When a Twin Disappears

Editor’s Note: This article previously appeared in a different format as part of The Atlantic’s Notes section, retired in 2021.

A reader revives our collection of miscarriage stories with an uncommon case of her own—two cases, in fact:

Thank you so much for the series on abortion you carry, Chris—turning the abstract (which is very easy to judge, from a distance) into real-life stories, of real-life people. The many stories exemplify that there is no “one-size-fits-all” in this matter—that people’s lives tend to have many nuances that, when judged from a distance, are easily overlooked.

I have two healthy children, but it took us years to conceive, and we were helped by fertility treatments. [See many infertility stories from readers here.] My first pregnancy ended in an early miscarriage, around the 6-to-8-week mark. Same for my third pregnancy.

In both cases I never felt like I lost a child; rather, I grieved because of the missed opportunity. Fertility treatments are usually like that. In many cases, you need several trials before having one that takes.

Early in my second pregnancy, the doctor could see I was pregnant with twins, with one of the twins showing delayed development. The doctor told me to just wait and see what happened, and so I did.

In our next check-up, we saw that one of the twins had vanished.

Exactly the same thing happened with my fourth pregnancy: Initially we saw (identical) twins, with one of them being less well developed than the other. I had read enough about twin pregnancies to know that one of the twins being less developed may be a liability for the pregnancy as a whole. When one of the twins dies in utero, it may “poison” the other one, so to speak, resulting in a miscarriage of both.

I have never considered—not for one second—the losses early on in my pregnancies (the miscarriages, the vanishing twins) as “children lost.” Rather, I was happy to have the totality of my attempts resulting in two healthy, beautiful children. I feel very blessed.

I think it’s because of my fertility treatments that I could witness up close some of the varieties that nature has up its sleeve. If I hadn’t had the many early check-ups that come as part of the treatments, I would’ve probably thought my period was late that one month, and I would never have known about the twins.

Here’s some basic information on vanishing twin syndrome, which usually goes undetected because one of the fetuses disappears so early in the pregnancy, absorbing into the mother’s body or even the other fetus:

Vanishing twin syndrome has been diagnosed more frequently since the use of ultrasonography in early pregnancy [especially when fertility treatments are involved, as in the case of our reader]. Estimates indicate that vanishing twin syndrome occurs in 21-30 percentof multifetal pregnancies. … Analysis of the placenta and/or fetal tissue frequently reveals chromosomal abnormalities in the vanishing twin, while the surviving twin is usually healthy. Improper cord implantation may also be a cause.

In rare cases of vanishing twin syndrome:

The fetus becomes “mummified” in the uterine membranes and is discovered during delivery. This is called a “fetus papyraceus,” and it’s exceedingly rare. In other cases, the surviving baby takes on some of the lost twin’s cells and becomes a chimera—one person with two sets of DNA.

Microchimerism—when cells from a fetus remain in the mother, sometimes for decades—was covered in The Atlantic by Vanessa Hua:

In research published [in 2014], epidemiologists analyzed the data from a previous longitudinal study of 272 elderly Danish women. Out of that group, 70 percent had Y sex chromosomes in their blood, a sign of the presence of male cells.

Although cardiovascular disease was slightly elevated among women with male microchimerism, their overall mortality rate was a whopping 60 percent lower, primarily because of a lower incidence of cancer. Eight-five percent of these women made it to age 80, compared to 67 percent of women without the presence of these cells.

Scientists don’t know for certain what biological mechanisms cause these findings, but past research suggests microchimerism may boost immune surveillance—that is, the body’s ability to recognize and destroy pathogens and cells that might become cancerous—and also play a role in the repair of damaged tissue, helping form new blood vessels to heal wounds. Microchimerism is also associated with a lower risk of Alzheimer’s disease and breast cancer.

Read the rest here. In the comments section of that piece, Kelly Kittel offers a poignant passage:

I wrote about this fascinating topic in the prologue of my memoir, Breathe, which is about motherhood, grief, and family conflict. To quote, “Recently, I learned about microchimerism, which is the presence of cells in one person’s bloodstream that originated from a different person and are therefore genetically distinct from the other cells swimming around them. In humans, the most common form of this is called fetomaternal microchimerism. This occurs when cells from a fetus pass through the placenta and establish cell families within the mother. As far as we know, these fetal cells remain and multiply for several decades, perhaps even forever. This means that swimming around in my body could be cells from thirteen different babies. I am the embodiment of my children, most of whom are otherwise dead. And as I’m carrying them, they, too, are carrying me. This also means that when my children died, a part of me died, too. I knew this. I felt this. I just didn’t know exactly why. And now I do.”

Another woman provides some further reading:

After losing two babies, this subject is not only fascinating to me but also important on a deep level. We’re all connected in ways we cannot imagine, ways science is only beginning to understand. I first read about microchimerism in an article titled “Mother & Child Are Linked at the Cellular Level,” which has a little more on the subject. I haven’t entirely gotten it out of my head since.