Probabilities for singleton and multiple pregnancies after in vitro fertilization.
OBJECTIVE
To help physicians provide risk estimates for specific pregnancy outcomes.


METHODS
Computation of exact binomial probabilities for singleton and multiple pregnancies as a function of two inputs: the number of embryos transferred and the implantation rate. Inputs were varied over the range of values reported in the literature.


METHODS
Probabilities for a singleton pregnancy (none), a multiple pregnancy (Pmult), and no pregnancy (Pnone) after one IVF cycle.


RESULTS
Given a 30% implantation rate and three embryos transferred, Pone=.44, Pmult=.22, and Pnone=.34. Although further increasing the number of embryos transferred increases the chance of pregnancy, it also raises the probability of a multiple pregnancy and lowers the chance of a singleton pregnancy. Although varying the implantation rate changes the specific probability estimates, the same trade-off persists.


CONCLUSIONS
Those who consider an IVF "success" to be a singleton pregnancy should be attentive to the number of embryos transferred. Infertility therapy may be one area in medicine where more is not necessarily better.
The Reproductive Science Center of Boston, Waltham, Massachusetts, USA.
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Martin
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Welch
D000328:Adult; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D011256:Pregnancy Outcome; D011272:Pregnancy, Multiple; D011336:Probability; D012307:Risk Factors