Background: Among the environmental factors, diet has received much attention because of growing bulk of data that discloses significant and substantial role for dietary elements, particularly, micronutrient in fertility pathophysiology. One of the major dietary elements that have been recently under focus is dietary folate. A number of vital cellular events, such as transfer RNA, synthesis of DNA, methionine and cysteine, require folate as an essential molecular participant. A number of previous studies have documented that folate supplementation can improve fertility outcome; whereas, other studies have denied such an association between folate supplementation and fertility outcomes.
Aim of the study: to study a possible correlation between plasma and follicular fluid folate levels and the pregnancy rate in women enrolled in ICSI cycles.
Patients and methods: The present study was done on 65 infertile couples who were chosen from those attended the High Institute of Infertility Diagnosis and Assisted Reproductive Technologies who were subjected to an intracytoplasmic sperm injection (ICSI) cycles. Their ages ranged from 18 to 42 years. Both primary and secondary types of infertility were involved, with heterogeneous causes. From each woman, venous blood sample and follicular fluid sample was obtained for folate concentration determination using ELISA technique. 
Results: The biochemical pregnancy rate was 32.3 %. There was significant association between plasma folate level and positive pregnancy outcome (P < 0.05), when comparing the pregnancy rate of deficient group, lower normal group and high group with that of normal group. The highest pregnancy rate was observed in women with normal plasma folate and it equals 56.7 %, therefore it was considered a reference group for purpose of comparison. Pregnancy rate of deficient folate group was significantly lower than that of normal folate group, 11.1 % versus 56.7 % (P = 0.043). In addition, pregnancy rate of lower normal folate group was significantly lower than that of normal folate group, 10.0 % versus 56.7 % (P = 0.028). Moreover, pregnancy rate of high folate group was significantly lower than that of normal group, 12.2 % versus 56.7 % (P = 0.004). 
Conclusion: Both high and low plasma folate are associated with low pregnancy rate; therefore, it should be recommended that serum folate should be monitored when prescribing folate to infertile women and that it should be discontinued once its level reaches the maximum normal plasma range.

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