Uh no sorry. Your info is wrong.
The comparison usually cites Anne Fausto-Sterling’s 2000 paper (Blackless et al., “How Sexually Dimorphic Are We?”), which estimated that about 1.7% of births deviate from a “Platonic ideal” of male or female dimorphism at the chromosomal, gonadal, genital, or hormonal level. Media and advocacy groups often equate this to red hair prevalence.
Intersex +1
The bulk of that 1.7% comes from conditions that most medical sources do not classify as intersex in the sense of sexual ambiguity or discordance:
Late-onset / non-classic congenital adrenal hyperplasia (LOCAH/NCCAH) alone accounts for about 1.5 percentage points. Affected people are typically unambiguously male or female at birth (matching chromosomes and phenotype); the condition mainly involves milder hormonal effects that often appear later.
Other major contributors include Klinefelter syndrome (XXY, typically male phenotype) and Turner syndrome (XO, typically female phenotype).
Fausto-Sterling’s own paper noted that the number who might receive “corrective” genital surgery is far lower (roughly 1–2 per 1,000). A 2002 peer-reviewed response by Leonard Sax in the Journal of Sex Research applied a stricter, clinically relevant definition—conditions in which chromosomal sex is inconsistent with phenotypic sex, or the phenotype is not classifiable as male or female—and arrived at about 0.018% (roughly 1 in 5,500). That is nearly 100 times lower than 1.7% and far below red-hair rates.
Realityslaststand
Other relevant figures
Babies born with genitalia ambiguous enough that a specialist is typically called: about 1 in 1,500 to 1 in 2,000 (~0.05–0.07%).
True ovotesticular DSD (“true hermaphroditism” with both ovarian and testicular tissue) is much rarer still (on the order of 1 in 20,000+).
Self-reported figures (e.g., New Zealand census) and some broad ICD-code studies produce intermediate numbers, but they still depend heavily on definition and do not support the “as common as redheads” framing under standard clinical criteria.