UPDATE: Looks like a false alarm. Gothamist has now published this statement from the MTA: "Our Command Center tells me that at 9:22 a.m. a pregnant customer was removed from the 1st Avenue L station to Beth Israel Hospital."
There may be a second "train baby" today.
Gothamist is reporting that a woman gave birth on the L Train this morning. While there's no official word of the birth, the site has put together a nice roundup of tweets by people who either saw the woman "pass out" or who reported the actual birth.
One Twitter user thought the woman was having a seizure and called the conductor for help.
More details as they become available...