Sleeping through baby cries anyway

i’m 18 weeks pp and my so sleeps through everything, even when our lo is crying. it’s hard for me to understand how he can just sleep through it… does anyone else have a partner who sleeps like this? how do you handle it?

how someone can sleep through a baby crying is a physiological question, not a behavioral one, at least initially, bc individual auditory arousal thresholds during sleep vary widely, and some brains are simply better at gating out non-threatening external stimuli without fully waking. this isn’t a conscious choice, it’s a variance in sleep architecture and sensory processing that can be exacerbated by existing sleep debt, making deeper sleep even harder to disrupt.

His sleep stages might just be much deeper right now.