Table 3. Prevalence rates of BDs and crude ORs between 2005 and 2014 analyzed from the perspective of maternal characteristics.

	BDs(n)	Perinatal infants(n)(%)	Prevalence of BDs (per 10000 PIs)(95%CI)	OR(95%CI)
Region
urban	9319	444485(48.03)	209.66(208.46–210.86)	1.20(1.16–1.24)
rural	8436	480928(51.97)	175.41(174.31–176.51)	reference
Infant gender
male	10099	491527(53.11)	205.46(204.36–206.56)	1.19(1.15–1.23)
female	7513	433594(46.85)	173.27(172.17–174.37)	reference
Maternal age
<20	256	13535(1.46)	189.14(182.54–195.74)	reference
20~24	5319	282959(30.58)	187.98(186.58–189.38)
25~29	7358	394663(42.65)	186.44(187.64–185.24)
30~34	3253	165575(17.89)	196.47(194.57–198.37)
35~	1568	68681(7.42)	228.3(225.15–231.45)	1.24(1.17–1.30)