As I understand it myself, according to MN26, the five kinds of sensual stimulation (kāmaguṇā) are “sights known by the eye that are likable, desirable, agreeable, pleasant, sensual, and arousing”, and so forth for sounds, smells, tastes and touches.
Thus, I take them as synonymous with the five feelings (vedanā) that being pleasant (sukhā) arise from the contact (phassa) of visible form (“external” sense object, rūpā), eye (“internal” sense organ, cakkhu), and eye-consciousness (consciousness, viññāṇa), and so forth for the rest of contact (phassa) modes.
 That is to say, we can consider the five kinds of sensual stimulation as equal to the five pleasant feelings: kāmaguṇā = sukhavedanā.
Then, MN 26 says "There are ascetics and brahmins who enjoy these five kinds of sensual stimulation tied, stupefied, attached, blind to the drawbacks, and not understanding the escape. You should understand that they have met with calamity and disaster, and are vulnerable to the Wicked One.
I understand this as the craving (taṇhā) that coming from pleasant feelings (sukha vedanā = kāmaguṇā) has led to clinging (upādāna).
And it continues: “There are ascetics and brahmins who enjoy these five kinds of sensual stimulation without being tied, stupefied, or attached, seeing the drawbacks, and understanding the escape. You should understand that they haven’t met with calamity and disaster, and are not vulnerable to the Wicked One.”
I understand this as craving (taṇhā) coming from pleasant feelings (sukhavedanā = kāmaguṇā) that hasn’t led to clinging (upādāna), because of attention and seeing the drawbacks, and understanding the escape, etc.
 That is to say, feeling is a necessary condition for craving, which is a necessary condition for clinging, but not a sufficient one.
Taking in count these two considerations, how are we to understand this phrase in MN 123: “When the being intent on awakening is conceived in his mother’s belly, she obtains the five kinds of sensual stimulation and amuses herself, supplied and provided with them”?
In my previous message I said that “we should then understand that the only sense impressions she experiences are the likable, desirable, agreeable, pleasant ones, with no mention to the possible attachment to them”.
As you well said, though, she probably did experience the five kinds of sensory stimulation, meaning “pleasant feelings”, prior to conceiving. So I think I should explicitly have said “the only impressions or feelings she experiences during conception” are the pleasant ones.
Then we can guess about she being tied, supplied, or attached, etc. or, instead, not being tied, supplied, or attached to the five kinds of sensual stimulation during pregnancy. The text just says that “Seven days after the being intent on awakening is born, his mother passes away and is reborn in the group of Joyful Gods.” Take into account that Tusita still belongs to the sensuous world (kamaloka). [See the thirty one planes of existence].