Temporal trends, patterns, and predictors of preterm birth in California from 2007 to 2016, based on the obstetric estimate of gestational age

Table 3 Percentage of singleton births at 23–41 weeks of gestation based on obstetric estimates (OE) for the six categories of intrauterine growth stage for the 4,917,260 such singleton births in California from 2007 to 2016, with the percentage of LBW infants in parenthesis

Category	2007	2008	2009	2010	2011	2012	2013	2014	2015	2016
Preterm-SGA	0.4 (100)	0.4 (100)	0.4 (100)	0.5 (100)	0.4 (100)	0.4 (100)	0.4 (100)	0.4 (100)	0.4 (100)	0.5 (100)
Preterm-AGA	5.8 (47.9)	5.8 (47.4)	5.6 (48.8)	5.5 (49.5)	5.5 (49.9)	5.5 (49.6)	5.4 (50.7)	5.3 (49.9)	5.5 (50.6)	5.6 (49.9)
Preterm-LGA	1.2 (17.0)	1.1 (17.3)	1.0 (17.6)	1.0 (19.5)	0.9 (19.6)	0.9 (20.3)	0.9 (21.7)	0.9 (19.9)	0.9 (20.4)	0.9 (19.7)
Term-SGA	4.9 (29.4)	4.8 (29.0)	5.0 (28.7)	5.0 (29.0)	5.0 (28.2)	4.9 (28.2)	5.0 (28.2)	5.0 (27.7)	5.0 (28.0)	4.9 (27.9)
Term-AGA	81.1 (0.4)	81.2 (0.4)	81.6 (0.4)	81.8 (0.4)	82.0 (0.5)	82.0 (0.5)	82.2 (0.5)	82.3 (0.5)	82.3 (0.5)	82.0 (0.5)
Term-LGA	6.7 (0.0)	6.6 (0.0)	6.4 (0.0)	6.3 (0.0)	6.3 (0.0)	6.3 (0.0)	6.1 (0.0)	6.1 (0.0)	5.9 (0.0)	6.1 (0.0)
Preterm-SGA + Term-SGA	5.3 (35.2)	5.3 (34.7)	5.4 (34.3)	5.5 (34.8)	5.4 (34.0)	5.3 (34.1)	5.4 (33.9)	5.5 (33.4)	5.4 (33.9)	5.4 (33.9)

Preterm: < 37 weeks of gestation; Term: ≥37 weeks of gestation; SGA Small for gestational age, AGA Appropriate for gestational age, LGA Large for gestational age, LBW Low birth weight (< 2500 g)