IVF and gender selection options
IVF gender selection is an incredibly controversial topic, and one which raises many ethical questions, depending on the reason selection is being sought. In this webinar, Dr Murat Onal, Medical Director of Gynolife IVF centre in Nicosia, Cyprus, discusses why parents may want to carry out sex selection testing, and if so, what exactly it entails.
There are two main reasons why potential parents-to-be may decide to go ahead with gender selection; genetical reasons, or family balancing. It is currently illegal, in some countries, to undergo gender determining procedures solely for parental preference, where there are no genetic or chromosomal concerns.
To fully understand why gender selection may play an important role, when researching genetic health, it is important to look at the chromosomes within humans, specifically in relation to the differences between the sexes.
Men and women basically have the same set of around 20,000 genes, with the only physical difference, in the genetic make-up, being the sex chromosome; the Y chromosome is only present in males and although both sexes have the X chromosome, females have two (XX), whereas males only have one, to accompany their Y (XY). During fertilisation, an XX oocyte (egg) is produced and fertilised by either an X or Y sperm. These chromosomes then fuse together to create either an XX (girl) or XY (boy) baby.
Chromosomal linked disorders can be carried by either parent and depending on the anomaly, have the capacity to cause defects in birth, as well as embryo implantation issues. In these cases, testing may be advised in order to eliminate any potential risks, to the unborn child, and to increase the chances of achieving a viable, healthy, pregnancy. As genetic problems are known to lie within the chromosomes whether a disorder will be passed on to any offspring, is dependent on both who the carrier is (mother or father) and the gender of the child, as chromosomal irregularities can be gender specific in their continuation down a family line.
Whilst it might be advantageous to offer genetic selection in some situations in order to safeguard the pregnancy or health of the child is it actually possible to tell the sex at embryo stage, or even determine this beforehand, and is testing safe? Dr Onal outlines the different methods and procedures, his clinic uses, and answers some of the main questions, surrounding the issue.
IVF gender selection options
At Gynolife IVF centre, two main categories, of gender determination, are used; sperm selection and/or PGS (preimplantation genetic screening).
- Sperm selection is the least invasive procedure and takes place before fertilisation, meaning IVF does not have to be the only form of assisted conception considered, by the patients. The sperm can be checked in two ways; either by using specialised lasers, which distinguish and identify the X and Y cells in seminal fluid or by separating the X and Y sperm using centrifugation. However, whilst these methods are simpler and can increase the chances of gender selection, Dr Onal advises that with only a 60-80% accuracy rate, depending on the procedure used, there is room for error.
- Within IVF, the use of PGS (preimplantation genetic screening) is increasing, embryologists are now able to analyse the chromosomes, in embryos, enabling them to transfer only those which have the best potential for implantation. As gender determination is chromosomal, PGS is a procedure that can also be used for this reason.
PGS is only available as an IVF treatment as the screening takes place using cells removed from an embryo. These cells are then tested for any anomalies and/or gender. Dr Onal advises that embryo biopsies can delay cycles of IVF, although, three-day, or blastomere, biopsies are possible, allowing for a fresh transfer to still take place. After 72 hours, it is expected that an embryo will contain between seven to eight cells, and in order to complete the screening, one to two, of these cells, are removed and examined. Tested embryos should then recover and continue with their development again. However, due to the invasive technique of the biopsy, Dr Onal warns that conducting PGS this early, may in fact have a negative effect on the embryo. He also cautions that a day three analysis may not always give embryologists the full picture of embryonic health; embryos can, and do, correct themselves, meaning an embryo on day three which appears aneuploid (abnormal), could potentially right itself, given additional time. Day three information may not always be accurate in the longer term.
Another PGS option, for gender and euploid (normal embryo) selection testing, is a trophectoderm biopsy which would usually, happen at blastocyst (day five) stage. With this technique only cells from the crust, or inner line, of the embryo are retrieved, allowing for a less harmful effect on any tested. This crust contains the main cells and enables the genetic lab to identify, and review, all the chromosome pairings with increased accuracy, as each sample tested includes more than just one or two cells, as per blastomere biopsies. Trophectoderm biopsies are, currently, the most common method of PGS used.
At the Gynolife clinic, Dr Onal says that gender recognition is 99% accurate, from both the blastomere and trophectoderm biopsies.
All of the techniques, mentioned in this webinar, can be used with regard to family balancing too, however, Dr Onal stresses that there are ethical considerations in gender checking, for this reason alone, and as a result, this is only, legally, available in a few countries, within Europe.