Wednesday, January 14, 2004

Multiple ovulations?

Yesterday I described a study showing that women have more than one wave of follicular development per reproductive cycle (see the post here). Interestingly, some media reports have included that the same study showed conclusively that women can ovulate more than once per ovarian cycle. The New Scientist and AZCentral both state that 6 of 63 women ovulated more than once (thanks to Amity Wilczek at Nature is Profligate for finding these, and for discussion that helped with this post). MSNBC states that 13 of 63 women ovulated more than once "in various different ways."

What's odd about these statements of multiple ovulations is that I can't find any reference to these data anywhere in the paper. The abstract includes data on only 50 women, the journal's summary of the research makes no mention of multiple ovulations, and even the press release I found doesn't mention multiple ovulations. Amity Wilczek found the full paper and says that it doesn't mention anything about multiple ovulations either (other than saying that the 50 women only ovulated once).

The paper does include that there were 63 women in the study, with 13 removed for various reasons. The reason those 13 women were removed were "1 woman had an interovulatory interval less than two standard deviations from the mean, 4 women exhibited luteal phases shorter than two standard deviations from the mean, 1 woman had an ovarian dermoid cyst, and 7 women developed an anovulatory follicular cyst, hemorrhagic anovulatory follicle, or luteinized unruptured follicle during the study" (quote from Amity Wilczek at Nature is Profligate).

So, I'm left wondering where these data on multiple ovulations are coming from. Are they in a separate paper that the articles aren't citing? Are they included somewhere in the paper and I'm just missing them? Is it a misinterpretation of the paper? Or do these data just not exist? A mystery indeed ...

1 comment:

Radagast said...

Importing comments:

I'm still mystified by all of this. I did a Science Citation Index search too to see if Pierson had any more recent papers about human ovulation that might be the source for these numbers. Nope.

I had one more thought, which was that perhaps a six of the women ovulated more than one egg in their final, ovulatory "wave." Again, I see no explicit mention in the paper. And this type of double ovulation has very different implications for human fertility than would ovulations at different periods during the menstrual cycle.
When interviewed, the authors do seem to expect that these "waves" would sometimes result in multiple ovulations (for instance here,,where they say this can explain dizygotic twins with different conception dates).
January 14, 2004, 4:52:47 PM PST