1. Probabilities for singleton and multiple pregnancies after in vitro fertilization 
Peter M. Martin, M.D., H.Gilbert Welch, M.D. 
Fertility and Sterility 
Volume 70, Issue 3, Pages (September 1998)
DOI: /S (98)

2. FIGURE 1
Trade-off of the probability of no pregnancy versus a multiple pregnancy as the number of embryos transferred increases, assuming a 10% implantation rate (top), a 30% implantation rate (middle), and a 50% implantation rate (bottom).
Fertility and Sterility  , DOI: ( /S (98) )