in SciFinder 3157 papers and patents are published on ivy, but no study was conducted for pregnancy.
but I found one article "Ethnoveterinary medicines used for ruminants in British Columbia,Canada by Cheryl Lans, Nancy Turner, Tonya Khan, Gerhard Brauer, and Willi Boepple. who claim the veterinary use of ivy for retained placenta.
How much saponins are safe during pregnancy?