A single abnormal MOM value should be taken seriously and further investigations should be done. There are two types of MOM values: alpha-fetoprotein and human chorionic gonadotropin. In the case of an abnormal alpha-fetoprotein MOM value, such as a lower-than-normal value, the condition indicates that the fetus is at risk for congenital malformations. If the human chorionic gonadotropin MOM value is abnormal, for example, higher than the normal range, this condition should also be considered as a risk of having a fetus with Down syndrome. The MOM value is usually the result of a Down’s syndrome screening test, which uses a combination of alpha-fetoprotein, human chorionic gonadotropin, and free estriol to determine whether the fetus has a congenital disorder such as Down’s syndrome, trisomy 18, or neural tube defects. Abnormal single MOM value is needed for further examination. If the review is within the normal reference value, amniocentesis can be avoided for the time being; if the review result is still abnormal, further amniocentesis is needed for diagnosis.