At the shiva for my infant son, someone said that the reason we say kaparat pesha in mussaf rosh chodesh, is that to atone for the sins that cause higher rates of stillbirth, miscarriages, and infant deaths in the winter of a leap year.
I have tried to find a source for this. The Levush (תרפ”ה) says that Shovavim Tat was established because of stillbirth and miscarriages in leap years. Olam Hatefilla by Rav E Munk on the words Kaparat Pesha quotes the Levush and adds in the name of "Acherim" about infant death.
I am looking for the WHO the "Acherim" are/is and also any additional sources on this topic.
(In the two months since my son went to Shomayim, i know of at least 9-10 infant deaths in the Greater Jerusalem Area alone!!)