Abstract: Objective To explore the correlation between low development quotient of children and first-trimester serum level of free fatty acids in the mothers,and to provide a basis for supplementing food rich in fatty acid in early pregnancy.Methods The Bayley Scales of Infant Development of China Revision (BSID-CR) was used to evaluate the development of the infants(n=811).Children with mental development index(MDI)<P₅ (1.64 standard deviation below the mean) were classified as the low development quotient group (cases,n=43).One case was paired with three children with normal intelligence matched for maternal age,education,and family income.We used gas chromatography-mass spectrometry(GC-MS)to determine first-trimester serum level of free fatty acids.Results There were significant differences in the levels of polyunsaturated fatty acis(PUFA),ω-3PUFA,ω-6PUFA,docosapentaenoic acid(DPA),docosahexaenoic acid(DHA),eicosapentaenoic acid(EPA),EPA+DHA,DHA+anachidonic acid(AA) between the cases and the controls (P<0.05 for all).High level of EPA served as a protective factor of child low development quotient (odds ratio=0.37,95% confidence interval: 0.17-0.79).Correlation analysis demonstrated that there were relationships between EPA and DPA(r=0.608),DHA(r=0.659),AA(r=0.605),and DHA+AA(r=0.676).The level of EPA in maternal serum showed a downward trend with the reduced frequency of fish and other seafood intake (F=3.410,P=0.019).Conclusion The study suggests that there is an association of child's low development quotient with the lack of PUFA supplement of the pregnancy woman.Pregnant women should supplement PUFA to ensure normal mental development of the infant.