Monitoring egg development
In a normal female cycle, only one follicle develops on alternative ovaries to allow one egg to ovulate. If this egg does not fertilise then this will result in a menstrual period. During an IVF cycle, drugs are given to stimulate both the ovaries allowing more follicles to develop and several eggs to be collected. The dose of drugs is tailored to allow sufficient follicles to grow but without stimulating the ovary so much that there is a risk of OHSS.
The size of the follicles is monitored regularly via ultrasound scans and the dose of drug is reviewed after every scan.Once a sufficient number of optimum sized follicles have developed a HCG (human chrorionic gonadotrophin) injection is given. This will ensure the final maturation of the eggs and will allow the release of eggs from the follicle. This drug needs to be carefully timed and is usually between 34 and 36 hours before the egg collection.
The egg collection is minor surgical procedure and is performed under a light general anaesthetic or intravenous sedation.It is performed using a needle guided by ultrasound. The needle is passed through the vaginal wall and into the ovary. Each follicle is then punctured and the follicle fluid suctioned out in to a test tube. Most women remember little about the egg collection afterwards due to the effect of the anaesthetic drugs.
The procedure time can range from 10 to 20 minutes depending on how many follicles there are in each ovary. Not every follicle contains an egg. We usually obtain eggs from 70-80% of good sized follicles.
Once the egg collection is completed, the patient will rest for several hours on the ward before being allowed home. It is not permitted to drive after anaesthetic or sedation.
Side effects and complications of egg collection
It is common to have some cramp-like pain (like period pain) for approx 24-48 hours after egg collection. It is also common to pass a small amount of blood, which comes from the site of needle puncture.
Egg collection carries with it a very small risk of infection and of puncturing a blood vessel or loop of the bowel. Such complications are extremely rare but, should you feel particularly unwell, or experience severe, sharp pain you should ring the unit immediately. If the unit is closed, you should use the emergency bleep number or go to the Accident and Emergency Department of your nearest NHS Hospital where one of our doctors can be contacted.
Following the egg collection, the embryologist will confirm the numbers of eggs retrieved and the man will be asked to produce a sperm sample. This is done by masturbation as for the pre treatment semen analysis. In order to ensure a good sample on that day he will have been asked to refrain from intercourse and masturbation for 3-4 days before then.
Occasionally, it is necessary to ask for more than one sample. Some men find it difficult to produce a sample on what is a stressful day in a strange place. If there are concerns then the sample can be frozen as a back up prior to the treatment.
What happens in the laboratory?
Insemination/injection of sperm
The embryologists will prepare the sperm sample by separating the normal moving sperm from the seminal fluid. In an IVF cycle, approx. 100,000 sperm are added to each egg on the day of egg collection. In an ICSI cycle, the eggs are stripped of their outer coating and a single sperm is injected into each egg.
The next morning the embryologist will examine the eggs under a microscope looking for the characteristic changes that occur if the egg have fertilised. We expect about 60% fertilisation rate at IVF, 70% with ICSI. The embryologist will telephone you later in the morning to check how you are, to tell you how many eggs have fertilised and arrange an appointment for embryo transfer, usually two to three days after egg collection. Very occasionally none of the eggs fertilise.
This can happen in either an IVF or ICSI cycle, and may occur even if the eggs and sperm appear normal. This is obviously very disappointing and we will offer you an appointment to return to the clinic to discuss both this cycle and your further treatment options. Failure of fertilisation is usually due to poor sperm quality, but may occasionally be due to an egg problem.
Eggs that have fertilised are called embryos. As embryos develop, their cells divide. Two days after fertilisation the embryo should have two to four cells; three days after fertilisation it should have six to eight.
The cells divide very rapidly after this to become a ball of cells (a morula) by day 4, and a blastocyst with differentiation of the cells in to a trophectoderm (which will eventually become the placenta) and inner cell mass (which will eventually become the foetus) by Day 5.
Embryos are usually transferred between two and six days following the egg collection.
Embryo transfer is an outpatient procedure and should take about half an hour. It is best to have a comfortably full bladder for embryo transfer. The embryos are loaded into a soft catheter (hollow tube) and this is passed through the neck of the womb, into the womb itself.
We may check the position of the catheter by an ultrasound scan through your tummy. Once we are sure the catheter is correctly positioned, the embryos are gently injected and the catheter withdrawn. The embryologist will check the catheter to make sure that all the embryos have been transferred.
The procedure is usually quick and painless (It is similar to a smear test) and you may go home after a short rest. You may empty your bladder straight afterwards without any risk of losing the embryos.
How many embryos?
Current guidelines from the HFEA allow us to transfer a maximum of two embryos to a woman under the age of 40, a maximum of 3 if she is over 40.
However transferring more than 1 embryo increases the risk of multiple pregnancy, which carries a significantly higher risk of complications including miscarriage and premature birth, and new legislation also obliges clinics to transfer 1 embryo only in selected patients in whom the risk of multiple pregnancy is highest. This will be discussed fully with each individual couple.