Table 3. Ranking of 25 BD subtypes in total BDs over the period of policy changes (in 2013, 2015 and 2017).

Ranking	One-child policy period (2013)			Partial two-child policy period (2015)			Universal two-child policy period (2017)
	BD subtypes	N	Prevalence (per 10,000 births)	BD subtypes	N	Prevalence (per 10,000 births)	BD subtypes	N	Prevalence (per 10,000 births)
1	CHD	3,820	143.00	CHD	4,173	157.31	CHD	5,661	181.38
2	Polydactyly	508	19.02	Polydactyly	532	20.05	Polydactyly	631	20.22
3	Congenital malformation of urinary system	420	15.72	Congenital malformation of urinary system	429	16.17	Congenital malformation of urinary system	619	19.83
4	Cleft lip with cleft palate	256	9.58	Cleft lip with cleft palate	248	9.35	Cleft lip with cleft palate	405	12.98
5	NTDs	217	8.12	NTDs	189	7.12	Trisomy 21 syndrome	360	11.53
	Anencephaly	113	4.23	Anencephaly	99	3.73
	Spina bifida	71	2.66	Spina bifida	54	2.04
	Encephalocele	33	1.24	Encephalocele	36	1.36
6	Syndactyly	171	6.40	Other malformation of external ear	186	7.01	Other chromosomal defects	339	10.86
7	Congenital hydrocephalus	165	6.18	Trisomy 21 syndrome	174	6.56	Other malformation of external ear	309	9.90
8	Congenital talipes equinovarus	155	5.80	Syndactyly	166	6.26	Congenital talipes equinovarus	221	7.08
9	Other malformation of external ear	154	5.77	Congenital talipes equinovarus	164	6.18	NTDs	211	6.76
							Anencephaly	87	2.79
							Spina bifida	72	2.31
							Encephalocele	52	1.67
10	Trisomy 21 syndrome	145	5.43	Hypospadias	157	5.92	Hypospadias	211	6.76
11	Cleft lip without cleft palate	142	5.32	Cleft lip without cleft palate	150	5.65	Syndactyly	202	6.47
12	Hypospadias	122	4.57	Other chromosomal defects	135	5.09	Congenital hydrocephalus	147	4.71
13	Cleft palate without cleft lip	107	4.01	Congenital hydrocephalus	117	4.41	Cleft lip without cleft palate	140	4.49
14	Limb reduction defects	106	3.97	Cleft palate without cleft lip	112	4.22	Congenital atresia of rectum and anus	119	3.81
15	Congenital atresia of rectum and anus	82	3.07	Limb reduction defects	105	3.96	Cleft palate without cleft lip	117	3.75
16	Other chromosomal defects	80	2.99	Congenital microtia	91	3.43	Congenital microtia	116	3.72
17	Omphalocele	67	2.51	Congenital atresia of rectum and anus	83	3.13	Limb reduction defects	108	3.46
18	Congenital diaphragmatic hernia	64	2.40	Omphalocele	79	2.98	Omphalocele	86	2.76
19	Gastroschisis	54	2.02	Gastroschisis	47	1.77	Gastroschisis	63	2.02
20	Congenital microtia	48	1.80	Congenital diaphragmatic hernia	39	1.47	Congenital diaphragmatic hernia	51	1.63
21	Congenital esophageal atresia	34	1.27	Congenital esophageal atresia	22	0.83	Congenital esophageal atresia	39	1.25
22	Conjoined twins	13	0.49	Conjoined twins	6	0.23	Conjoined twins	22	0.70
23	Exstrophy of urinary bladder	0	0.00	Exstrophy of urinary bladder	3	0.11	Exstrophy of urinary bladder	2	0.06

Note: yellow indicates chromosomal defects, and light purple indicates NTDs.

Abbreviations: BD, birth defect; CHD, congenital heart defect; NTD, neural tube defect