International Standards for Symphysis-Fundal Height Based on Serial Measurements from the Fetal Growth Longitudinal Study of the INTERGROWTH-21st Project: Prospective Cohort Study in Eight Countries

Fetal growth assessment is important to identify fetuses with abnormal fetal growth that are at increased risk of perinatal morbidity and mortality. Serial measurement of symphysis-fundal height (SFH) is the recommended, inexpensive, and first-level screening tool in both low- and high-risk pregnancies. However, SFH measurements show a wide range of sensitivities for detecting small for gestational age (SGA) owing to the different measurement methods, charts, and thresholds used to perform an ultrasound scan and the use of uncorroborated menstrual dates that can cause errors in dating and can lead to overestimating the length of gestation. A prospective longitudinal observational study, the Fetal Growth Longitudinal Study, one of the main components of the INTERGROWTH-21st Project, was conducted on healthy, well-nourished women to develop international SFH standards to improve antenatal care. Of the 13,108 women screened in the first trimester, 4607 met study criteria, and of these, 4321 (93.8%) delivered live singletons without congenital malformations or complications. The median number of SFH measurements in all women was 5.0 (range, 1–7); 3976 (92.0%) women had 4 or more measurements. Analysis of the duplicate SFH measurements obtained from all women showed that the 95% limits of agreement were approximately 1.5 cm. The international standards developed through this study overcome many of the methodological limitations of SFH measurement by reducing the wide range in sensitivity for the detection of SGA and should reduce the risk of failing to diagnose restricted and excessive fetal growth and help in comparisons across populations. The new international SFH standards in combination with standardized measurement methodology are recommended to improve clinical practice.