Just thought I'd write something on this in hopes of someone perhaps stumbling upon this information while searching for an answer.
Sejin and I had a lovely weekend in the countryside for his grandmother's birthday. Sejin's family, the Jo's, come from Mungyeong, a rural, picturesque part of Korea that not a lot of foreigners venture to. More on Mungyeong later...
After arriving in Mungyeong and meeting his family (grandparents, aunts, uncles, cousins) at a restaurant in Mungyeong Saejae Provincial Park, we headed to our room upstairs (minbak) where everyone sat around eating snacks and fruit near the air-conditioner. Sejin's grandmother had made "sook," a type of bread/rice cake which is green and really doesn't have much taste. I was really full from lunch, so politely refused about three times, but after some coaxing, had a little piece, because after all, grandma had made it.
I did ask Sejin what was in it, but although his English is quite good, he's no botanist, so he could not tell me exactly what herb was in it. Actually, I found out after an Internet search that "sook" is made from mugwort, a herb that should be avoided by pregnant women. It can cause uterine contractions and preterm labor. Luckily, I had only eaten a very small piece, so I'm sure everything is fine. From what I understand, small amounts of mugwort are used in sook, mainly for colouring, and it's boiled beforehand, which removes much of its toxicity.
Later in the day, I wanted to get out of the minbak where everyone was sprawled out on the floor napping. Sejin and I took a short walk to a nearby building which was selling products made from "omija" (오미자), a local specialty in Mungyeong. From what I understand (I always say this because I just can't understand everything!), omija is the berry from a plant found in Asia. It's a pretty, bright red berry. I've had omija tea before and it's quite good. We were browsing all the products made from omija...tea, bread, wine, etc. Sejin chose a bottle of omija extract. We were paying for it and the lady at the counter informed us that pregnant women should not eat omija. I was impressed with two things: she had noticed that I was pregnant -- a first! yay!; and she actually spoke up to warn us. I was grateful for that.
So, in one day visiting the countryside, I encountered two potentially dangerous herbs used in traditional oriental medicine. And they weren't mixed up in some kind of weird potion that would make me wary of them. Koreans have a long history of using herbs and other plants that we in the west don't often use. They're so used to them being around, that they're not even sure what all of them can do/cause. Every spring, my mother-in-law serves up a traditional spring meal made almost entirely of herbs she went and picked herself. Some of them don't even have English names... Of course, I know Sejin's family, or any Korean, would not give me anything meaning to cause harm, but it's better to be safe than sorry.