Human eight-cell embryo for IVF selection

Doing without sex

Will there come a day when reproduction is entirely separated from the human body?

Pregnancy and childbirth are major challenges to the female body. An expectant mother has to provide nutrition and a safe environment for her growing baby, and childbirth thrusts a vulnerable baby into a harsh outside world. Until recently the death of a mother or infant during or immediately after birth was common in the West, and remains so in many parts of the developing world.

In vitro fertilisation

The first step in producing a new individual, fertilisation, can take place outside the body. In 1978 Louise Brown became the world’s first ‘test-tube baby’, a landmark in medicine. This procedure, in vitro fertilisation (IVF), has now become routine. In 2012 the number of children born by IVF reached five million.

In IVF, women are given fertility-boosting hormones to encourage their ovaries to produce more eggs. Once collected, the eggs are mixed with sperm in the lab. If the egg is fertilised, the resulting embryo is allowed to develop for a few days and is then implanted in the mother’s womb.

IVF is used when would-be parents have difficulty conceiving a child – for instance when a woman’s eggs do not travel through her reproductive system properly, or a when a man has a low sperm count. If a man has immotile sperm, which cannot swim to an egg, sperm can be directly injected into the egg – a procedure known as intracytoplasmic sperm injection (ICSI).

Success rates vary with age – for women under 35, the success rate in the UK is around 32 per cent. This drops quickly to 28 per cent between 35 and 37, falling to 5 per cent by the age of 43. Although it can be a difficult experience, both physically and emotionally, IVF provides an alternative option for couples who are having difficulties conceiving.

The artificial womb

Creating an embryo may be relatively easy, but nurturing it to the point of independent existence certainly is not. The arrival of artificial wombs periodically makes headlines, but they remain science fiction for now – at least for human babies. The medical need for these arises from the desire to save developing fetuses that might otherwise die – for example when an expectant mother’s womb is damaged, such as in a road traffic accident.

A second important focus is the survival of premature babies. Great strides have been made in this area, and infants born so prematurely that they would have died in previous eras can often be saved. But there is a limit, and even those that do survive sometimes suffer brain damage or other harm.

The growth of a new baby in the womb is highly complex, and the placenta plays a key role in providing the right nutrients, protecting the fetus from harmful substances and removing waste products. Recreating these functions artificially is a huge challenge.

One approach is to try to grow womb-like structures in culture. A group at Cornell University in the USA has had some success in growing cells from the lining of a human uterus, and has used tissue engineering to mould them into a womb shape. The group has also grown mouse embryos nearly to term in an artificial womb, though the newborn mice did not survive.

In a 2012 study researchers made an artificial uterus from acrylic and used it to grow shark embryos taken from pregnant female sharks. After ‘birth’ these shark pups seemed to be just as healthy as ordinary shark pups.

Medical need and social application

Dolls coming off a factory line, labelled male and female

Dolls coming off a factory line, labelled male and female.

Credit:

Catherine Riley/Wellcome Images

This kind of work inevitably seems to lead people to imagine ‘baby factories’ growing new infants to order.

But it is worth remembering that the primary purpose of such research is to save babies’ lives or to help the infertile. There may one day be wider applications of these technologies, but for the foreseeable future these are likely to be difficult procedures to carry out and used only when absolutely necessary.

Take preimplantation genetic diagnosis (PGD). This involves taking a cell from an early human embryo during IVF and carrying out genetic tests on it. Through this technique parents at risk of having a boy with an X-linked genetic disease can have a female embryo implanted, or parents from families with inherited disorders can implant an embryo without a disease gene.

There are fears that this could be used to create ‘designer babies’, where parents select embryos with particular features. In reality, the links between genes and particular features, such as intelligence, are so complicated that this is unlikely to be a realistic scenario. Plus, the procedures themselves are difficult and not undertaken lightly. Finally, in the UK at least, reproductive technologies are highly regulated (by the Human Fertilisation and Embryology Authority), so socially undesirable applications would face many hurdles.

Lead image:

A human eight cell embryo, which is considered to be grade one, meaning it is of sufficient quality to be used for IVF.

K Hardy/Wellcome Images CC BY NC ND

References

Further reading

About this resource

This resource was first published in ‘Sex and Gender’ in January 2006 and reviewed and updated in October 2014.

Topics:
Cell biology, Genetics and genomics, History, Biotechnology and engineering
Issue:
Sex and Gender
Education levels:
16–19, Continuing professional development