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Sunday, 20 July 2014

Embryo transfer: How many embryos is too many?

Once embryos are in culture, one or more of these need to be transferred into the uterus with the hope that nature will nurture the embryo and a pregnancy would result. Embryo transfer is a simple procedure much like an Intrauterine Insemination in which embryos are simply deposited in the womb cavity. Most often it is done under ultrasound guidance. Since the ultrasound is done on the abdomen, it is imperative that the bladder is full. 

The question is how many embryos should be transferred to achieve the optimal pregnancy chances? Logic dictates the insertion of as many embryos as are available! But does this really improve the pregnancy and what are the implications? The answer is that with the increase in the number of embryos that are inserted, the pregnancy after a certain point plateaus. In addition, there are higher chances of multiple pregnancies too. We have all heard of twins but triplets, quadruplets, and higher order pregnancies are also not uncommon!
There are practical problems of having to deal with a multiple pregnancy, but there are also serious risks (to both mother and the babies) associated with a multiple pregnancy. These risks exponentially rise with the number of embryos that are growing. As such Fetal reduction is usually recommended whenever the pregnancy is of higher order than twins. This option is unthinkable and unacceptable for many and therefore best prevented. 

The easy solution is to put in less number of embryos! Of course this has to be done cleverly so as to not let the success rate take a hit. This decision is best taken in consultation with the fertility specialist and embryologist, taking into account, the age and medical history of the woman, the number and quality of embryos and the budget of the couple. Where the couple are adamant in avoiding even twins, they can opt for the transfer of a single embryo at blastocyst stage. Any surplus embryos can be frozen for later transfer.

Sunday, 6 July 2014

Grading of embryos

The embryos are graded morphologically - the way they look under the microscope. The grading of embryos is done in order to identify the embryos with the best potential to implant and lead to a pregnancy. But please remember, it is only an indication, we all see embryos of the best grade failing to lead to a pregnancy while lower quality embryos can also grow into a pregnancy.

The ideal embryo at the Day 2-3 stage should have blastomeres  (cells of embryos) that are uniform in size and should have no fragments or leaked out contents of the cell during the division process. The ideal cell number on the second day of embryo's life (two days after the egg collection) is 4-cells while the cell number should be as close to 8 cells on the day 3 stage. Embryos that are slower or faster are marked down as are embryos that have unequal blastomeres or fragmentation.

It is also important to realise that the grade has no bearing on the normality of the embryo formed. In other words, the best grade embryo may be chromosomally abnormal and a poor grade embryo may be normal. Different labs use different grading systems and so please ask your lab to explain what their grading system is.

Tuesday, 1 July 2014

Embryo culture

Embryo culture involves incubating embryos till the time of their transfer into the uterus. After the appropriate method of fertilisation (IVF or ICSI) the eggs are left undisturbed in the incubator to allow the process of fertilisation to occur. There are accepted norms in identifying the days around embryo culture. The day of the pickup is called Day 0. The next day (when fertilisation is checked) is the first day of an embryo's life and this is called Day1. From here the days are counted serially.
Once fertilisation occurs, the genetic material carried by the egg and the sperm align together (the structure is called Pronucleus) and then fuse. In case the number of pronuclei is 3, these are abnormal in the amount of genetic material present in them and so these are discarded. The single cell of the embryo now starts dividing and the cell number (the cells of an embryo are called Blastomeres) starts increasing.
The ideal number of blastomeres is four on day 2 and eight on day 3. On the day 4 the embryo looks like a tight ball of cells. This day is a very dynamic stage and a lot of changes occur in the embryo. By the day 5, the cells have split into two groups, several of the cells align themselves on the periphery of the sphere that is covered by the egg shell - these ultimately play a role in implantation and form placenta. The others continue to stay in the form of a tight ball of cells at one pole of the embryo. These will ultimately form the baby. This stage of embryo on the day 5 of its life is called Blastocyst. Embryo transfer is typically done on the days 2, day 3 or day 5.