Within a few hours after retrieval, our embryologist will be preparing to fertilize the eggs. This may be done with either traditional IVF or with ICSI. In the former a high concentration of sperm is placed around each egg and they are left together overnight to allow “natural” fertilization to take place. With ICSI – intracytoplasmic sperm injection – we actually inject a single sperm into each egg. Our overall fertilization rate with ICSI has been over 80% of mature eggs fertilized. The fertilization rates with traditional IVF are only slightly lower. In any event, we will not look at the eggs again until the next morning at which time we will determine whether or not fertilization has occurred. Results of fertilization are discussed with our patients the next day.

Over the next 48 hours the fertilized eggs – now called embryos – will be left alone in the incubator. The less we disturb them, the happier they are. However, embryos will only grow in incubators for 3 to 5 days. At this time, they must be transferred back into the uterus. Embryo transfers may be done either on the third day after retrieval (day 3 transfer) or on the fifth day (referred to as a blastocyst transfer). Whenever possible we attempt to do a blastocyst transfer. However, this is not always feasible and Dr. Springer considers a number of issues before making this decision. On the day of the transfer, the embryos will have been carefully examined by both our embryologist and Dr. Springer. The decision regarding the number of embryos to transfer is not always easy and depends on such things as patient age, past IVF cycles and the quality of the embryos. The number of embryos to transfer is always a joint decision between doctor and patient. Our objective is to maximize the chance of pregnancy while minimizing the chances of multiple pregnancies – especially triplets or more.