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SEEKING Jewish Egg Donor: 21-30, very slender, brunette, healthy, educated, high SATs. BORN JEWISH.

If you’ve seen ads like this one—which have appeared right here in j. — then you know that the Jewish egg is a hot item these days.

I almost want to start this column with a really bad egg joke, like “What does the chicken say to cross a busy street?”

“EGGS-cuse me, please.”

But let’s get serious. Local infertile couples these days are paying $5,000 and up to get hold of a Jewish egg. The ads put the money up front, and I’ve verified the prices at fertility centers.

Never in my life, however, did I imagine that I’d be propositioned for one of my eggs, as I was recently at a birthday party. A handful of kids were gathering around the tree to hit the piñata, when a voice carried over the whack of the stick.

“Your daughter is so beautiful!”

I turned to the mom next to me. I didn’t recognize her. “Thank you,” I said.

She introduced herself as the mother of one of the classmates of the birthday girl. When she told me her name, I recognized it. She is a writer, too, and I’d seen her byline in a local paper. I asked about her job.

But she wanted to talk about my daughter, Mae: “Did you give birth to her here? What nationality is her father? — Oh, you’re a single mom — ”

I openly spilled the details of my personal life, something I often do and regret a moment later. I told her about the fact that my daughter went to a Jewish preschool and now after-care, and how important our Jewish community is.

“I want to ask you something,” this mom whispered to me, “but my husband would kill me.”

He was one of the safeguards at the piñata, making sure no one got hurt.

“What is it?”

“I can’t!”

“C’mon.” I was sure that she wanted to know if I was dating, so she could set me up with one of their friends.

She shook her head. “You might be insulted.”

“I won’t.”

“You see, we want a second child,” she told me, “but I’m too old. We’re looking for a donor. I’ve never just gone up to anyone and asked like this — ”

“I’m flattered,” I said.

And part of me really was. In a strange way, I felt that she valued me because I was Jewish. She didn’t even know me, but I was worthy somehow. She wanted my genes.

Still, I had to come clean. “I was raised Jewish, but my mother isn’t Jewish, just my father — ”

“No problem.” She handed me her card.

“Uh, I guess I can think about it,” I said awkwardly.

“Oh, please do!”

As treats poured out of the piñata and hit the ground, I thought: So, what makes an egg Jewish?

Judaism has always placed an emphasis on the family line, and aside from being formally converted, having a Jewish mother has been a requirement for calling oneself Jewish. But in the days of assisted reproductive treatments like egg donors, how do you define an egg as Jewish? What if the donor’s genes are not Jewish, but the mother giving birth is Jewish?

Dr. Isabelle Ryan, associate medical director at San Francisco’s Pacific Fertility Center tells me that they rely on an egg donor’s honesty. The donor undergoes “routine psychological ‘screening’ to help detect if she may be misrepresenting herself,” she says.

Still, I’m stumped about the identity of an egg. Egg donors come in all shapes and sizes. If a couple chooses to ask for, say, an Asian American or African American egg, the baby will have noticeable genetic traits. But it’s not like you can test an egg to see how Jewish it is.

“One’s self identity as ‘Jewish’ can take on many forms,” Dr. Ryan adds, “depending on one’s personal convictions, or those of the Jewish denomination one belongs to, those of the rabbi of that person’s temple.”

As for me, I’m not ready to be a donor. I’ll keep all my eggs in my own basket.