Victor Ivachnenko, MD1, Ksenia Krasnopolskaya, MD, PHD1, Michael Allon, MD2 and Dmitri Dozortsev, MD, PhD2
1. MONIAG, Moscow, Russian Federation 2. Advanced Fertility Center of Texas, Houston, USA
Introduction
The desire to select a gender of a future child is surprisingly common across different cultures 1,2,3. Even though a small minority of 3-5% have preference for the gender of the first-born, about half of the families would like to select the gender of the second child to have a "balanced" family with a boy and a girl 1,2,3,4.
There are only two scientifically proven techniques for choosing gender prior to pregnancy: testing embryos created in vitro using molecular probes - Preimplantation Genetics Diagnosis (PGD)5 and sperm sorting using MicrosortTM 6 (no longer available in the United States) or a combination of both. It has to be noted that even though gender selection employs technology identical to the one used in PGD, it is more accurately referred to as "sexing" because gender is not a disease.
Sexing using PGD offers the highest chance of accurate gender selection, close to 100%. The downsides of PGD is that it requires a woman to undergo an In Vitro Fertilization cycle, which can be physically and emotionally demanding as well as costly with prices upward of $10,000.
Because scientifically proven methods are so expensive, there is a number of less validated ways to increase the chance of having a baby with the desirable gender. One of the most common techniques is a so-called Shettles approach, which is based on the assumption that sperm cells have different effective life-span due to carrying X (female) or Y (male) chromosome. Therefore, intercourse 2-3 days before ovulation is more likely to result in boy than in a girl. Some of the published scientific studies support this claim 7, while other refute it 8. All studies trying to determine whether the male sperm life-so far Those studies are based on calculating newborns boy/girl ratios after the intercourse before and after ovulation. However, there are two intrinsic issues that may call the conclusions of those studies into question: timing of ovulation is difficult to assert and the size of the samples is limited.
The present study was designed to directly answer the question of whether male sperm cells survive longer.
Design
In order to verify whether the sperm cells of a particular gender have a preference in survival over time, we compared the proportion of X and Y bearing sprematozoa, soon after ejaculation and 10 days after in vitro culture. The comparison was made only between sperm fractions with identical motility. In other words, the percentage of the motile sperm cells in control and experimental group was about the same at the time of testing.
Material and Methods
Freshly collected sperm samples from a sperm donor were processed using Percoll gradient (Vitrolife, US) and the resulting suspension contained 90% of motile (live) sperm cells. At this time, an aliquot of this suspension was fixed on a slide using previously described fixation technique 9 and the ratio of X and Y bearing sperm cells was evaluated using Fluorescent In Situ Hybridization (FISH) to serve as a control. The rest was left at room temperature for 10 days. The motility of the sperm cells by this time was reduced to 45%, which means that only about half of the sperm cells in the sample remained live. On day 11, motile sperm cells were isolated using side migration technique10 and were collected using a micropipette under control of inverted microscope:
[video:http://www.youtube.com/watch?v=mmZlmV4poJ8&feature=youtu.be]
Collection of motile sperm using side-migration technique after 10 days of incubation in vitro.
The motility of the collected sperm was above 90%. The sperm was transferred on the slide and processed in the same way as the control to determine the ratio of X and Y bearing sperm cells using Fluorescent In Situ Hybridization (FISH) with XY probes mixture (Vysis, US).
Results
A total of two thousand sperm sperm cells has been scored in 2 separate experiments. The ratio of X (female) and Y (male) bearing spermatozoa in the population of sperm cells that have survived after 10 days was 48.9/51.1% and has not changed compared to the control 52.5/47.7 (p>0.1).
FISH to determine a ratio of male to female sperm cells after 10 days of incubation in vitro. X (female) - red, Y (male) - green. Nuclei are counter stained with DAPI.
Discussion
Our results clearly demonstrate that Y-bearing sperm cells have no advantage in their survival compared to X-bearing sperm cells. This suggests that trying to time intercourse prior ovulation will not increase a chance of conceiving a boy or a girl. It seems that there is no easy way to change a chance for conception with a particular gender.
References
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