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Girl or
boy?
It's in dad's genes
Alison Cranage
Progress Educational Trust
16 December 2008
[BioNews, London]
New research hints that whether a man has
sons or daughters is influenced by his genes. The study, by Mr Correy
Gellatly from Newcastle University, was published in the journal
Evolutionary Biology last week.
Mr Gellatly looked at 927 family trees from
Europe and North America, detailing over 556,387 people, dating back to
1600. He observed that a man with many brothers is more likely to have
sons, while a man with many sisters is likely to have more daughters. This
effect was not seen in women.
The sex of a baby is determined by its
father's sperm, an 'X' sperm (after the version of the sex chromosome it
carries) makes a girl and a 'Y' sperm a boy. Mr Gellatly hypothesises that
there is a gene, only active in males but a version of which is inherited
from both parents, which determines the ratio of X and Y sperm a man
produces.
He also suggests such a gene could explain
the increase in baby boys being born after World War I. Mr Gellatly
explains that the odds were in favour of men with more sons seeing a son
return from the war. This would mean such men were likely to have sons, a
trait inherited from their father. In contrast men with more daughters may
have lost their only sons in the war, and those sons would have been more
likely to father girls.
Other explanations have been proposed as to
why the birth rate is not 50:50 in certain couples. It has been suggested
that the sex of a baby could be influenced by differences in the time in a
woman's monthly cycle sex happens, or the amount of time sperm spends in
the testicles. Mr Galletly's study indicates there is a genetic component.
He says the net effect of such a gene is to
balance out the population: 'If there are too many males in the
population, for example, females will more easily find a mate, so men who
have more daughters will pass on more of their genes, causing more females
to be born in subsequent generations.'
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Research links intelligence to
sperm quality
Katy Sinclair
Progress Educational Trust
16 December 2008
[BioNews, London]
Researchers at London's Institute of
Psychiatry have found that more intelligent men have better quality sperm,
suggesting a correlation between intelligence and evolutionary fitness, in
a study published in the journal Intelligence.
The research team embarked on the study to
test the hypothesis that more intelligent people were healthier, not only
due to lifestyle factors, for example that brighter people are less likely
to smoke, but in an underlying genetic sense. Some research has rather
controversially suggested that intelligence and sperm quality are linked,
which historically has served the purpose of putting clever men at an
advantage in reproductive terms.
The study analysed 425 former US soldiers,
who had served in the Vietnam War, and who had provided semen samples and
undertaken intelligence tests. After adjusting for lifestyle factors, it
was found that the more intelligent men both had more sperm and sperm that
could swim better. Researcher Rosalind Arden stated, 'we found a small
positive relationship: brighter men had better sperm. This association
wasn't caused by habits like avoiding smoking or drinking - the big
hitters of health'.
However, researchers have emphasised that
the relationship between intelligence and sperm quality is small, and that
it does not mean that bright men are more likely to have more children,
nor that undertaking brain-training games was likely to improve sperm
quality. Arden commented, 'this does not mean that men who prefer Play-Doh
to Plato always have poor sperm: the relationship we found was marginal'.
Meanwhile, the team are now interested in
the relationship between overall physical health and intelligence, the
'fitness factor' idea, which suggests that there might be an underlying
relationship between many genetic factors in order to improve chances of
longevity and reproduction. 'We were interested in testing the idea that
if most of our genes act on many characteristics there might be a weak but
discoverable relationship right across all of our characteristics - from
nose to toes', explained Arden.
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Study shows
passive smoking causes fertility problems
Katy Sinclair
Progress
Educational Trust
11 December 2008
[BioNews, London]
Research published by
scientists at the US University of Rochester Medical Centre in the Journal
of Tobacco Control reveals that women exposed to second-hand smoke as
children or young adults have an increased likelihood of experiencing
miscarriages or trouble conceiving.
The research team studied
4,800 women treated at the Roswell Park Cancer Institute in New York, who
were asked to give details of their pregnancies, miscarriages, smoking
history and whether they were exposed to second-hand smoke at any points
in their lives. The team found that those exposed to send-hand smoke for
six or more hours per day in the past had a 68 per cent increased chance
of miscarriage or experiencing problems getting pregnant, as compared to
women who had never been exposed to second-hand smoke.
Luke J Peppone, a research
assistant at the James P Wilmot Cancer Centre at Rochester, commented: 'we
all know that cigarettes and second-hand smoke are dangerous, breathing
the smoke has lasting effects, especially for women when they're ready for
children'.
Four out of five women
taking part in the study had been exposed to second-hand smoke at some
point in their lives, and half grew up in a home with smoking parents. Of
those women whose parents were smokers, the study found they were 26 per
cent more likely to have difficulty conceiving and 39 per cent more likely
to have miscarried. Peppone called the results 'breathtaking', and stated
that the study, 'certainly points to yet anther danger of second-hand
smoke exposure'.
Scientists believe that
second-hand smoke causes changes in hormonal action relating to fertility
and pregnancy and that it can affect the cervix. In the past links have
been found between smoking and sudden infant death syndrome, miscarriage
and birth defects. Despite the warnings, an estimated 15 per cent of
mothers continue to smoke during pregnancy, and approximately 43 million
US women are exposed to others' smoke.
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Fertility
patients' indecision about fate of stored embryos
Sarah Guy
Progress Educational Trust
11 December 2008
[BioNews, London]
A study undertaken in the
US has revealed that fertility patients with frozen embryos in storage are
unhappy with the options available in relation to embryo disposal. Anne
Drapkin Lyerly MD, an obstetrician/gynaecologist and bioethicist at Duke
University was lead investigator of the study published online in
Fertility and Sterility. She said of patients in this situation that, they
'have had hard times thinking about destroying their embryos when they are
emotionally and financially invested in trying to make a baby'.
1,020 fertility patients at
nine clinics were canvassed for their thoughts about what should happen to
embryos created during IVF processes and stored when they were not used.
Only about two-thirds said that they were likely to use their embryos.
Twenty per cent declared that they were likely to leave leftover embryos
frozen 'forever'.
Researchers presented four
'disposition options'; thawing and discarding, reproductive donation,
indefinite freezing and donation for research. The majority found each
option unacceptable except donation for research; about 66 per cent of
respondents said that they would be likely to donate the embryos for
research, but that donation for that purpose was not available in all
clinics. A ban on federal funding for research involving human embryos
prevents many patients choosing this option.
More than half of patients
said that they were 'very unlikely' to donate 'spare' embryos to another
couple, citing reasons such as not wanting someone else bringing up their
children. Lyerly believes this contradicts the conventional wisdom that
'if you respect or care about an embryo, you would want it to become a
child' noting also that 'patients feel responsible for the care of the
children resulting from their embryos'.
Elizabeth Ginsburg, medical
director of the IVF clinic at Boston's Brigham and Women's Hospital
remarked that patients have asked for their embryos once they themselves
have decided not to use them. Small numbers of respondents in Lyerly's
study suggested solutions which were not widely offered, such as holding a
small ceremony whilst the embryos were thawed and disposed of, or placing
them in the woman's body at a point in her cycle when she would be
unlikely to conceive, thus letting them die naturally.
Anne Lyerly co-authored an
earlier study in 2007 which questioned how many fertility patients would
support donating their 'spare' embryos to embryonic stem (ES) cell
research, rather than to general medical research; a 60 per cent majority
were in support of this option compared to a 22 per cent group who would
prefer to discard them or donate them to other couples for adoption.
Despite this support, a removal of the ban to use federal funding for
human cell research was vetoed on the same day as Lyerly's results were
published.
Assisted
reproduction associated with elevated risk of birth defects
Lorna Stewart
Progress Educational Trust
24 November 2008
[BioNews, London]
A study published last week
in the journal Human Reproduction found an elevated risk of birth defects
amongst babies conceived through assisted reproductive techniques,
including IVF. The research, headed by Dr Jennita Reefhuis of the US
Centre for Disease Control and Prevention, used data from the National
Birth Defects Prevention Study to compare the health of babies born to
women who had used the techniques with infants born to women who had
conceived naturally.
Dr Reefhuis and colleagues
found that babies conceived using assisted reproductive techniques are
between two and four times more likely to have certain birth defects than
those who were conceived naturally. They are twice as likely to be born
with a cleft lip, four times as likely to have abnormalities of the
oesophagus or rectum, and two to three times as likely to have cardiac
defects. The researchers point out, however, that even with the increased
risks birth defects are still uncommon in these babies.
All the births included in
the study were single births, though multiple births are relatively common
in assisted reproductive techniques. Multiple births in general are known
to be at higher risk of birth defects, and this is one of the reasons that
techniques such as IVF have previously been thought to be associated with
a higher incidence of birth defects. This study also corrected for other
factors such as the age of the mother, folic acid use and alcohol intake.
The researchers are
explicit in their report that they do not know the cause of the elevated
risks. 'Our findings could have been because of underlying infertility,
small (sample) numbers or chance,' they said. Dr James Grifo, director of
the fertility clinic at New York University Medical Center, US, agrees. He
feels that due to the small sample size (281 assisted reproduction babies,
14,095 babies conceived naturally) more research is needed to confirm the
findings. He also said that if the association with birth defects was
real, the underlying cause was more likely related to the patients'
infertility than to the treatments they had undergone.
'Any couple who is
considering these treatments wants to be aware of all the pros and cons of
the treatment,' Dr Reefhuis said, adding 'I think it's important for
couples to be aware that there may be some increased risk for birth
defects as well.' Professor Michael Chapman, a senior fertility specialist
with IVF Australia, said 'There's no question that the evidence shows a
slight increase, and responsible IVF doctors are saying that to their
patients. But if your only way forward is IVF, then an increase in risk
from one in 100 to two in 100 for most people is an acceptable risk.'
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Overweight
women more likely to miscarry healthy babies
Rebecca Robey
Progress Educational Trust
17 November 2008
[BioNews, London]
Overweight women are at
greater risk of miscarrying a genetically normal baby in the early stages
of pregnancy than women who maintain a healthy weight, according to a new
study by scientists at the Stanford University School of Medicine in
California, US. The researchers, presenting at the annual American Society
for Reproductive Medicine (ASRM) conference, suggested that this indicates
that a mother's weight can affect the outcome of an otherwise healthy
pregnancy.
The UK's National Health
Service (NHS) estimates that around a quarter of all pregnancies in the UK
end in miscarriage. The majority of these occur in the first 12 weeks of
pregnancy, but can occur up to 24 weeks. The cause of miscarriage is not
always known, but it is thought that between 50 and 70 per cent occur as a
result of chromosomal abnormalities (genetic defects) in the fetus. The
California researchers tested DNA from 204 fetuses miscarried in the first
eight weeks of pregnancy. They compared the rate of chromosomal
abnormalities in the fetuses from women with a normal body mass index
(BMI) with the rate of abnormalities in fetuses from women with a BMI that
classified them as overweight or obese. They found that 53 per cent of
babies lost by overweight women had no chromosomal abnormalities compared
to just 37 per cent of babies lost by women of a more healthy BMI.
Dr Inna Landres, who led
the research team, said that these findings indicate that 'obesity
predisposes women to miscarry normal babies.' The reason for this is not
yet understood, but Dr Landres suggested that one explanation could be
altered levels of hormones such as oestrogen and androgens seen in
overweight women. She emphasised: 'It's important to identify elevated BMI
as a risk factor for miscarriage and counsel those women who are affected
on the importance of lifestyle modification.'
An individual's BMI is
calculated by dividing their weight in kilograms by their height in metres
squared. A BMI of 18 to 25 is considered normal, whilst over 25 is classed
as overweight and over 30 as obese. All the women in the current study
were attending an academic centre for fertility counselling and had their
BMI calculated before conception.
Dr Mark Hamilton, chairman
of the British Fertility Society (BFS), said: 'It is recognised that women
who are overweight are at a greater risk of miscarriage. It has not been
defined if that risk is related to genetic problems for the embryos or the
obesity itself is linked to implantation mechanisms. This study will aid
our understanding of the known association with being overweight and
reproductive loss.'
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Slow-frozen
embryos seem to produce healthier babies in IVF [Correction]
Alison Cranage
Progress Educational Trust
17 November 2008
[BioNews, London]
Three new independent
studies have provided further evidence that embryos stored using
slow-freezing techniques may be better than fresh for IVF. The studies
were presented at the American Society for Reproductive Medicine
conference in San Francisco, US, last week. The studies indicate that
using frozen embryos rather than fresh embryos reduces the risk of
stillbirth and premature delivery.
It is unclear why this is
the case; there are several theories. Some experts have suggested that
when fresh embryos are used women may still be suffering from the effects
of the powerful drugs that are used to stimulate the ovaries, temporarily
disrupting any IVF attempt shortly afterwards. Dr Allan Pacey, from the
University of Sheffield and secretary of the British Fertility Society (BFS),
said: 'These findings are really quite interesting. It kind of defies
logic to a certain extent, because the stimulation drugs and anaesthetics
that are used in egg collection have worn off by the time fresh embryo
transfers are done. It seems to be an issue with the formation of the
placenta, but how it has an effect isn't known.' Another theory is that
only the 'best' embryos surviving the freezing and thawing processes,
which can damage the embryo either as the result of ice crystals forming
or of an increase in the concentration of solutes as progressively more
ice is formed.
The three large,
independent studies took place in Finland, Australia and the US. The
Finnish study, found that babies born from fresh embryos were 35 per cent
more likely to be premature and 64 per cent more likely to have a low
birth weight when compared to those born from frozen embryos. The research
that took place in Melbourne, Australia, showed that 11 per cent of babies
born from fresh embryos had a low birth weight, compared to 6.5 per cent
of those born from frozen embryos. They also found that 12.3 per cent of
babies born from fresh embryos were premature, compared with 9.4 per cent
of those born from frozen embryos. Also, 1.9 per cent of babies from fresh
embryos died a few days after birth, compared to 1.2 per cent from frozen
embryos. Similar findings were reported in June this year from a Danish
study.
Typical IVF treatment
involves stimulating a woman's ovaries with hormones to produce eggs which
are then collected and fertilised in the laboratory, with one or two
embryos being transplanted into the womb two days later. The remaining
embryos can be slow-frozen and then stored, to be used later if the
initial cycle fails.
The new data may provide a
dilemma for IVF clinics, as although frozen embryos seem to result in a
healthier pregnancy, the pregnancy rate is less successful. Commenting on
this, Dr Pacey said: 'Frozen embryo transfers are not as successful as
fresh ones in terms of getting a pregnancy. So it may be that we have to
balance the health of children against chance of success.'
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Woman gives
birth to twins conceived with 13 year-old sperm
Sarah Guy
Progress Educational Trust
17 November 2008
[BioNews, London]
A woman in Taiwan has used
the frozen sperm of her cancer-survivor husband to conceive and give birth
to healthy twins. The woman's husband, surnamed Chen, was diagnosed with
testicular cancer whilst studying at university aged 23. He cryogenically
preserved samples of his sperm at Taipei's Medical University Hospital
sperm bank, before undergoing chemotherapy which would potentially leave
him infertile. Chen overcame the cancer but ceased to produce sperm. After
getting married earlier this year, 36 year-old Chen and his wife decided
they wanted their own child and so asked doctors to assist them using
Chen's preserved sperm.
'The birth is a record in
Taiwan' said Tseng Chi-jui, head of the Centre for Reproductive Medicine
and Sciences at Taipei Medical University's College of Medicine. 'Never
before has a case involving such a long period of time between the
freezing of male sperm and procreation been reported in Taiwan'.
Tseng used IVF to extract
four eggs to be fertilised with Chen's unfrozen sperm and only two of the
four re-implanted successfully into his wife's womb. As sperm tend to lose
motility (the number of sperm active or moving) after defrosting, the
fertility expert used intracytoplasmic sperm injection (ICSI) technology
to ensure precise fertilisation with Mrs Chen's eggs.
Improvements in cryogenics
and assisted reproductive technologies have the potential to assist those
with serious illnesses facing treatment which may render them infertile,
Tseng said. Sperm cryopreservation enables such patients to 'save' their
sperm for future procreation.
Mrs Chen gave birth to
healthy twin boys at 37 weeks, one weighing four pounds six ounces, and
the other weighing six pounds.
Earlier this year, a UK
couple conceived a second baby using sperm frozen 19 years ago at St
Mary's Hospital in Manchester. Emmanuel and Zoe Iyoha received IVF
treatment using sperm preserved on Mr Iyoha's behalf in 1989, before he
underwent successful treatment for cancer. In 2004, doctors at St Mary's
hospital reported the birth of baby conceived using sperm that had been
frozen for 21 years, believed to be the longest reported storage period
for sperm successfully used for treatment.
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Screening
embryos before IVF improves success rate
Lorna Stewart
Progress Educational Trust
17 November 2008
[BioNews, London]
The first trial of a
procedure which selects IVF embryos with the best chance of developing
into healthy babies was presented last week at the American Society for
Reproductive Medicine conference in San Francisco. Dr Dagan Wells and
colleagues at Oxford University, UK screened embryos for 23 women before
implantation and showed a much improved success rate of IVF; 18 out of the
23 women have either already given birth or have passed the point in
pregnancy at which miscarriages typically occur.
The embryo quality test,
which uses a technique called comparative genomic hybridisation (CGH),
means embryos' chromosomes can be more comprehensively screened for
abnormalities. This is not the first pre-implantation genetic test to be
developed but Dr Wells' test screens embryos at a later stage of pregnancy
(when the embryo is five days old and has more than 100 cells). This means
that every chromosome pair in the embryo can be examined and, since more
cells can be removed for analysis, it yields more accurate results.
The 78 per cent success
rate reported by Dr Wells and colleagues is significantly better than the
rate usually achieved (60 per cent) in a patient group like this who have
all had unsuccessful IVF treatment previously and have an average age of
37. Following CGH screening, the implantation rate for each individual
embryo is 62 per cent - the normal rate is 28 per cent. Dr Wells said,
'The pregnancy rates we've got so far are absolutely phenomenal. The
probability that one embryo leads to a pregnancy is doubled. That means
that you've got a much better chance of a pregnancy if you do a single
embryo transfer.'
Dr Wells and colleagues are
now ready to begin a larger scale trial in the UK and have applied for
permission from the Human Fertilisation and Embryology Authority (HFEA,
the fertility watchdog) to offer the test to patients at the Oxford
Fertility Unit. It is anticipated that the test would add around £2000 to
the present £4000 cost of IVF treatment.
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