It has been nearly 44 years since the first successful in vitro fertilization (IVF) procedure was performed 1978 in Lancashire, England. Since then, more than 8 million children They are born all over the world for assisted reproductive technologies, such as artificial insemination.
But despite the increasing use, the success rate of IVF is still relatively low, at around 30%. There may be a number of reasons for this. In our recent paper, we argue that this low rate is partly due to many Unfavorable genetic changes that we carry in our DNA.
Genetic changes occur when mutations in our genes replace, insert or delete parts of our DNA. More of these mutations It now occurs in humans because we have children at a later age. As we get older, more Mutations are more likely to accumulate This means that older parents are more likely to pass on genetic mutations to their children than younger parents. Mutations may also occur due to environmental factors (eg, ultraviolet rays in sunlight), or lifestyle choices (eg, smoking).
All genetic changes that we inherit or develop throughout our lives make up what is known as a genetic load. This genetic load can affect our ability to reproduce. and as our study It is suggested that this may also affect our ability to reproduce via methods such as artificial insemination.
Genetics and pregnancy
Gene mutations make evolution possible. They provide a new material for natural selection that allows species to adapt and evolve. While most of these mutations have no effect, some do a little malicious. These harmful mutations may cause diabetes or breast cancerfor example – or it may disrupt the healthy development of the fetus.
Human DNA carries more than 1000 harmful mutationsMost of it happened several generations ago. However, although it is harmful, it has not been removed (yet), because natural selection is a very slow process.
In addition to the large number of old mutations, new mutations also enter the society each generation. On average, each person acquires Nearly 70 new mutations during their lives. But since some of these mutations are harmful, they must be removed by natural selection, so that they are not passed on to offspring in the future. One of the most important times this happens is during a normal pregnancy.
When a baby conceives normally, the body has several mechanisms in place to remove some of these harmful mutations.
For example, the female reproductive system is designed in such a way that only the fittest sperm cells can reach the egg for fertilization. Although evidence is scarce, animal studies suggest that sperm that reach the fertilization site have better DNA quality and Likely to have fewer mutations.
Ripe eggs also undergo a kind of Quality Check during fertilization. This also helps remove some of the genetic burden. The implantation stage (where the fertilized embryo implants itself in the mother’s womb) is also important, as many severely affected embryos genetic abnormalities They tend to lose weight naturally during pregnancy.
However, IVF It bypasses some of these natural mechanisms. During IVF, multiple eggs are harvested from a woman’s ovaries and fertilized with sperm in a laboratory. After fertilization, the embryos are returned to the uterus. This reduces the chance of natural selection, which could make IVF less efficient at reducing genetic load. This may increase the possibility of harmful variants being passed from genes to the next generation.
Therefore, genetic load has two major effects on human reproduction. First, the genetic load of the parents affects their ability to successfully procreate. This is true for a natural pregnancy as well as for IVF. Second, by relaxing natural selection, IVF may allow more mutations to slip through the network. As such, it can slowly increase the genetic load in future generations. But there may be a solution.
The future of artificial insemination
Fertility rates have suffered an unprecedented decline in recent decades. In fact, his sperm count decreased by about 50 to 60% Between 1973 and 2011. It is unclear why this is, but if this trend continues, it could mean that more people are turning to IVF to get pregnant.
However, we still know surprisingly little about human reproduction and the selective processes that operate during normal pregnancy. We must understand natural pregnancy first if we are to improve assisted reproductive methods, including IVF. But recent technological advances in assisted reproductive technologies mean that we may soon be better able to address some of the genetic burden in humans. for example Sperm level selection In the process of IVF, it has been shown to improve the fitness of offspring in animal models. In particular, selection for long-lived sperm in zebrafish results in healthier offspring that live longer.
Advances in genomic technologies also have the potential to influence human evolution. Already, genomic data is being used effectively in clinical care, and the genetic underpinnings of Thousands of human diseases now known. Furthermore, changes to our environment and lifestyle affect genetic burden and human health. In most cases , These changes have a negative effect, making these technological advances more important than ever. As new progress is made, it will also be important to consider the potential consequences of using assisted reproductive techniques if this becomes the norm.