it happens to be that I studied this subject some years ago, spacifically, moon and fertility, scuse my english, I wouldnt know if i am spelling correctly
any way, I found out that the moon only relates to fertility cicles, I didnt studied the relation between male and female births. I used statistics to prove that the moon had influence in being or not fertile, but it came out that it had little influence compared to Jupiter!! So the results did surprised me and my colleges also.
About your question, in my research I did find out that the longer a sperm has to wait for the ovule egg, the higher the chances of conceiving a girl, and the longer the ovule egg has to wait for a sperm, he higher the chances of conceiving a boy. but you better check for yourself with a proper Dr.
For what I remember, this was just a theory yet to be proven...