EVALUATING EFFECTS OF EXPOSURES ON EMBRYO VIABILITY AND UTERINE RECEPTIVITY IN IN-VITRO FERTILIZATION

We consider models for the occurrence of pregnancy following in vitro fertilization. In this clinical protocol, implantation depends on two factors: the receptivity of the uterus and the viability of at least o ne of the embryos transferred to the uterus. This work is motivated by the need to identify reliable bio-markers for these two factors, in o rder to enhance the success rate for couples undergoing this procedure . We present a general latent variable structure model for outcomes th at take either one of two possible forms: as summed Bernoullis, based on an ultrasound count of gestational sacs, or as aggregated Bernoulli s, based only on the outcome of a biochemical pregnancy test. We allow both uterine receptivity and embryo viability to be influenced by cov ariates. The proposed latent variable structure allows us to utilize t he existing statistical packages to maximize an otherwise intractable likelihood function. The method is sufficiently flexible to permit any valid choice of link function. We illustrate by applying the method t o a recent study of in vitro fertilization carried out in North Caroli na. The number of cells at transfer is evidently a marker for embryo v iability. (C) 1998 John Wiley & Sons, Ltd.