Leafy green vegetables such as spinach are rich sources of folic acid. Low levels of folate can give rise to distorted sperm shapes such as ones with two heads or two tails. The sperm are also at an increased risk of chromosomal abnormalities. This means that firstly your sperm will find it difficult to reach an egg and even if it does reach an egg, it will not be able to fertilize it. Furthermore, even if these sperms are able to fertilize an egg, the chances of birth defects are quite high in such cases.