I’m not really a fan of Tracy Borman, honestly? But I’ve never read that book so I can’t judge it.
Have talked more about this theory here. I remain pretty skeptical of it. If we look at the pregnancy-to-full-term and miscarriage patterns of Bessie Blount, Anne Boleyn, and Jane Seymour alone (as in…their first children by Henry were to term) the theory makes sense. When we look at COA’s, however, it doesn’t:
[Mary] wasn’t Katherine of Aragon’s first child; Katherine’s previous four children all died in the womb or soon after birth. If Henry did carry the big K antigen, he likely passed it on to one of Katherine’s first four babies, and Katherine would have developed antibodies to it, devastating her later pregnancies. Mary never would have been born…. “Katherine of Aragon’s initial
miscarriages and perinatal deaths, followed by a
successful fifth pregnancy are not typical of Kell antigen
sensitivity.”
We also don’t know, in the case of Blount and Seymour, if they would’ve had pregnancies by Henry that ended in healthy births because their first children by Henry were also their last.
I think the theory became popular because it doesn’t make sense if we look at fertility (or not really even fertility, as there were technically several pregnancies by him in his lifetime but…births to full-term, rather) as a genetic…sort of inheritance? Elizabeth of York and Henry VII had several children, so why would Henry VIII not? Elizabeth Woodville and Edward IV did the same. Ferdinand and Isabella also did, Elizabeth and Thomas Boleyn had three children that survived to adulthood, etc. So, Henry VIII must have simply been unlucky enough to have the Kell positive blood type.
The Kell theory also links into McLeod’s to explain his behavior and mental state later in life, but proves inconsistent in signs of McLeod’s:
However, although Henry displayed significant behavioural
change, he was not reported to have a neurological
movement disorder such as epilepsy, and his chronic leg
ulcer caused considerable pain, arguing against a sensory
neuropathy.
I think the theory disregards other factors that could have led to miscarriages and stillbirths. The Tudor diet was not the best (although the diet of Queen Consorts was far more nurtitious and plentiful than the majority of England at the time); and as the water was not safe to drink alone, women drank watered-down ale or wine throughout the duration of their pregnancies.
Given contemporary description, it is also possible that Anne Boleyn was underweight. Underweight women are generally at a greater risk of miscarriage.