Table 1.

Summary of gestational age modeling approaches.

Group	Ontario, Canada	Iowa, USA	California, USA
Newborn Screening Program	Newborn Screening Ontario	Iowa Newborn Screening Program	California Newborn Screening program
Sample size used for model development and testing	249,700	230,013	729,503
Years captured	2009–2011	2004–2009	2005–2011
Standard used for gestational age comparison	LMP, fetal ultrasound or combination	LMP or fetal ultrasound	Fetal ultrasound, 11–20 weeks’ gestation
Number of metabolite terms used in final model	44	37	35
Clinical factors included in final model	Birth weight, sex	Final model included metabolite terms only. Performance of final model evaluated with each addition of: month/year of collection, age (hour) at collection, birth weight, sex	Birth weight, age (hour) at collection
Infants correctly classified within 1 week of true gestational age	66.8%	78%	78.3%*
Infants correctly classified within 2 weeks of true gestational age (%)	94.9%	95%	91.7%*

*model performance amongst preterm infants only, <37 weeks’ gestation where 99.5% of the infants were correctly classified as ‘term’ or ‘preterm’. LMP: Last Menstrual Period