The amount of blood a woman loses after a water birth is about the same as the amount you would lose if you were not in the bath. One recent study actually measured the average loss at about 300mls (most women will lose 200 to 400 mls after a vaginal birth). A caregiver experienced with water birth can usually have a general idea about 'how red' the water should be, with water birth estimates being either 'above or below' 500mls.
There is no evidence to suggest there is any problem with delivering your placenta in the bath. In fact one study that made all the women get out of the bath for the placenta, found that sometimes the placenta came away 'in transit' resulting in a heavier blood loss. There was one theory put forward in the 1980's that water could get up inside the uterus, as the placenta was born, causing complications. This has never happened and remains just that - 'a theory'. If you or your caregiver feel uneasy about delivering the placenta in the bath, it may be easier to pull the plug or lie on a rug or mat just beside the bath, or stand up to give birth to the baby above the water, rather than make your way to the bed, unless it is close.
The temperature of the water
It is now believed the ideal temperature of the water should be about body temperature, that is about 37
o Celsius. It was once a concern that cool temperatures (less than 35
o C) could stimulate a gasp reflex (although there are documented cases of women giving birth in the Black Sea).
In response to this possibility caregivers in the UK erred on the side of 'safety' maintaining pool temperatures at levels between 37- 39
oC. However in 1993 two babies were born in distress (neither were water births) after their mothers had spent long hours in hot water. Both recovered well but it was reasoned that because babies' temperatures are always about 0.5 - 1
oC above the mother's (so if the mother was 39
o C, the baby would be up to 40
o C).