The physical union between man and woman may go deeper than what we as mere mortals may understand. The study of women who carried Y chromosomes names many reasons why a woman could carry male chromosomes without having a male baby, but it is still an interesting study to contemplate. https://www.ncbi.nlm.nih.gov/pubmed/16084184. Ever since I read this study it has made me wonder if the Bible was being literal, as well as figurative, when it says we "become one flesh".