Sperm Spinning for Gender Selection
Several different techniques are all loosely referred to as "sperm spinning" because the semen is spun in a centrifuge as part of the process.
All of these methods originally claimed to separate X and Y-sperm, yet it has been shown in repeated, reliable experiments that this is simply not so; the X/Y sperm ratio remains 50/50 after the use of any of these methods. And although many experts say they're only good for "separating parents from their money," practitioners still claim significant success rates.
The best known of these is the patented Ericsson albumin method, and it may be the only sperm spinning method still promoted and widely available. I have included the other methods as well because they are all very similar, and every now and then I see a fertility clinic offering a vaguely described method for gender selection, which is probably a density gradient centrifugation or modified sperm swim-up.
Sperm Spinning Since the 1970s
For over 30 years, researchers have attempted to use centrifugation to separate X and Y-sperm. During centrifugation, rapid, controlled spinning causes particles in a liquid become sorted into layers, according to density; so it would seem to be perfectly suited for separating heavier, more dense X-sperm from lighter Y-sperm.
Accordingly, researchers began reporting experiments of spinning sperm in various types of solutions, and several initially reported promising success in creating X or Y-enriched samples.
However, it would later turn out that the method then used to test the resulting sperm samples, called quinacrine staining, was flawed. (This study showed that quinacrine staining "is not suitable for evaluation of methods that claim to separate X and Y-bearing sperm".)
With the later development of a reliable method to measure the X:Y ratio of sperm, called "fluorescence in situ hybridization" (FISH), repeated experiments showed that none of the proposed sperm spinning methods actually altered X:Y ratio of sperm. Yet surprisingly, a few studies reported that actual pregnancies and births after using sperm spinning techniques showed high success.
Sperm Spinning Safety
Sperm spinning techniques for gender selection are only minor variations on a standard procedure that is used to prepare sperm for assisted reproduction (IUI or IVF). The purpose of the procedure is to:
- Separate the sperm cells from the semen, or fluid. During normal intercourse, only the sperm cells, not the seminal fluid, enter the uterus. Semen in the uterus can cause contractions which prevent fertilization, or even a dangerous allergic reaction.
- Concentrate healthy, motile sperm.
- Filter out abnormal and immotile sperm cells and debris, such as dead sperm cells and bacteria that may impede fertilization.
The resulting sperm sample is much more likely to result in a successful pregnancy than if unprocessed sperm were used for insemination. Even when not used for gender selection, the procedure is sometimes referred to as "sperm separation" or "sperm sorting", because it separates the best sperm from low quality sperm.
Since sperm swim-up, and the percoll and albumin methods, are standard procedures for IUI and IVF, they are considered safe. Attempted gender selection is either an additional or modified step to these standard techniques, or in some cases, perhaps just a side-effect.