What Is the Hook Effect?

I got pregnant with my third child three months after the devastating loss of my second child. To say I was nervous was an understatement. At that time, I didn't know about the hook effect.

By about 5 or 6 weeks gestation I was certain I was losing another pregnancy. I wasn't just worried that I might. It was ,  to me , as clear as day that it was happening. Here's why:

Amazon sold super cheap pregnancy tests. I think they cost me about $0.25 apiece, and I had stocked up for my trying to conceive journey. My first child had taken a while to conceive. We had been lucky the second time, but I didn't know how long it might take.

When I got a faintly positive test after the first month of trying, I almost didn't believe it. It was too lucky to have conceived two babies in a row the first month trying. So I tested the next day. It was slightly darker, but I still wasn't convinced.

By the third day of testing, it was an obvious positive, though still astronomically fainter than the control line. I developed a daily ritual of peeing on a stick to watch the line get darker. And it did.

This was a good sign. Darkening lines meant that the baby was implanting properly. At least so said the internet forums I was frequenting for reassurance.

The control line soon became the lighter of the two lines. Everything was progressing nicely. I lined up the tests and wrote the date on each one.

Then, one day, the line didn't get darker. In fact, the line was slightly lighter than the day before. I rushed to my phone to query the Facebook mom's group de jour I was following.

"It's probably just the concentration of your urine. If you drank a lot, and it's less concentrated, it will show as lighter."

I breathed a sigh of relief. A logical explanation. I could live with that. But the next day it happened again. And again. And again. For over a week more I tracked my urine diligently, holding a silent vigil for the baby I thought was gone. The line faded into obscurity, to the point it was hard to see anymore.

"I'm sorry. That sucks," said everyone.

And it did. It really did. I was losing another child. One I had only had for such a very short time, and I wasn't prepared emotionally. Except…

…I wasn't losing the baby. I expected bleeding, but it never came. I took to Facebook again to ask people how long it would take for the process to start (I had never experienced an early pregnancy loss, and my daughter needed to be induced after her death) and someone asked me:

"Have you heard about the hook effect?"

No. I had not. It only took me about a millisecond to open my browser and google it.

The hook effect occurs when you have too much hCG (the hormone the pregnancy tests detect) in your urine. It overwhelms the test, and the antibodies that are supposed to bind to the hormone can no longer do so effectively. It can lead to false-negative pregnancy tests, or in my case a consistent fading every day, to a near negative test.

The way to tell if you are experiencing the hook effect is to dilute your urine and see if the line shows up any darker. I tried different dilutions of my urine and sure enough, the more I diluted the urine, the darker the test became. Once I had diluted it ten times, the pregnancy test displayed a fairly strong positive.

I stopped testing that day. It wasn't the last scare . The pregnancy was complicated, but in the end, it resulted in a healthy infant who is now almost three years old!

I wish I had known about the hook effect at the beginning of my pregnancy after loss journey, but I am super glad someone shared that information with me when they did. I had lost hope, and they gave it back to me. In sharing my story, I hope that it will save someone else the emotional turmoil I felt because of the hook effect.

*post first appeared on Medium

Julia Marsiglio is a Canadian author who writes poetry, fiction, and non-fiction exploring topics such as trauma, grief, mental health, marginalization, and neurodivergence.