The mothers-to-be arrived with swollen bellies. Sometimes their bumps were so big that I knew immediately it was too late, and I would have to turn them away. “How many weeks?” I’d ask. Some of them would lie. “Only 12, maybe 13,” one told me not so long ago. I did the exam. She was in her third trimester. It was far too late.

They don’t always mean to lie. It’s hard to get a pregnancy test around here. It’s hard to get anything around here. Food, clean water. It’s a miracle they get pregnant with so much malnutrition.

And I was expected to perform a second miracle. Often, I did. I had the tools. Namely, a long needle with the payload. Before injecting it into the amniotic fluid, I would always make sure to ask each woman one last time. “After I do this,” I would say, “you know you will be sending your child away. You will never see them again.” Some would cry as they nodded their heads to say Yes, I understand, please do it anyway. When I saw them do that, I would think of my biological mother and how she once made that same choice.

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I would come down here from the north under the guise of a medical mission. “I’m part of the Healthy Babies Worldwide Initiative,” I’d explain at the border. Sometimes they would open my doctor’s bag and see the syringe vials. “Those are the vitamins,” I’d add, pushing documentation in front of them. It wasn’t a total lie. Some of the vials did contain vitamins. But not the ones that really mattered.

How many women did I inject? Over the past five years it’s probably been about 6,000. I would have liked to keep count properly, but that would have meant leaving a paper trail and I wanted to avoid that. I would have done more if I could have visited more often, and if I had had more of the HelixSure to inject. But I had to be careful about stealing it from the lab in Bethesda where I worked.

I joined the lab about 40 years after the HelixSure programme began. The United States was the first country to demand that all pregnant women receive the HelixSure injection if they wanted their babies to be certified as citizens. And it had to happen before the second trimester. That was the only way to ensure that the HelixSure gene would be well integrated into the baby’s DNA. The programme was heralded as a way to get rid of citizenship documents, which were getting easier and easier to fake. Several companies were already selling contact lenses with stolen identity irises. Others were offering laser surgery to remodel your fingerprints to match those of a legitimate citizen. But HelixSure was impossible to counterfeit.

My mother — the one I knew in the United States, anyway — was a bit of a radical. She raised me on her own. She told me where I came from. “One day you might travel there,” she’d say. “But make sure you go there with a purpose.” When I was young I didn’t know what she meant. I would just nod and go back to my books. She always gave me books. But she knew we couldn’t travel together. “They’ll give us a hard time,” she would say. And I knew what she meant.

Even though I had HelixSure in every cell of my body, my DNA didn’t match hers. I remember how, one time, an enforcement officer came upon us in a Walmart car parking lot and demanded to test our cells. The random Citizenship Test surprised my mom and me. We’d just been going to get an ice-cream cake for my sixth birthday. My mom was too old for HelixSure so she showed him her papers. Next he pricked our fingers with the HelixSure Reader. “She’s adopted,” she said sternly to the officer. He looked me over closely. It must have been August, because it was my birthday, and my skin must have been even darker from the summer sun by then. “Makes sense,” he said gruffly as he started walking away. We got lucky that day that he didn’t dig deeper.

I wonder if my mom had been grooming me for this mission here south of the border. She had always wanted me to be an obstetrician, and she was the one who sent me the advert six years ago about the job at the HelixSure lab. “They need someone like you, Maria,” she told me.

I came up with the idea of going south by myself. I’d read about how bad the conditions were there. Some news stories mentioned unthinkable risks that people took with their lives to cross to the north. And, increasingly, the conditions endured by non-citizens north of the border were equally deplorable — being held in what looked like nothing more than animal cages. My part of the mission was to bring the HelixSure and do the injections. I never arranged the adoptions. I won’t tell you who did. I have to protect their identity.

I’m not sure who tipped them off about me. I only know that I was arrested yesterday, and that the authorities will never find those 6,000 babies. Kids, many of them, by now. Up north, where it is better. Where there is food, and air conditioning to thwart the unbearable heat.

They’ve kept me in this humid prison cell south of the border. I’m not sure if I’ll be extradited back to the US. For now, I am just here, waiting in the city where I was born.