Table 1.

Twin pregnancy rates and outcomes in rhesus monkeys following the transfer of intact or demi-embryos.

	Pregnancy rate per transfer (%)	Twinning rate per transfer (%)	Live birth rate per twin pregnancy (%)
Intract-embryos	14/57 (25)	14/70 (20)	18/28 (64)
Demi-embryos	12/55 (27)	1/12 (8)	0/2 (0)

The pregnancy rate was determined from transfers involving only two embryos. The twinning rate was based on all pregnancies (2 or more embryos/transfer) in the intact embryo group, hence the number of pregnancies is larger.