A blastocyst is an embryo which has developed into a multi-cellular mass five or six days after the sperm has fertilised the egg. It absorbs fluid and expands, consisting of a layer of outer cells which eventually become the placenta and a small number of inner cells which will form the fetus. When the blastocyst is fully developed and the zona pellucida has reduced to a very thin layer, it undergoes a series of repeated contractions and re-expansions, exerting a pressure on the zona pellucida which finally breaks and allows the blastocyst to ‘hatch’ through the ‘shell’, before implanting into the uterine lining.
In IVF and ICSI treatment, embryos may be transferred two or three days after fertilisation or, alternatively, at blastocyst stage, after two or three days’ additional culture in an embryology laboratory.
Is blastocyst transfer suitable for every patient having IVF or ICSI?
Blastocyst transfer may be suitable for the following patients:
- those who are advised for medical reasons to avoid a twin pregnancy
- those who would prefer to avoid a twin pregnancy for other reasons
- those who meet the criteria for a single embryo transfer according to the SET protocol
- those who have had negative results after earlier embryo transfers
Midland Fertility carefully assesses the possible benefits of blastocyst transfer for each patient before recommending it as part of any treatment plan.
What does treatment involve?
Following a first appointment, appropriate investigations, follow-up appointment, screening, matching and treatment planning, and possible counselling, a patient will begin IVF or ICSI treatment as recommended by the clinical and scientific teams at Midland Fertility.
- in advance of the egg collection, the patients will consent to the number of embryos to be transferred, according to the Midland Fertility embryo transfer policy
- members of the clinical and laboratory staff will discuss the possibility and any advantages of a blastocyst culture and transfer at this stage
- after egg collection and fertilisation, the embryos will be closely monitored to assess their suitability for developing to blastocyst stage before transfer. The final decision to extend the culture to the blastocyst stage is made three days after the egg collection. Laboratory staff then inform patients of the progress of their embryos and discuss the individualised advantages and disadvantages of extending the culture to five or six days after egg collection
- if blastocyst culture is selected, the woman will return to Midland Fertility for her fresh blastocyst transfer five or six days after her egg collection, depending on the rate the embryos develop
- she will know if she is pregnant within 10 days of the blastocyst transfer
- blastocysts which are not transferred at the fresh embryo transfer stage may be frozen and stored for possible future use
Are there any disadvantages or risks of blastocyst transfer?
- not all embryos develop to blastocyst stage. Some fail to continue to divide and cannot be transferred at all, or the embryologist may recommend transferring the embryo earlier than five days after egg collection, at around four to eight cells
- data from around the world shows an increase in the incidence of identical twins from pregnancies resulting from blastocyst transfers, from 0.25% (natural conception) and 0.7% (IVF/ICSI) to approximately 3.9% with blastocyst embryos
- no other risks are currently evident although some may not be known for several years.
There is no charge for this procedure as part of IVF and ICSI treatment at Midland Fertility
Go to the Midland Fertility Patient Treatment Information page and download the following infosheets:
- Blastocyst Transfer
- Embryo Transfer Policy and SET
- IVF: In Vitro Fertilisation
- ICSI: Intra Cytoplasmic Sperm Retrieval
- Embryo Freezing