Apparently, on week 17 of gestation: "The fetus still has thin skin, but will start to put on fat. Its skin is covered with a whitish coating called vernix. This “cheesy” substance is thought to protect fetal skin from long-term exposure to amniotic fluid" Source: https://my.clevelandclinic.org/health...
To listen while using other apps, switch the player to Picture-in-Picture (PiP) during playback — it keeps playing in a small floating window (the screen stays on).
To listen with the screen fully off, in-browser playback stops by YouTube's design. Open the video in the YouTube app to keep listening where background playback is supported (e.g. with YouTube Premium).
Open in YouTube app