(Yes, this series has mpreg, at least potentially.)
2008 — Tan Bee Kee, "Rewriting Gender and Sexuality in English-Language Yaoi Fanfiction", in Boys' Love Manga: Essays on the Sexual Ambiguity and Cross-Cultural Fandom of the Genre (eds. Antonia Levi, Mark McHarry & Dru Pagliassotti), McFarland & Company (2008), →ISBN, page 140:
One sub-genre of yaoi/slash controversial amongst fans is known as mpreg (male pregnancy).