More evidence of genetic basis for cot death

Genetic mutations that affect vital body functions are linked to an increased risk of cot death, a new US study shows. Researchers at the Rush University Medical School in Chicago studied DNA from 92 babies who had died of sudden infant death syndrome (SIDS), and 92 healthy babies. They looked at genes involved in the development of the autonomic nervous system, which controls processes such as breathing and heartbeat, and found that mutations in these genes were far more common in the SIDS cases, particularly in African American babies.

The scientists found 11 different mutations in 14 of the SIDS cases, but only one mutation in two of the healthy babies. Team leader Debra Weese-Mayer said that 71 per cent of the SIDS cases that had the mutation were African-American, as were both of the healthy babies. "Knowing that SIDS incidence is significantly higher in African-Americans gives strong support for the possibility of a genetic basis," she concluded. She thinks that mutations affecting regulation of the nervous system may mean that heart and breathing rate may not be able to react quickly enough to a stressful situation, causing these functions to "simply shut down".

The study, published in the journal Pediatric Research, sheds further light on the possible underlying causes of SIDS. Education campaigns in both the US and UK to teach parents to put babies to sleep on their backs has reduced the number of SIDS cases, but has not eradicated them. "We've had too many parents who came to us and said "look, we did everything right – we got the best prenatal care, no-one smoked anywhere near the baby, we put her down on her tummy and still she died," said Weese-Mayer, adding "that led us to say there has to be a genetic basis."

Earlier this year, another US team identified a gene mutation linked to cot death and genital malformation in an American Amish community, which also affected control of the nervous system.

Sex selection

Boys or girls? A technique for choosing the sex of children created using fertility treatments has been available in the UK for a number of years, if it is used to avoid a serious medical condition. But with more simple techniques now available, should sex selection for "social" reasons, such as family balancing, also be allowed?

The sex of a child is determined by the sex chromosome carried by the sperm. Men produce sperm bearing either an X or Y chromosome, whilst women produce eggs that all contain one X chromosome. If a sperm bearing an X chromosome is united with the X from the egg at fertilisation, this will result in an "XX" pregnancy that produces a female baby. If a sperm bearing a Y chromosome fertilises the egg, an "XY" pregnancy will result, giving rise to a male child. Using in vitro fertilisation (IVF) with preimplantation genetic diagnosis (PGD), early embryos can be tested to determine what set of chromosomes they carry and, consequently, either male or female embryos could be selected for implantation. In this way, diseases caused by a faulty gene on the X chromosome, which usually only affect boys, can be avoided.

Early in 1993 the London Gender Clinic opened, allowing parents to choose the gender of their children. This was not done by testing IVF embryos for their sex as in PGD, but by a technique involving the separation of male and female sperm by centrifugal force. Although this was not illegal, it prompted one UK politician to seek to prohibit any kind of sex selection in assisted conception clinics, and sparked debates that continue to this day. In response, later in 1993, the Human Fertilisation and Embryology Authority (HFEA) issued a public consultation document on sex selection, the outcome of which was a ban on social sex selection using the techniques regulated by the Human Fertilisation and Embryology (HFE) Act 1990. Sex selection for medical or health reasons, for example to avoid X-linked diseases such as haemophilia or Duchenne muscular dystrophy, was still allowed.

News developments

In March 2000, a Scottish couple whose only daughter died following a bonfire accident applied to the HFEA for permission to try and conceive a baby girl using IVF. Louise and Alan Masterton, who had four boys aged between nine and 15, wanted to use PGD to choose the baby's sex. Mrs Masterton had been sterilised after the birth of her daughter Nicole, who was three years old when she died in July 1999. The couple decided to use IVF to try for a baby girl, by removing Mrs Masterton's eggs and fertilising them with Mr Masterton's gender-sorted sperm. But sperm-sorting is not 100 per cent effective, so the couple also requested PGD, to ensure that only female embryos were put back into Mrs Masterton's womb. The HFEA told the Mastertons that it would consider their request if they made an application through one of the five IVF clinics in the UK with the necessary expertise.

After being turned down by all the clinics they approached, in October 2000, the Mastertons launched a court action under the Human Rights Act to win the right to choose their baby's sex, saying their case had not been given a fair hearing, which they claimed was a breach of Article 6 of the Act. They also planned to argue their case under Article 8, which gives the right to respect for private and family life. Their claims later proved unsuccessful. In March 2001, the Mastertons revealed that they had travelled to Italy the previous July to undergo a sex selection procedure, but that it had not resulted in any female embryos.

At the annual meeting of the European Society of Human Reproduction and Embryology (ESHRE) in July 2001, a team of US scientists from the Genetics and IVF Institute in Fairfax, Virginia reported that they had devised a new method of laser sorting sperm by gender. The technique, called MicroSort, is said to greatly increase the number of female embryos created in IVF in comparison to previous sperm sorting methods, and is said to be accurate in about 90 per cent of cases. The MicroSort technique relies on the fact that the X chromosome carries more DNA than the Y chromosome, and is therefore heavier. In a "modified flow cytometer instrument", most of the heavier sperm can be separated from the lighter sperm, after being dyed with a fluorescent marker and fired at high speed under a laser. At the conference, Dr Harvey Stern said that although the technique was still in the trial stage, it "substantially increased the chance of a couple having a child of a particular gender". He reported that, at that time, 297 pregnancies had been achieved using the technique, and that 187 babies had been born.

In October 2001, the UK government asked the HFEA to investigate a "legal loophole" which in theory allowed some private clinics to offer sex selection for non-medical reasons. The request came following reports that some UK clinics were offering a sperm sorting technique. Because sperm sorting does not involve the creation of an embryo or the storage of sperm, it is not controlled by the HFE Act 1990. The authority said that it would re-examine its policy on this matter.

The debate reignited again when, in September 2002, the Observer, one of the UK's Sunday newspapers, published a report claiming that sex selection techniques were available commercially for British and other couples at a fertility clinic in Belgium. Located in Ghent, the clinic was said to offer a sperm sorting service – which involved a sample of sperm being taken and frozen before being sent to the MicroSort laboratory in the US – for "family balancing" for couples who already have children of one sex, but who want to ensure that their next child is of the opposite sex. The technique was not illegal, but it did raise concerns that people were trying the method before all the potential effects of it were known. Once the sorting procedure was finished, the sorted sperm was returned to the Belgian clinic, where it was used in IVF procedures. The Ghent clinic claimed the technique was 91 per cent effective if a girl was wanted, and 75 per cent for a boy. It was also reported that six British couples had travelled to America to take advantage of MicroSort at the Genetics and IVF Institute in Virginia.

In October 2002, the HFEA launched a second public consultation asking whether embryo sex selection techniques should be made available for non-medical purposes, such as "family balancing", and whether sperm sorting should be regulated in the UK by the HFEA. Since the previous consultation in 1993, more efficient techniques for sperm-based sex selection, such as laser sperm sorting, have been developed. In any case, because UK assisted conception regulations currently only cover the use of embryos and of frozen or donated sperm, a sperm sorting clinic – using fresh sperm – could in theory be opened and operate without the HFEA having any regulatory control over it. By 2002, following various reports about the use of sex selection abroad and increased success rates, the HFEA had recognised that public opinion might have changed, especially if the treatments were perceived to be safe and the circumstances in which they could be allowed to take place were carefully controlled.

In September 2003, a debate on sex selection was held at the British Society of Human Genetics (BSHG) annual conference. Around 80 per cent of the 204 professional geneticists attending the debate voted against carrying out sex selection for social reasons, with 18 per cent voting in favour, and two per cent abstaining.

The results of the HFEA consultation were made public in November 2003, just two weeks after it was reported that Nicola Chenery, a UK woman who travelled to Spain to conceive a female child, had given birth to twin girls. Nicola and her husband Mike already had four sons, so paid six thousand pounds to use IVF treatment with PGD to determine the gender of their next child. Sex selection is permitted in Spain for family balancing, as well as for medical reasons. "We are thrilled, and have no regrets about going abroad for such a wonderful outcome", Mrs Chenery told a UK newspaper.

Based on the consultation – which took into account the views of members of the public and experts, and the results of research into scientific, technical, social and ethical issues – the HFEA made its recommendations to the Government. These included recommendations that the current ban on sex selection for non-medical reasons be continued and that sex selection techniques involving sperm sorting should become regulated in the UK in the future. Roughly 80 per cent of the 600 respondents had said that they did not believe that sex selection techniques should become available for non-medical purposes. Suzi Leather, chair of the HFEA, said: "The HFEA has to balance the potential benefit of any technique against the potential harm", adding "we are not persuaded that the likely benefits of permitting sex selection for social reasons are strong enough to outweigh the possible harm that might be done". Critics said that those parents who wanted to use sex selection for non-medical reasons would simply be forced to go abroad for the treatment.