1978 was a historic year for human reproductive technology as it marked the birth of the first “test tube baby”. Since then, the science of fertility treatments has become an essential part of our mainstream world. But, like all scientific developments, it has also been the subject of myths and misconceptions, new leaps in procedures and shifts in affordability. Perhaps the most pervasive myth surrounding what we now refer to as In Vitro Fertilization, or IVF, is the stubborn belief that IVF treatments result in prolific plural pregnancies. However, according to most reputable fertility authorities, including representatives for the New York based Center For Human Reproduction, the likelihood of plural pregnancy is most directly connected to non IVF fertility treatments.
While the rate of multiple births has declined by nearly 30% in the last few decades, it is important to understand what might affect your chances of starring in your very own version of Me and Kate Plus 8. Until fairly recently the majority of embryonic transfers were done on the third day after fertilization. This stage, where the embryo has just 4 to 8 developed cells, is called the “cleavage stage”. Unfortunately for these fine petri dish protégées there is no clear way to determine which, if any, will continue on to become viable. Thus we have the tendency to implant many in the hopes of boosting the odds of one succeeding.
But, now, thanks to new culturing techniques, 5-7 day embryos can be used. Called Blastocysts, 5-7 day embryos will have had time to “hatch” into 2 distinct cell groups (placenta and fetus). The ones that do so can be selectively implanted into the mother’s uterus in smaller numbers. Since scientists can already begin to determine which ones are more likely to continue development (information that is unavailable in the cleavage stage groups), they can isolate and place their bets on individual embryos. This option is not available in all cases of IVF, but has contributed dramatically to a significant reduction in multiple births in some populations, especially younger donor and recipient patients.
In 2012 The Human Fertilization and Embryology Authority, a branch of the UK Department of Health, produced a 4 year research analysis project evaluating the results of this shift towards smaller batch blastocyst implanting. They reassuringly concluded that, “The pregnancy rates from elective single embryo transfer are similar to the pregnancy rates from double embryo transfer”, and that the rate of multiple births continued to drop substantially with the implantation of fewer embryos (from 24% in 2009 to around 10% in 2012). Research being conducted in the United States traces the rise of single versus multiple births to the revised guidelines released in 2009 by the American Society for Reproductive Medicine (ASRM) regarding the appropriate maximum number of embryos allowed for transfer. Continuing to refine lab procedures used in embryonic selection, freezing and cultivation, as well as reductions in age of both donor and recipient, is predicted to continue elevating trends of single IVF births.
While pregnancies resulting from IVF are less likely than ever to produce a big litter of kiddies, for reasons not fully understood, they are still slightly more likely to give you twins than traditional methods of conception. This, and all aspects of your fertility care, should be discussed with your doctor when evaluating your unique circumstances.