A prediction model for selecting patients undergoing in vitro fertilization for elective single embryo transfer  Claudine C Hunault, M.D., Marinus J.C Eijkemans, Math H.E.C Pieters, M.D., Ph.D., Egbert R te Velde, M.D., Ph.D., J.Dik F Habbema, Ph.D., Bart C.J.M Fauser, M.D., Ph.D., Nicholas S Macklon, M.D., Ph.D.  Fertility and Sterility  Volume 77, Issue 4, Pages 725-732 (April 2002) DOI: 10.1016/S0015-0282(01)03243-5

FIGURE 1 Probabilities of pregnancy and twin pregnancy in relation to female age and development stage of the best two embryos available for transfer. Graphs are given for ET on the third and fifth day after oocyte pickup and for three combinations of embryos with identical developmental stage scores. A developmental stage score of 3 denotes top quality and a score of 1 denotes poorest quality still suitable for transfer. A score of (3, 3) means the combination of two embryos both scored advanced; (2, 2) means appropriate; and (1, 1) means retarded. Examples of how the graphs may be used to estimate relative chances of singleton and twin pregnancy are given in the text. Line a = probability of pregnancy if two embryos are transferred. Line b = probability of pregnancy if one embryo is transferred. Line c = probability of singleton pregnancy if two embryos are transferred. Line d = probability of twin pregnancy if two embryos are transferred. X = patient age below which SET will result in a higher chance of singleton pregnancy than transfer of two embryos. Hunault. A prediction model for IVF. Fertil Steril 2002. Fertility and Sterility 2002 77, 725-732DOI: (10.1016/S0015-0282(01)03243-5)