Sunday, August 17, 2014

Supposition about why baby Gammy has Down syndrome

Baby Gammy is a 7-month-old boy with Down syndrome born in Thailand to Pattaramon Chanbua, a surrogate mother. He was ordered by Australians David and Wendy Farnell and has a twin sister named Pipah. When it turned out during Ms. Chanbua's pregnancy that one of the twins she was carrying had Down syndrome, the Farnells allegedly wanted the fetus to be aborted in the 7th month. The surrogate refused based on her Buddhist faith. After the birth, the Farnells took the non-disabled baby girl and returned to Australia.

Gammy remained in Thailand with Ms. Chanbua, his legal mother. She received no child support of any sort and claims that the surrogate agency even did not pay her the entire sum promised before. She had to quit work to care for Gammy but could not afford proper treatment when he developed pneumonia. At that point, she told his story to the world.

The case made an international scandal, especially after it came to light that the biological father David Farnell is a convicted pedophile who has served two prison terms for sexually abusing young girls. Some even speculated that the true reason for leaving Gammy behind was not his disability but his gender. Now, the Thai junta is cracking down on the country's commercial surrogacy business, banning a service for everybody because of the transgressions of a few and leaving in limbo hundreds of parents and babies currently undergoing the procedure.

Let me disclaim that, while I am disgusted to my bones by the Farnells, I have no sympathy to the surrogate mother, either. I see her as just another religious fundamentalist forcing her pro-life views on others. This is of course a minority opinion; most people lavish praise on Ms. Chanbua. Australian immigration minister Scott Morrison called her "an absolute hero" and "a saint". The latter qualification immediately reminded me of Gianna Beretta Molla, who preferred death to abortion and was officially made a Catholic saint in 2004. I'd wish that people stop turning women into role models for the "achievement" of carrying to term a pregnancy in situations where the most sensible choice (or, as in Dr. Molla's case, the only sensible choice) would be to terminate it.

However, the villain in Gammy's story is undoubtedly the father David Farnell. His wife seems to have accepted from the beginning the role of being totally subordinate to him. When media first reported that she is "Asian-born", some commenters immediately said that she must be a Chinese mail order bride ready to do anything for an Australian visa. I am sorry that I initially scorned them - they turned to be absolutely right: Mr. Farnell married Wendy in China, her country of origin, and then brought her to Australia. She knows about his past but says that he is a good man who has just made some mistakes as everybody does. So I agree with those who think that David, unwilling to be charged again for abusing girls outside his family, decided to produce an object within the family, married Wendy to use her as a cover and went ahead to obtain a daughter.

There is a technique called Ericsson method to influence the sex of the embryo by sorting spermatozoa before insemination. It is based on the difference in mass between sperm cells that will produce girls (carrying a big X chromosome in their nucleus) and those for boys (carrying a small Y chromosome). The success rate of gender selection by this method is about 70%. Now, look at the graphic below.

It is from Seidel & Garner's 2002 article Current status of sexing mammalian spermatozoa published in the Reproduction journal. Pay attention that the far right part of the curve is occupied by "aneuploid, e.g. trisomic spermatozoa". Actually, these are spermatozoa that have an additional chromosome and if fertilize an egg, will produce trisomic embryos. Of course, having an additional chromosome will increase the mass and, if the cell is an X spermatozoon, will bring it to the far right end of the curve for X spermatozoa.

There is, however, another opportunity not shown in the figure: if a Y spermatozoon has an additional chromosome, it will bring it to the far right end of the curve for Y spermatozoa... which will be pretty much within the median range for X spermatozoa! In simpler words, preference for X spermatozoa that will produce female embryos is expected to enrich the sample not only with X spermatozoa but also with abnormal Y spermatozoa made heavy by an additional chromosome. The latter sperm cells will produce male embryos with trisomy - an additional 3rd copy of a chromosome, e.g. chromosome 21 in Down syndrome. So I suppose that David Farnell may have used the Ericsson method to increase the likelihood of having a girl because he is not interested in boys. This led to selection of an X sperm cell that produced Pipah, and a Y sperm cell with an extra chromosome 21 that produced Gammy.

My "hypothesis" of course is on thin legs. It is not truly verifiable, unless some person engaged in the procedure opens his mouth. I guess, however, that if Gammy's chromosome set is studied, it will turn out that his extra chromosome 21 is of paternal origin, rather than of maternal, as usual. In a more general sense, I guess that using the Ericsson method to select females will result in a slight but statistically significant increase of the rate of male trisomic embryos.

Anyway, I hope that Australian authorities will keep an eye on the Farnells and find some justification to take little Pipah away from them. Ericsson method or not, a child is hardly safe in the home of a man with 22 child sex convictions.

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