Hi, Chad here, from the States. I tried putting my very pregnant parva in a commercial breeder last night, but she got very stressed out and vomited up all her food. One thing I"ve found to help is to stuff the female with food the last few days before eclosion so she is less hungry when the time comes. My valid batches always have a 21 day gestation to the very day. With my other, premature-birth prone (about 14 -16 days) female the tads are "goofy", and few if any survive.
Chad