A lotus birth is leaving the umbilical cord and placenta attached to baby until it naturally falls off. Many tribes/cultures do this, it is nothing new. It is done in some tribes as a survival thing, other tribes do it as a spiritual thing.
The benefits would be the same as leaving the cord attached until it stop pulsating to give the baby all the blood, iron and oxygen he/she needs. Some also say the cord of a lotus birth comes off much more smooth and sooner than the cord of the stump when cut. Most people I know who have done that do it as a more spiritual ritual than anything else.