Some invent a headache while others claim they are too tired.
But scientists believe there may be a medical reason why women give their husbands excuses for not wanting to make love.
They have discovered that the brains of females with a low libido behave completely differently to those with healthy sex drives.
Those with a low libido do not have the same rush of blood to certain brain cells during moments of passion, which could explain why they don’t enjoy it.
The US scientists compared the brains of 19 women diagnosed with a form of low libido known as hypoactive sexual desire disorder with the brains of seven women with a normal sex drive.