Scientists Have Just Worked Out How to Find the Best Eggs for In Vitro

Scientists can see a spark at fertilization that has serious implications for in vitro.

Scientists at Northwestern’s Feinberg School of Medicine have just witnessed something amazing that happens when a sperm connects with an egg: Sparks literally fly. Zinc sparks. This electric event has been witnessed before in mice, but it’s the first time anyone’s seen and photographed it during human fertilization, and it could represent a significant advance in the success rate of in vitro fertilization.

The team injected an egg with sperm enzyme. (The use of actual sperm in experiments is illegal.) Doing this triggers an increase in calcium within the egg that then causes zinc to be released. The zinc binds to small molecule probes, that emit light that can be seen under a fluorescence microscope as a spark. From there, millions of zinc molecules explode momentarily all around the outside of the egg.


  • Northwestern
  • Being able to observe all this, and non-invasively, is important because zinc is critical for the development of a healthy embryo, and Northwestern has previously established that zinc is actually what triggers an embryo to grow and change into a distinct new organism, that is, a new person. 

    “This means if you can look at the zinc spark at the time of fertilization, you will know immediately which eggs are the good ones to transfer in in vitro fertilization (IVF),” according to Teresa Woodruff, one of the study’s two senior authors. “It’s a way of sorting egg quality in a way we’ve never been able to assess before.”

    Study co-author Eve Feinberg adds, “There are no tools currently available that tell us if it’s a good quality egg. Often we don’t know whether the egg or embryo is truly viable until we see if a pregnancy ensues. That’s the reason this is so transformative. If we have the ability up front to see what is a good egg and what’s not, it will help us know which embryo to transfer, avoid a lot of heartache and achieve pregnancy much more quickly.” 

    The bottom line? Francesca Duncan, first author of the study and the person who first discovered the human zinc spark, says the breakthrough “will help us address one of the largest unanswered questions in reproductive medicine—what makes a good egg?”


  • Headline image: Northwestern

    How getting in sync with your partner can lead to increased intimacy and sexual desire

    Researchers discover a link between nonverbal synchronization and relationship success.

    Sex & Relationships
    • Scientists say coordinating movements leads to increased intimacy and sexual desire in a couple.
    • The improved rapport and empathy was also observed in people who didn't know each other.
    • Non-verbal clues are very important in the development stages of a relationship.
    Keep reading Show less

    How humans evolved to live in the cold

    Humans evolved to live in the cold through a number of environmental and genetic factors.

    Image source: Wikimedia Commons
    Surprising Science
    • According to some relatively new research, many of our early human cousins preceded Homo sapien migrations north by hundreds of thousands or even millions of years.
    • Cross-breeding with other ancient hominids gave some subsets of human population the genes to contend and thrive in colder and harsher climates.
    • Behavioral and dietary changes also helped humans adapt to cold climates.
    Keep reading Show less

    Setting a maximum wage for CEOs would be good for everyone

    Could this be the long-awaited solution to economic inequality?

    Apple CEO Tim Cook looks on during an Apple special event at the Steve Jobs Theatre on the Apple Park campus on September 12, 2017 in Cupertino, California. (Photo by Justin Sullivan/Getty Images)
    Politics & Current Affairs

    Under capitalism, the argument goes, it's every man for himself. Through the relentless pursuit of self-interest, everyone benefits, as if an invisible hand were guiding each of us toward the common good. Everyone should accordingly try to get as much as they can, not only for their goods but also for their labour. Whatever the market price is is, in turn, what the buyer should pay. Just like the idea that there should be a minimum wage, the idea that there should be a maximum wage seems to undermine the very freedom that the free market is supposed to guarantee.

    Keep reading Show less