What Causes Clubbing Of Toenails And Fingernails During Pregnancy?

hi, i am 33 years of age. i recently gave birth to my 4th child. During the 5th/6th month of pregnancy i noticed clubbing of toenails and fingernails. I understand clubbing could be a result of a chronic disease related to liver/kidney/heart/lung. Is there a chance this could only be an effect of pregnancy and not permanent/chronic disease?