more on donor problems, but less on meiosis
1 Replies
teri-chan - July 13

I'm making this a separate post, since I imagine the stuff on meiosis isn't so interesting to most undergoing infertility treatments. But this question might be of interest to others.

I was told that only 3 of the 14 eggs retrieved from my donor were mature. I take it that means that only 3 of the 14 had achieved "nuclear maturity". You said that the most likely explanation for this low ratio of mature eggs to retreived eggs is that the donor took the hCG shot later than she should have.

I was also told that only 1 of the 4 eggs that were ICSI-ed (and I'm assuming that a 4th egg acheived nuclear maturity in the lab and hence was able to be ICSI-ed) fertilized. You said that the low fertilization rate indicates that the eggs may not have achieved cytoplasmic maturation.

What is responsible for cytoplasmic maturation? Is it also linked to the timing of the hCG shot or is it a separate matter, related for example to the length of the stimulation? (It was an 11 day stimulation.)



Dr Smith - July 14

You are correct that the definition of maturity at the time of retrieval is "nuclear" maturity, since an egg that has not reached metaphase II cannot be ICSI'd.

The egg must have also completed the cytoplasmic maturation process in order to "respond" to the sperm, show signs of fertilzation the next day and continue development. Just because an egg exhibits nuclear maturity does not mean that it has completed cytoplasmic maturation. These processes can be out of synch with each other in stimulated cycles. Although it is common to have a few dissynchronous eggs in every batch, your donor's eggs were really out of whack. Something went realy, really wrong.

The process of cytoplasmic maturation occurs in the follicle throughout the entire stimulation phase (8-11 days). It occurs indirectly under the influence of FSH and LH. I say indirectly because the FSH and LH work through the follicular cells that, in turn, change the conditions inside the follicle to facilitate egg maturation. The cytoplasmic maturation process involves many factors (known and unknown). It is very complicated. There are a few people studying this process in animal models, but whether or not this will translate to humans remains to be seen.



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