As we read in the entry for the "Martyrs of Japan" in the online Catholic Encyclopedia (which you can access here), "There is not in the whole history of the Church a single people who can offer to the admiration of the Christian world annals as glorious, and a martyrology as lengthy, as those of the people of Japan." As this article from the Catholic Encyclopedia is a bit dense and lengthy, a here is a shorter, more concise article by a Modern Catholic priest named "Fr. Roger Landry."
But there are a few problems with the Rev. Landry article, as I will itemize below:
1) In paragraph six, the author speaks of "pregnant women" in his list of various types of Japanese martyrs, but the truth is that there were no other known pregnant martyrs in Japan or anywhere else in the 2000-year history of the Catholic Church other than Tecla Hashimoto, so why pretend that there were? It would seem that Rev. Landry is trying to water down the unprecedented nature of Tecla's pregnant martyrdom by speaking of a generic class of pregnant "women" that doesn't exist.
2) The mention of these presumed "pregnant women" is within a long list of various types of martyrs--"farmers, artisans, civil servants" and the like--as if to relativize the martyrdom of the only pregnant woman (singular) in the history of the Catholic Church. This sounds suspiciously like the Modern Catholic Church's attempt to relativize the uniquely horrific nature of abortion by lumping it into a group of various other social issues, such as housing, health care, and immigration issues, and telling us not to vote only on that one issue of abortion, a la deceased Modern Cardinal Bernadin's "Consistent Ethic of Life" (a.k.a. the "Seamless Garment").
It also seems like Rev. Landry is "sneaking in" the noun phrase "pregnant women" in the midst of a long list of other more typical kinds of martyrs, like a child in the confessional who hides his or her most serious sins among a whole lot of less serious sins. And usually said child will choose to put that most serious of sins in the penultimate place, as Fr. Landry has done, with the presumption that the list will be far enough along for that sin to go unnoticed, and neither at the actual end of the list, where it certainly will be noticed.
That being said, Fr. Landry must be given credit for putting "children as young as three" at the end of the list, just after the "pregnant women" mention, but if Landry is going to mention such young children at this point, then why not add the obvious "and, of course, a child in the womb"? It almost seems like the modern church--from Benedict the pope, to Yoshinao the bishop, to Landry the priest--are embarrassed about Tecla and the child in her womb, as if by being martyred as a pregnant woman she has done something that is very taboo.
3) The article positivistically supports the strategy of Benedict XVI to lump the 52 + 1 Martyrs of Kyoto into a much larger group of "Pedro Kibe and 187 Companions" (as if Tecla's group was not already large enough) for a beatification ceremony to take place in Nagasaki; which begs the question of why not having a group called "Tecla Hashimoto and Companions" with their own feast day on October 6 (the day they were killed), just as Nagasaki already boasts its own "26 Martyrs of Nagasaki" with their own feast day on February 6 (the day they were killed) under the title "Paul Miki and Companions"?