, and 108.0 (73 .4, 149 .3) vs 152 .6 (90 .8, 192 .8) mg in the ﬁrst, second, and third trimesters, respectively. (Part of the data on singleton pregnancy has previously been published) . The 24-h UTP excretion in the twin group was signiﬁcantly higher than those in the singleton group in the second and third trimesters (both P< .001) .
CONCLUSION: Physiological proteinuria levels were approximately doubled in late pregnancy in women with twin pregnancies compared to early pregnancy, and the upper limit of normal 24-h UTP excretion is 415 .7 mg in late pregnancy. Moreover, the threshold for elevated proteinuriain twin pregnancies could be higher than in singletons from the second trimester onwards. Understanding these changes is essential for precise twin management and patient counseling.
Key words: reference interval, 24-hour urinary total protein excretion, uncomplicated, women with twin pregnancies | | | --- | --- | --- | Introduction Pregnancy is accompanied by remarkable physiological changes in the kidneys, with the glomerular ﬁltration rate (GFR) increases by 40% to 65%, and plasma ﬂow through the kidneys rises by 50% to 85% .1 Proteinuria is a nonspeciﬁc marker of renal dysfunction and a key criterion for distinguishing pre-eclampsia (PE) from gestationaland chronic hypertension. Proteinuriais characterized by a gestational agerelated increase in urinary protein excretion compared to prepregnancy levels. This increase is attributed to physiological glomerular hyperﬁltration and changes in permeability during pregnancy.2 Monitoring proteinuria is crucial for the early detection and management of PE, which is a leading cause of maternal mortality.3 Establishing baseline proteinuria levels during pregnancy is essential for distinguishing between gestational proteinuria and From the Department of Obstetrics, Longgang District Maternity & Child Healthcare Hospital of Shenzhen City, Shenzhen, Guangdong, China (Deng, Liu, Lu, Wu, and Yang); Longgang Maternity and Child Clinical Institute of Shantou University Medical College, Shenzhen, Guangdong, China (Deng, Liu, Lu, Wu, and Yang); Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdon

FAQs

What is the main purpose of the study on 24-h UTP in twin pregnancies?

To establish trimester-specific reference intervals for 24-hour urinary total protein excretion in uncomplicated women with twin pregnancies and to compare them with singleton pregnancies.

How were reference intervals determined in the study?

Participants collected standardized 24-hour urine samples, data were extracted from electronic medical records, and a nonparametric percentile method was used to define reference intervals by trimester.

What key finding describes changes in 24-h UTP across pregnancy in twins?

24-h UTP increased significantly throughout pregnancy in twin gestations, and the upper limit of normal excretion was 415.7 mg in late pregnancy.

Sep 29, 2026

Upload by Fans