Rotational cleavage in mammals occurs at division:
Mammalian cleavage is holoblastic and rotational pattern uniquely observed. First division is meridional producing two blastomeres. Second division shows rotational orientation where one blastomere divides meridionally and sister divides equatorially, resulting in orthogonal spindle axes producing transient asymmetry and slight asynchrony. This pattern from second cleavage onward distinguishes mammals from other vertebrates. Rotational divisions generate blastomeres with different inherited polarity cues influencing subsequent lineage allocation to inner cell mass versus trophectoderm, establishing early embryonic-abembryonic axis formation, initial patterning events and cellular heterogeneity for differentiation.
Ref: Gilbert, Developmental Biology, 12th ed., Chapter 12: Rotational cleavage pattern in mammalian embryos and blastomere polarity.