Objective To analyze the effects of pregnant age and parity on the prevalence of fetal malformation from the perspective of birth defects. Methods 4500 birth records in our hospital between January 2012 and October 2013 in Department of Obstetrics and Gynecology were retrospectively analyzed. According to the national birth defect monitoring program, the prevalence rate of fetal malformation and the types of diseases were statistically analyzed. Women's age, parity, residence, history of disease, exposure of relevant harmful substances and premarital examination etc. were also statistically analyzed. The relationship between the above situations and the prevalence rate of fetal malformation was analyzed. Results Among 4500 women, there were 3712 cases who were 25 to 30 years old, accounting for 82.49%, 7 cases＜ 19 years old, accounting for 0.16%. Among 4500 women, 1765 cases had 1 child, accounting for 39.22%, and 465 cases had more than 4 children, accounting for 10.33%. There were 572 cases (12.71%) with fetal malformation, and the most were stillbirth (163 cases). The prevalence rate of fetal malformation in women＜ 19 years old was the highest ［71.43% (5/7)］, followed by 36 ~ 45 years old ［41.07% (35/56)］. The prevalence rate of women who were 25 to 30 years old was the lowest ［8.70% (323/3712)］. The prevalence rate of fetal malformation in women who had ≥ 4 parity was the highest ［17.20% (80/465)］. The differences in prevalence rate of fetal malformation between different residences (urban and rural), early pregnancy diseases (fever and non fever), exposure of harmful substances (radiation, exposure to noise and non radiation, normal environmental exposure), premarital and prenatal examination (or not) were significant (P＜0.05). Conclusion The prevalence rate of fetal malformation in women who are too young or too old is high. However, the effects of parity on the prevalence rate are relatively complex. Affecting by age effects, since most pregnant women are 25 to 30 years old, the two-child policy has little effect on the quality of population. In addition, the prevalence of fetal malformation is also related to prenatal examination, pregnancy diseases, environmental factors and so on.