Science of Love, Sex, and Babies

Your right ovary rules

Posted in news by jenapincott on July 13, 2009

200028164-002cropIf you’re like most women you probably think ovulation is something of a meritocracy — that both ovaries do equal work, and that they alternate every cycle.

If by chance you were not taught that the ovaries soldier on left-right-left-right, then you probably think ovulation is random, like a coin toss.

The second scenario is closer to the truth, but it’s not the whole truth. At least not all the time or for most women.

Fact is, your right ovary is likelier to ovulate more often than the left. This means that in two consecutive months, the right side is probably the one doing more of the hard work of producing the dominant follicle that could become a baby.

At least this is what multiple studies have found, including here (57.7% of women have right-side ovulation), here (54.5 percent have right-side ovulation), and here (62% of total follicles are on the right), and here (larger, more numerous follicles).

Why is the right ovary often dominant?

Anatomical asymmetries between the left and right sides are thought to be the reason. The left ovarian vein drains to the left renal vein and the right ovarian vein to the inferior vena cava. The left renal vein is thought to be under higher pressure than the right and therefore drains slower. Because the left ovary drains slower, the collapsed follicle (called a corpus luteum) takes longer to clear and thereby diminishes the chance that ovulation will occur on that side the following month. No such condition exists on the right side, which is why successive right-side ovulation is more common. Estradiol and testosterone levels are also higher during a right-side cycle; this may also be related to the right ovary’s more efficient plumbing as it flushes lining-plumping hormones into the uterus.

All this leads to some fascinating statistics. For instance, right-sided ovulation favors pregnancy more often than left-sided ovulation (64 percent of pregnancies came from women’s right ovaries), according to a study in Japan that tracked nearly 2,700 natural cycles. Then again, according to another study, odds of pregnancy are best when the dominant follicle develops in the ovary opposite to where ovulation took place in the previous cycle (with pregnancy occurring more often in a right-side cycle that follows a left-side cycle) because the dominant follicles in such cycles are healthier. Even if the right ovary drains faster than the left, the corpus luteum left over from the previous cycle still negatively affects the hormonal health of the dominant follicle. Best to start with a clean slate.

Interestingly, researchers in another study speculate that right-side ovulation is dominant for most of a women’s reproductive years. Toward perimenopause women are more likely to become left-dominant, presumably because the supply of follicles in the right ovary has diminished.

Apart from ultrasound, there’s no reliable way of telling which ovary you’re ovulating from. ( I devote a section of BLONDES to why ovulation is concealed, even to women themselves.) If you think about it, perhaps that’s a good thing.

9 Responses

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  2. Susan said, on July 24, 2009 at 10:18 am

    I recently came across your blog and have been reading along. I thought I would leave my first comment. I don’t know what to say except that I have enjoyed reading. Nice blog. I will keep visiting this blog very often.


  3. LILA said, on January 4, 2010 at 6:20 pm

    It will be interesting if someone did a research on my hypothesis that you get a baby girl if your left ovary ovulates and baby boy if the right ovary releases the egg.This may be predetermined as well just look the Chinese gender prediction calender.I just thought that this may be it’s secret!Would love to hear more about it!

  4. conceive a baby boy said, on February 12, 2010 at 11:23 am

    Wonderful Web site! I wanted to ask if I could web page few things for a term paper.

  5. Angeia Hayes said, on March 19, 2010 at 10:18 pm

    I just found out that I am pregnant, only after my first baby is 9 months old and I was still nursing him!! Anyways, when I went in for the sonogram she told me it was a left ovary baby, which I thought was very intresting!! Just a fun fact I am putting in the baby book, heart rate was 176.

  6. Have a Baby Girl said, on April 11, 2010 at 7:44 pm

    Left, right, I doubt it makes any difference. I feel there is some truth to some of the gender selection methods though. Just to many people who are successful in choosing one sex over the other.

  7. Allison said, on February 15, 2011 at 12:26 pm

    Interesting — I only ovulate from my right ovary. It’s the only one I have. 🙂 I wonder if that makes me more likely to get pregnant, then?

  8. Rebu said, on April 5, 2011 at 1:02 am

    Dear Mam/Sir
    Please consult me about following reports. I thinking, i am going to preparing a baby since a years but i cant succeed. So that i cheched up a Dr., Dr.s report shows below. i would like to request u, what can i do after check up. hope that you will be help me in this matter because i am so worry about it.

    Hope i get reply soon. and waiting your reply.
    Thank you for your kind cooperation.
    Date Day RT. OVARY LT. OVARY
    22/01/11, 12th F1 = 5*6; F2= 4*4; F1= 3*3; F2= 2*2
    F3= 3*3; F4= 4*4; F3= 2*2; F4= 2*MM.

  9. Susmita Chouhan said, on May 14, 2011 at 6:32 am

    Dear Mam/Sir,
    I want to know what the Dr. report is, my shows below like this on 12th day Endometrial thickness: 07mm. Right ovary: Dominant follicle is 18mm X 14mm.
    Left ovary: Dominant follicle is 17mm X 17mm. No free fluid is seen in cul-de-sac.
    and on 13th day report is Endometrial thickness: 08mm. Collapse of dominant follicle on left partial collapse of one on right seen (12mm X 8mm)
    Fluid in POD++
    OPINION Follicular rapture on 13th day. this is all about my report for this month, hope you will be help me in this matter because I want to have a baby.

    Hope I get my answar soon,

    Thank You.

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