Fertility doctor Merel van den Berg of Jeroen Bosch Hospital said that people trying to conceive often rely on claims about how to improve their chances. She said there is no evidence that keeping the legs raised after sex leads to pregnancy more quickly, that no sexual position has been shown to improve the success rate, and that penis length does not matter. She added that having sex every day around ovulation is sufficient. Van den Berg, who helps couples and single people who have been trying to have children for at least a year, said she decided to write a book to provide information for making informed decisions. She also said people are not always aware of the effect that lifestyle can have on fertility.