INTERGROWTH-21st v. local South African growth standards (Theron-Thompson) for identification of small-for-gestational-age fetuses in stillbirths : a closer look at variation across pregnancy
CITATION: Lavin, T., et al. 2019. INTERGROWTH-21st v. local South African growth standards (Theron-Thompson) for identification of small-for-gestational-age fetuses in stillbirths : a closer look at variation across pregnancy. South African Medical Journal, 109(7):519-525, doi:10.7196/SAMJ.2019.v109i7.13485.
The original publication is available at http://www.samj.org.za
Background. Global growth standards for fetuses were recently developed (INTERGROWTH-21st). It has been advocated that professional bodies should adopt these global standards. Objectives. To compare the ability of INTERGROWTH-21st with local standards (Theron-Thompson) to identify small-for-gestational-age (SGA) fetuses in stillbirths in the South African (SA) setting. Methods. Stillbirths across SA were investigated (>500 g, 28 - 40 weeks) between October 2013 and December 2016 (N=14 776). The study applied the INTERGROWTH-21st standards to classify stillbirths as <10th centile (SGA) compared with Theron-Thompson growth charts, across pregnancy overall and at specific gestational ages. Results. The prevalence of SGA was estimated at 32.2% and 31.1% by INTERGROWTH-21st and Theron-Thompson, respectively. INTERGROWTH-21st captured 13.8% more stillbirths as SGA in the earlier gestations (28 - 30 weeks, p<0.001), but 4.0% (n=315) fewer between 33 and 38 weeks (p<0.001). Observed agreement and the Kappa coefficient were lower at earlier gestations and at 34 - 36 weeks. Conclusions. Our findings demonstrated differences in the proportion of stillbirths considered SGA at each gestational age between the INTERGROWTH-21st and the local SA standard, which have not been considered previously by other studies.
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