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Published on: June 29, 2013
Third-Trimester Conditional Reference Values for Longitudinal Fetal Growth Assessment
Tri Rahmat Basuki1, Stefania Triunfo, Javier Caradeux
1Fetal i+D Fetal Medicine Research Center, BCNatal - Barcelona Center for Maternal-Fetal and Neonatal Medicine (Hospital Clínic and Hospital Sant Joan de Déu), IDIBAPS, University of Barcelona, and Centre for Biomedical Research on Rare Diseases (CIBER-ER), Barcelona, Spain.
Objectives:
The aim of this study was to derive longitudinal reference values of fetal growth (estimated fetal weight [EFW] and abdominal circumference [AC]) during the third trimester and to develop coefficients for conditional growth assessment.
Patients And Methods:
A prospective cohort study was conducted involving consecutive singleton pregnancies in a low-risk population for a routine third-trimester scan at 30+0-34+6 weeks and follow-up at 37+0-38+6 weeks for an additional ultrasound. Statistical analysis was based on multilevel modeling using MLwiN software. Unconditional centiles were calculated from z-values at each gestational age, and conditional centiles were calculated from z-values at a given measurement (30-34 weeks) and the expected measurement (37-38 weeks).
Results:
At 30-34 weeks, 8 and 9.3% of the fetuses had an unconditional EFW below the 10th and above the 90th centile, respectively. At 37-38 weeks, these figures were 10.3 and 9.3%, respectively. Regarding the unconditional AC, at the first scan, 8.9 and 9.6% had values below the 10th and above the 90th centile, while at the second scan 10.5 and 10.5% had values below the 10th and above the 90th centile, respectively. The proportion with a conditional EFW below the 10th and above the 90th centile was 10.2 and 9.4% at the second scan, respectively. For conditional AC, these figures were 10.7 and 10.3%, respectively.
Conclusion:
We have produced reference centiles for EFW and AC growth during the third trimester as a useful tool for quantifying growth.
