Sibling cycle, Take 1

Last post, I wrote about how Mr. Bunless and I have been (mentally) preparing for a donor-egg IVF sibling cycle using one of the three frozen embryos left from our amazing friend & egg donor, Marie. This has included some of the more usual stressors (e.g., when to start the cycle) as well as a few additional hurdles thrown in for good measure (e.g., an IVF doctor who’s gone MIA). Luckily, none of the extra challenges were showstoppers and we finally started the cycle protocol a couple weeks ago.

For those not intimately familiar with the ins and outs of IVF, this basically entailed stopping my normal hormone replacement therapy and starting on a high dose of estrogen (with progesterone added in to the mix once my uterine lining was confirmed to be sufficiently thick). Annoyingly, I never managed to convince a local clinic to do the monitoring for me, so we had to drive all the way to our clinic in Belgium just for a 30-second ultrasound and blood test. But thankfully, one check was enough, and we were booked in for our embryo transfer yesterday.

The transfer

Including all of the embryo transfer attempts leading up to our (now 2-year-old!) Miracle Baby (MB), this was transfer attempt #7, so we’re basically the frequent fliers of IVF clinics. Like the seasoned vet I am, I calmly chugged half my body weight in water** precisely two hours before the transfer, and breezed (/waddled) through registration and up to the appropriate waiting room. Mr. Bunless had to stay there due to COVID restrictions, which was the main difference with previous transfers. Otherwise, it was every bit as romantic as always: A female doctor wearing a headset repeatedly confirmed my name with the lab tech while jamming a catheter through my cervix. #magical

What I didn’t know beforehand was which of our three embryos we’d be transferring. Our clinic has a policy of defrosting an embryo at random, as they claim the grade only correlates with the potential to survive defrost and not with the actual pregnancy rate (although I still have a lot of questions about this). By sheer dumb luck, we ended up getting the three worst-quality embryos (from pre-freeze grade) for our first three donor-egg embryo attempts: an ungraded morula (which was actually the fresh transfer, but still failed), a 3CC blastocyst (which also failed), and a 3BC blastocyst (which turned out to be a stubborn little thing, consistent with the now two-year-old it would become). That meant our three ‘best’-quality embryos (one 4BB and two 3BBs) were still in the freezer waiting for us.

Yesterday, the embryo they transferred was the 4BB — i.e., our best one from the entire donor egg cycle. If the pre-freeze grade really doesn’t matter (which I’m still not convinced of), then this is inconsequential. However, it had developed to a 4AB after freeze, which is by-far the best grade we’ve ever seen. It’s still a game of statistics in the end, but I’m trying to remain cautiously optimistic (which, it turns out, is a whole lot easier to do when you’re not coming off the back of 5+ years of failed infertility treatments).

The embryo we transferred yesterday, pictured after defrost as a 4AB.

Can your uterine lining be too thick?

Just because I’m in a positive headspace so far does not mean I haven’t been driving myself crazy with google, as per usual. One of the things I’ve been stressing over is my uterine lining, which was already 16mm five days before transfer. Everyone knows that you don’t want your lining to be too thin, but apparently there is some research that too thick can also be a bad thing. There are some studies that argue ~11-12mm is optimal, with pregnancy rates falling for linings above that. Moreover, after posting about my epic 17mm lining in a previous cycle, I’ve since heard of clinics that will even cancel the cycle completely if your lining gets above 14mm. Was it really that detrimental? What did that mean for this transfer attempt?!

I couldn’t get much information out of my clinic (besides that they thought that my lining was ‘fine’), so I turned to my trusted friend Dr. Google. I indeed found several studies that show the pregnancy rate rises up until about ~11-12mm and drops again above that. However, the sample sizes were very small and there weren’t even any error bars included. (Disclaimer: still not a medical doctor, so speaking from my experience as a physicist.)

Then I stumbled upon this study, which is a much larger retrospective study (the largest to-date). They found that the live birth rate continues to increase with increasing uterine thickness and was actually highest in women with the thickest linings! The study comes with caveats, of course, but it was enough reassurance to at least stop my frantic googling. My take-away is that I can stop stressing about my lining being overly thick and go back to my regularly-scheduled stressing about whether every tiny sensation anywhere on my person is a pregnancy symptom.

See you all on the other side.


** Just to clarify, I didn’t literally drink half my body weight in water, but I did drink more than a liter (~32oz) in a span of 5 minutes, which was enough to make me feel (and look) 5 months pregnant.

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