Conclusion
If the new sex-specific standard indeed represents normal fetal growth better than the Hadlock sex-neutral method, our findings suggest that fewer diagnoses of SGA and more diagnoses of LGA may be necessary. Under this assumption, it is female fetuses who may suffer most from use of the sex-neutral standard, since they are more likely to be inappropriately labeled as SGA and less likely to be appropriately labeled as LGA. This is concerning because fetuses with estimated size <10th percentile for gestational age in the U.S. undergo an intensive regimen of surveillance and often undergo delivery before 39 weeks even without evidence of compromise.3 Simultaneously, failing to recognize LGA may be associated with additional maternal and neonatal morbidity.4 Thus, our development of a sex-specific fetal growth standard represents a meaningful opportunity to reduce the sex disparity in diagnosis of both SGA and LGA created by the use of a sex-neutral growth standard. Whether or not a sex-specific fetal growth standard is ultimately found to improve prediction of perinatal morbidity and mortality, the fact that it resolves both statistically and clinically significant sex disparities in SGA and LGA is reason enough to consider its use.
Acknowledgments:
Disclosure of interests: the authors report no conflict of interest.
Authors contributed to this work as follows: Conception and planning: N.R.B., A.A.A., W.G., B.M., H.S., U.M.R., G.S., S.P., R.M.S., A.S., J.M.B-W., S.H.; carrying out: W.G., B.M., H.S. U.M.R., G.S., S.P., R.M.S.; Analyzing: A.A.A., N.R.B.; writing up: N.R.B., A.A.A., S.H., W.G., B.M., A.S., J.M.B-W., H.S., U.M.R., G.S., S.P., R.M.S.
Ethical oversight: Each participating center obtained ethical approval from the respective institutional review board. This secondary analysis was designated as exempt from review as non-human subjects research by the University of Utah Institutional Review Board (IRB number IRB_00113635)
This work was funded by the Eunice Kennedy Shriver National Institute for Child Health and Human Development (award numbers U10 HD063020, U10 HD063037, U10 HD063041, U10 HD063046, U10 HD063047, U10 HD063048, U10 HD063053, U10 HD063072, 2K12 HD085816-07). The funding awards for the parent study followed peer review for scientific quality and priority. Beyond the scoring and funding decisions, the funding agency did not play a role in the conduct or reporting of the research.