Hospital Bag Lists & Nightgowns

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So nearly every sample hospital bag checklist I've looked at includes a nightgown which it then says should be "ruin-able". Now  this has me wondering - do they mean a nightgown that I can wear during labor? Instead of a hospital gown? Because hospital gowns were not made with pregnant women in mind. I mean, I'm not about to waste money on one of those "custom made birthing gowns", but if I can wear a regular old nightgown to give birth in, I will happily waddle myself to the nearest Dollar General or Walmart and sacrifice $8 for my comfort and happily covered rear end. Can anyone confirm whether they will let you wear an ordinary nightgown to give birth?