Humans spend a lot of time and energy choosing their partner. A new study by researchers from Stockholm University and 91ֱ�� University NHS Foundation Trust (MFT) shows that choosing your partner continues even after sex – human eggs can “choose” sperm.

“Human eggs release chemicals called chemoattractants that attract sperm to unfertilised eggs. We wanted to know if eggs use these chemical signals to pick which sperm they attract,” said John Fitzpatrick, an Associate Professor at Stockholm University.

The researchers examined how sperm respond to follicular fluid, which surrounds eggs and contains sperm chemoattractants. The researchers wanted to find out if follicular fluids from different females attracted sperm from some males more than others.

Microscopic mate choice

“Follicular fluid from one female was better at attracting sperm from one male, while follicular fluid from another female was better at attracting sperm from a different male,” said Professor Fitzpatrick.

“This shows that interactions between human eggs and sperm depend on the specific identity of the women and men involved.”

The egg does not always agree with the women’s choice of partner. The researchers found that eggs did not always attract more sperm from their partner compared to sperm from another male.

Is this egg or sperm choice? Professor Fitzpatrick explained that sperm have only one job – to fertilise eggs – so it doesn’t make sense for them to be choosy. Eggs on the other hand can benefit by picking high quality or genetically compatible sperm.

“The idea that eggs are choosing sperm is really novel in human fertility,” said , the Scientific Director of the Department of Reproductive Medicine at Saint Marys’ Hospital, which is part of MFT, and the senior author of this study.

The University of Manchester Honorary Professor added: “Research on the way eggs and sperm interact will advance fertility treatments and may eventually help us understand some of the currently ‘unexplained’ causes of infertility in couples.

“I’d like to thank every person who took part in this study and contributed to these findings, which may benefit couples struggling with infertility in future.”

The article Chemical signals from eggs facilitate cryptic female choice in humans is published in the scientific journal Proceedings of the Royal Society B.

A new study led by University of Manchester scientists has revealed that babies born by In Vitro Fertilisation at St Mary’s Hospital in 91ֱ�� have increased in birthweight by nearly 200g over the past 25 years.

The research - published in the journal Human Reproduction – highlights a possible change between babies born in the earlier years of the technique and today’s IVF infants.

Existing studies based on children born in the first 20 or 30 years of IVF treatment show that they tend to have a low birthweight, which studies of non-IVF children have shown may carry a possible risk of health problems in later adult life.

A November 2018 paper from the team led by Professor Daniel Brison showed for the first time that IVF babies also show postnatal catchup growth after low birthweight, which may add to the risk.

Their study showed that freezing embryos seems to offset the risk, resulting in babies with more normal birthweight and early growth.

Most IVF embryos are implanted fresh, though techniques have changed markedly since its earliest days.

However, the latest study from the team shows that as well as increases in the success rate of IVF, birthweights have also increased, by an average of nearly 180g over 25 years - or just under10% - irrespective of which method of IVF is used.

The team cannot identify why birthrates are higher now, but argue the increase has probably been a gradual increase over time.

Professor Brison said: “Although it is too soon to know if there will be any long term health impact on earlier IVF children, such effects would in any case be small.

“But we do feel it is important to continue to monitor the health of all IVF children and alter IVF practices to make the treatments as safe as possible.

“Our research further suggests that the newest generation of IVF children may be at lower risk.

“We believe that is likely to be because IVF techniques have changed markedly over the past 25 years –though it’s hard to pin point exactly which changes might be important.”

The current research is a retrospective study of nearly 3000 singleton live births at St Mary’s Hospital 91ֱ��.

The November paper is a national register-based study linking the HFEA register of all IVF children to maternity databases in Scotland with records of birthweight and early child growth for 5000 IVF children.

Both studies were funded by EU science grants.

“The impact of IVF on birthweight from 1991 to 2015: a cross-sectional study” is published in Human Reproduction

“The growth of assisted reproductive treatment-conceived children from birth to 5 years: a national cohort study” is published in BMC Medicine

A study has linked babies conceived through a type of IVF to lower birth weight followed by increased growth after birth.

The University of Manchester led study of 5,200 IVF children found that singleton babies conceived from fresh embryo transfers - used in two thirds of all IVF - are associated with lower birth weights, head circumference and length, but then grow more quickly, catching up to naturally conceived children by school age.

The team are also monitoring birth weight in IVF babies over a 25-year period, and initial results show that weight seems to be increasing. It may be that recent improvements in IVF technology are responsible, though it’s too early to know for sure, say the team.

Babies conceived from frozen embryo transfers – used in about one third of IVF- have greater weight, head circumference and length at birth and show similar growth to naturally conceived children.

“Though the effects are small, they do justify considering using the safest form of IVF treatment where possible, and continuing to monitor the long-term health of these children,” said reproductive biologist Professor Daniel Brison who led the study.

“Overall IVF babies are just as likely to be born healthy as any other, and the lifestyle choices they make in later life will far outweigh any small effect of low birthweight and altered growth,” explained Professor Brison.

Using Scottish data, it is the first large-scale study of early growth in IVF children from birth to school age anywhere in the world, and only the second study of health in UK IVF children using the Human Fertilisation and Embryology Authority register of IVF treatments.

The European Union funded study, which involved researchers from the Universities of Manchester and Southampton, is published today in BMC Medicine.

Among the headline findings are:

• The birthweight of babies born from fresh embryo transfer cycles is on average 93·7g less than naturally conceived babies.
• Babies born from frozen embryo transfers are on average 57·5g heavier.
• Fresh embryo babies grew faster from birth by on average 7·2g/week but remained lighter by 171g, at 6-8 weeks, than normally conceived babies and 133g smaller than frozen embryo transfer babies; who were similar to normally conceived babies.
• By school entry (4-7 years), weight, length and BMI in boys and girls conceived by fresh and frozen embryo transfer were similar to those in naturally conceived children.

Professor Brison said: “We don’t yet know why fetal and child growth for children conceived through this form of fertility treatment is affected.

“Babies born from IVF appear largely healthy, though the oldest of them, Louise Brown, is still only 40 so we feel there is a duty to monitor this cohort of children for diseases which show up only in later life.

“The impact of fresh embryos transfer on birth weight is after all nearly as great as that of maternal smoking in pregnancy. One possible explanation, say the team, is that fetal growth is restricted with fresh embryo transfer because of impaired placental function associated with dysregulated maternal hormones. Freezing embryos, they argue, may also help to preserve them to establish pregnancy later on when the mother’s body has recovered from IVF.

“But IVF children need not be alarmed: the greatest risk from IVF is multiple pregnancy, and the IVF field and government regulator (HFEA) have worked together to improve this greatly over the last 5-10 years.”

“” is published in BMC Medicine.

The world's first “test tube” baby was conceived by IVF in Greater 91ֱ��, at Dr Kershaw's Hospital in Royton. Louise Brown was born at Oldham General Hospital forty years ago on 25 July 1978.

The work at Dr Kershaws was carried out by Patrick Steptoe, Jean Purdy and Bob Edwards. Professor Edwards received the Nobel Prize in Physiology and Medicine in 2010.

Reproductive biology experts Professors John Aplin and Daniel Brison, and others will be marking the fortieth anniversary of IVF and the unique role 91ֱ�� played in it at events on 24 and 25 July.

Professor Brison, from The University of Manchester and 91ֱ�� University NHS Foundation Trust said: “IVF has changed the world, thanks to the work of Steptoe, Purdy and Bob Edwards at Dr Kershaws.

“The first NHS-funded IVF service was also established in 1983 at St Marys Hospital here in 91ֱ��. Since then, IVF babies now total over 6 million and make up more than 2% of all UK births.

“Living in Oldham myself, I know Dr Kershaw ‘s well and believe it’s time we focus attention on the neglected role this hospital played as the world’s first successful IVF clinic.”

Professor Aplin, from The University of Manchester, said: “Greater 91ֱ�� has played a hugely important role in the history of IVF, going back to Walter Heape, who first carried out embryo transfer in rabbits at his home in Prestwich in 1890.

“But IVF has also given birth to the field of human embryonic stem cell biology and has led to major advances in reproductive biology. Ground breaking research in 91ֱ�� on human embryo development and implantation has continued to contribute to the advancement of IVF science.”

Dr Raj Mathur, a fertility expert and Clinical Lead of the 91ֱ�� University Foundation Trust IVF Service and Professors Brison and Aplin have organised an international  with the Society for Reproduction and Fertility on the history and future of IVF treatment on 25 July. It will be preceded by a free public lecture on the July 24 on the role of Greater 91ֱ�� in the early history of IVF. Professor Roger Gosden, a world renowned reproductive biologist and the official biographer of Bob Edwards will deliver a public lecture at 91ֱ�� Royal Infirmary entitled “Let there be life”. Tickets are available