It's thankfully not life-threatening.
Of course, because it's not life-threatening, the insurance refused to pay for the sleep study. They will, however, pay for her surgery to correct it.

My lingual tonsils were the size of plums. Infected with a very nasty staph infection that antibiotics couldn't treat. There were structural issues as well, that are mostly fixed. I can sleep without the CPAP, although I rarely do, without fear of death. Once I lose the weight, I should be okay.
As for my son, it was technically SIDS. But since SIDS is defined as an infant's death that has no explanation, I find sleep apnea to be the likely culprit. The age most likely to be hit by SIDS, 2-4 months, is also the time when the baby starts gaining voluntary control over breathing. It's also the time when sleep apnea is at its most severe.