Table 2. Socio-demographic data of study population.

Maternal age (year)	Number (%)	Maternal ethnicity (Taiwanese, %)	Residency (urban, %)
≤14	657 (0.03)	99.7	43.3
15	1898 (0.09)	99.2	34.6
16	4792 (0.23)	99.5	31.8
17	8927 (0.42)	99.3	29.7
18	15725 (0.74)	90.6	29.5
19	31892 (1.50)	76.5	30.3
20	46186 (2.17)	71.4	31.4
21	61888 (2.91)	70.2	31.6
22	76592 (3.61)	72.0	32.8
23	92300 (4.35)	75.7	34.2
24	107968 (5.08)	79.3	35.7
25	124073 (5.84)	82.7	37.2
26	141767 (6.68)	86.1	39.1
27	160788 (7.57)	88.9	41.5
28	173117 (8.15)	90.9	44.5
29	167574 (7.89)	92.1	47.1
30	164091 (7.73)	93.1	49.3
31	153504 (7.23)	93.7	51.8
32	136702 (6.44)	94.0	53.9
33	113629 (5.35)	94.2	55.3
34	91988 (4.33)	94.4	56.6
35	72484 (3.41)	94.3	57.3
36	55301 (2.60)	94.5	58.0
37	40545 (1.91)	94.7	58.7
38	28781 (1.36)	94.9	58.0
39	19940 (0.94)	94.7	58.9
40	13316 (0.63)	94.1	59.4
41	8096 (0.38)	94.4	59.6
42	4478 (0.21)	94.2	57.5
43	2470 (0.12)	94.7	57.4
≥44	2282 (0.11)	92.5	58.7