在15周到18周之间有两个极好的检查可以选择来甄别染色体异常和神经管缺损症状，比如：唐氏综合症和脊柱裂。
There are two test options available between the 15th and 18th weeks to screen for chromosomal abnormalities and neural tube defects such as Down's syndrome and spina bifida.
患有唐氏综合症的人经常会有其他症状。
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