[The epidemiology of neural tube defects in high-prevalence and low-prevalence areas of China].
OBJECTIVE
To describe the epidemiology of neural tube defects (NTDs) in high- and low-prevalence areas of China.


METHODS
Birth defects surveillance data, collected from 1992 through 1994 was analyzed. These data were collected as part of the Sino-American cooperative project on NTDs prevention. We classified NTDs as anencephaly, encephalocele, high-level and low-level spina bifida (SB) according to location of the lesion (high vs low) and whether the defect was isolated or occurred in association with other birth defects. Rates were compared in the high-prevalence (North) region and the low-prevalence (South) region, after adjusted for classification, urban and rural, season and sex, and calculated the adjusted rate of NTDs.


RESULTS
Among seven hundred and eighty-four NTDs cases in 326 874 recorded births (include in livebirth, stillbirth and fetal death with a gestational age of at least 20 weeks), the overall NTDs prevalence in the North was 5.57/1,000 births, and in the South was 0.88/1 000. There were also significant differences in the prevalence of anencephaly, encephalocele, high-level and low-level SB between North (0.97, 0.49, 2.75 and 1.11/1,000 birth) and South (0.36, 0.15, 0.21 and 0.14/1,000 birth) (P < 0.01), with adjusted prevalences in the North 3 - 7 times higher than those in the South. There were significant difference between urban (2.04) and rural areas (6.57/1,000 birth) in the North (P < 0.01), urban (0.52) and rural areas (0.95/1,000 birth) in the South (P < 0.05). Adjusted prevalence rates in the rural were 3 - 4 times higher than those of urban in the North and 1.6 - 1.9 times higher than in the South; The seasonal rate of high-level SB increased between September and November in the North (3.44/1,000 birth), while the seasonal rate of anencephaly decreased between September and November (0.18/1,000 birth) in the South. However there were no seasonal changes in other classified NTDs both in the South and North.


CONCLUSIONS
The birth prevalence of NTDs in the North of China was the highest in the world. There were significant differences between the North and the South, urban and rural. There was seasonal change in high-level SB in the North, which was in accordance to the phenotype of NTDs. It was suggested that there might exist etiological heterogeneity among anecephalus, low- and high-level SB.
Pei
Li-jun
LJ
Institute of Reproductive and Child Health, Peking University, Beijing 100083, China.
Li
Zhu
Z
Li
Song
S
Hong
Shi-xin
SX
Ye
Rong-wei
RW
Chen
Xin
X
Zheng
Jun-chi
JC
Wang
Tai-mei
TM
Zhao
Xiu-qin
XQ
Xiao
Lan
L
Wang
Li-na
LN
Zhang
Bo-lan
BL
Liu
Zhi-xin
ZX
Zhou
Yong-lan
YL
Jiang
Mei-fang
MF
Sun
Xia-mei
XM
Chen
Hai-lan
HL
Li
Min
M
Yang
Xiao-ling
XL
Shen
Quan-zhen
QZ
Shao
Pei-yun
PY
Xie
Lian-yun
LY
D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D009436:Neural Tube Defects / Q000453:epidemiology*; D012621:Seasons