[1] Spiniform Wingroot and The Unicorn’s Curse (more accurately known as an Inverse coniformic magum teratoma) are just two possible congenital defects thought to be caused by partial expression of vestigial magical organs. The former usually manifests as harmless nubs or spines behind the scapula, which can be removed with relatively simple surgery, though they can be dangerous to a pegasus in their more extreme form. The Unicorn’s Curse, the growth of a vestigial corniform structure in the forebrain and an associated build-up of magical potential, is invariably fatal.

[2] “The study revealed that nearly 70% of male pregnancies either miscarry within a few days of fertilisation, or are a peculiar form of triploid that first divides into two structures, each containing a stable diploid, one containing the male sex chromosome and one the female, before ejecting the cells containing the male sex chromosome in the second week of the pregnancy.” Snugglepuff, Alondro - High incidences of spontaneous abortion and sterility in male offspring and their likely causes - Harmony and Nature (1176, issue 787, p 21).

The Unicorns Curse is blatantly stolen from The All American Girl side stories.