TABLE 1.

Count of NTD-affected pregnancies, neural tube defects (NTD) prevalence per 10,000 pregnancies and percent reduction by NTD type, folic acid (FA) use status, and geographical region in north and south of China, 1993–1996

	North							South
	No FA exposure			Complete FA exposure				No FA exposure			Complete FA exposure
	(N =73,813)			(N = 10,186)				(N = 433,595)			(N = 50,109)
NTD type	Count		Prevalence per 10,000 pregnancies	Count		Prevalence per 10,000 pregnancies	% prevalence reduction with FA use	Count		Prevalence per 10,000 pregnancies	Count		Prevalence per 10,000 pregnancies	% prevalence reduction with FA use
	N %			N %				N %			N %
All NTDs	273	100	37.0	7	100	6.9	81	341	100	7.9	29	100	5.8	26
Anencephaly	47	17	6.4	1	14	1.0	85	127	37	2.9	15	52	3.0	−2
Craniorachischisis	57	21	7.7	0	0	0.0	100	44	13	1.0	0	0	0.0	100
Iniencephaly	8	3	1.1	0	0	0.0	100	7	2	0.2	0	0	0.0	100
Encephalocele	29	11	3.9	2	29	2.0	50	58	17	1.3	8	28	1.6	−19
Total spina bifida	132	48	17.9	4	57	3.9	78	105	31	2.4	6	21	1.2	51
High lesion level	69	25	9.4	2	29	2.0	79	36	11	0.8	1	3	0.2	76
Low lesion level	59	22	8.0	1	14	1.0	88	67	20	1.5	5	17	1.0	35
Closed NTDs	65	24	8.8	3	43	2.9	67	88	26	2.0	10	34	2.0	2
Open NTDs	208	76	28.2	4	57	3.9	86	253	74	5.8	19	66	3.8	35

Note: The prevalence of neural tube defect (NTD) was calculated as the number of NTD-affected pregnancies divided by the total number of pregnancies with known birth outcomes, which could be confirmed as either having or not having an NTD. For spina bifida in the north, there were 4 and 1 NTD-affected pregnancies of unknown lesion level among folic acid nonusers and users, respectively. For spina bifida in the south, there were 2 NTD-affected pregnancies of unknown lesion level among folic acid nonusers. Women with incomplete exposures to folic acid were excluded from the table.