Stages of pre-implantation genetic diagnosis


Preimplantation genetic diagnosis

The pre-implantation genetic diagnosis treatment cycle is made up of eight stages.

  • Stage one – stimulation of the ovaries

    Your ovaries are stimulated with hormones, given to you as an injection under the skin, on the thigh or tummy. 

    In most cases we use what we call a “short antagonist” protocol. This means you will take a combination of two drugs for 10-14 days to prepare your ovaries for egg collection.

    We will explain the potential side-effects of these injections and monitor your response using internal scans. The first scan is usually done between eight and eleven days after starting the injections.

  • Stage two – collection of eggs from the ovaries

    You are deeply sedated and monitored throughout the egg collection procedure, which usually takes about 20 minutes. Using an ultrasound probe as a guide, a fine needle is passed inside the vagina and through the vaginal wall into each follicle, until we have emptied all the follicles in one ovary. The needle is then removed and the procedure is repeated in the other ovary.

  • Stage three – insemination/injection of sperm

    The man’s semen sample is prepared by separating the normal and active sperm from the ejaculated fluid. Fertilisation during pre-implantation genetic diagnosis (PGD) treatment will be done either by:

    • injecting a single sperm into the centre of each egg to achieve fertilisation
    • in vitro fertilisation (IVF) where sperm and eggs are placed together in a culture dish to allow fertilisation to occur in the laboratory.
  • Stage four – fertilisation

    The morning after injection/insemination of the sperm, the embryologist carefully examines each egg to see if fertilisation has occurred. We will then call you to tell you how many eggs have fertilised.

    Rarely, about one in 100 times, none of the eggs fertilise and there are no embryos so the PGD cycle cannot continue. This is obviously very disappointing. We will offer you the earliest available appointment to see a PGD team doctor and an appointment to see one of our counsellors.

  • Stage five – embryo biopsy

    Eggs that have fertilised are called embryos. As embryos develop, their cells divide. When embryos have grown for 5-6 days and form blastocysts, the embryo biopsy procedure can take place. We call this trophectoderm biopsy and it is used in most PGD cycles. There is a chance that none of the embryos will reach the stage of being suitable to be biopsied.

    The cells are then transferred to the scientists to start the DNA or chromosome testing. All the embryos are immediately frozen and will stay in storage until the genetic results are ready.

  • Stage six – embryo testing

    The types of tests we perform on the embryos will depend upon the reason behind you having pre-implantation genetic diagnosis.

    If you are referred to us you will be sent leaflets about these tests.

  • Stage seven – embryo transfer

    Most couples going through pre-implantation genetic diagnosis (PGD) will have a frozen embryo transfer. Once the results of embryo testing are known the PGD nurses will plan the date of embryo transfer.

    Our policy is to transfer just one embryo in most cases. This does not make the chance of success any less than transferring two embryos, but is safer for you and the baby. It means that any additional unaffected embryos, can stay frozen for future use, if required.

    You will know if the treatment has been successful 10-12 days after embryo transfer.

  • Stage eight – pregnancy test

    All women should perform a pregnancy test 12 days after the embryo transfer, even if they bleed before this time. This is essential because some patients who have bleeding could have an ectopic pregnancy, which is an uncommon, but potentially serious, complication. We will give you a pregnancy test kit and ask you to phone the unit to give us the result.

    A positive pregnancy test means that an embryo has implanted, but we will not be able to see this on a scan until you are about six weeks pregnant, four weeks after embryo transfer. Sadly, we sometimes diagnose miscarriages and ectopic pregnancies at this stage.

    A negative pregnancy test means that the treatment has been unsuccessful. If you have not already started bleeding, a period will come in the next few days. A follow up appointment will be made for you to see one of the doctors to discuss plans for future treatment.

    You might also find it helpful to see one of our fertility counsellors or you can speak with your PGD genetic counsellor who will know the outcome.