Embryos are tiny, delicate things. As such, the transfer process is often conducted with great caution and preparation. This caution can often cause surrogates to be quite concerned about how to best protect the embryo they’ve been entrusted with carrying. It is normal for intended parents to feel some degree of concern, too. In fact, many will raise the question of how secure the embryo is once placed in the uterus, and if it’s possible that the embryo could “fall out.”
The fear is that walking, jumping, showering, or even urinating could cause the embryo to simply slip out of the uterus. Doctors often prescribe bedrest following the transfer in order to allow the embryo time to get settled and implant, so to many it makes sense that undue movement could cause the embryo to become dislodged and slip out. Rest assured that this is highly unlikely. The idea has merit, in theory, but is not plausible in reality.
The uterus is a muscular organ. This means that it stays contracted and tight in its natural state. While the area inside of the uterus is called a “cavity”, it is not a literal empty space. The transferred embryo does not have open space in which to move freely or roll around. Nearly all IVF doctors will require the surrogate’s uterine lining to be thick enough for the walls to touch in the middle before proceeding with a transfer. This creates an environment in which the thick, sticky endometrial lining leaves no empty space. When the embryo is placed between the uterine walls and the muscle contracts, it will create a secure place for the embryo to bury itself deep within that thick lining and begin to grow.
Visualize placing a poppy seed in the crease of your elbow, and then folding your arm shut tightly by using your muscle. Now wiggle that arm as hard as you can. No matter how hard you try, that poppy seed will not fly out. An implanted embryo inside of a flexed uterus is much the same.
No reasonable external physical activity, be it jumping, rolling over in bed, walking, or running can cause a healthy receptive embryo to become dislodged once it has implanted into the endometrial lining. The bedrest period is meant to help the surrogate relax and encourage the embryo to implant and bury itself within the endometrial lining. Different doctors have different protocols, and surrogates will adhere to the guidelines they are given, but the science will remain constant regardless of the protocol. Once that embryo is implanted, it is highly unlikely for it to dislodge.