Reproductive rights advocates are frustrated that none of the seven televised Democratic debates so far have asked any questions about abortion rights. But while it wasn't an official Democratic debate, Monday night's Fox News town hall finally asked both candidates direct questions about abortion in a public forum.

This is important, because abortion in America is a lot more complicated than whether a candidate supports Roe v. Wade and the "right to choose." States have passed more anti-abortion laws in the past five years than they did in the previous two decades, and some of those laws are being challenged at the Supreme Court. These laws affect whether a woman can afford an abortion, how late she can get one, and whether she can access one in her own community or whether she'll have to cross state lines.

And Clinton and Sanders's differing answers on abortion at the Fox town hall showed why it's important to ask candidates about the issue, even pro-choice Democrats.

Bernie Sanders refused to support any specific abortion restrictions

"Can you name a single circumstance at any point in a pregnancy in which you would be okay with abortion being illegal?" moderator Bret Baier asked Sanders during his time on stage.

"It’s not a question of me being okay," Sanders said. "I happen to believe that it is wrong for the government to be telling a woman what to do with her own body. I think, I believe, and I understand there are honest people. I mean, I have a lot of friends, some supporters, some disagree. They hold a different point of view, and I respect that. But that is my view."

Sanders pivoted to his frustration with Republicans who want to "get the government off our backs," yet "somehow on this issue, they want to tell every woman in America what she should do with her body."

Baier followed up: "I guess the genesis of the question is that there are some Democrats who say after five months, with the exception of the life of the mother or the health of the baby, that perhaps that’s something to look at. You’re saying no."

Sanders's answer suggested that he had no interest in haggling over restrictions and exceptions: "I am very strongly pro-choice. That is a decision to be made by the woman, her physician, and her family. That’s my view."

Hillary Clinton got more specific, and more equivocal

"Do you think a child should have any legal rights or protections before it’s born?" Baier asked Clinton. "Or do you think there should not be any restrictions on any abortions at any stage in a pregnancy?"

Clinton started by discussing the Supreme Court decision "that would shut down a lot of the options for women in Texas," as well as "other legislatures that have taken similar steps to try to restrict a woman’s right to obtain an abortion."

The right to an abortion under Roe v. Wade is "not much of a right if it is totally limited and constrained," Clinton said. "So I think we have to continue to stand up for a woman’s right to make these decisions, and to defend Planned Parenthood, which does an enormous amount of good work across our country."

Baier pressed. "Just to be clear, there’s no — without any exceptions?"

"No — I have been on record in favor of a late pregnancy regulation that would have exceptions for the life and health of the mother," Clinton said. "I object to the recent effort in Congress to pass a law saying after 20 weeks, you know, no such exceptions. Because although these are rare, Bret, they sometimes arise in the most complex, difficult medical situations."

Like "fetal malformities [sic]?" Baier asked.

"And threats to the woman's health," Clinton said. "Under Roe v. Wade, it is appropriate to say, in these circumstances, so long as there's an exception for the life and health of the mother."

What their answers mean

It's no accident that Baier asked about abortion restrictions after five months of pregnancy — or 20 weeks, which is halfway through the second trimester.

Twenty-week abortion bans are very popular among anti-abortion lawmakers. Congress has repeatedly tried and failed to pass such a ban, and 12 states have succeeded — but several courts have blocked these laws on constitutional grounds.

Roe v. Wade says you can't ban abortion before a fetus is viable, and the medical consensus is that 20-week fetuses are not viable. That's why if the Supreme Court ever decided to rule on 20-week bans, it could mean a new challenge to Roe.

Supporters of 20-week bans say they're necessary because fetuses can feel pain by then. But the medical consensus doesn't support that view either, and doctors note that many serious fetal anomalies can't be diagnosed until the 20-week ultrasound.

Sanders didn't explicitly say that he'd veto a 20-week abortion ban, but his answer and his record of blocking similar laws make it pretty clear that he doesn't support them.

Clinton's answer on later abortion was less clear. For instance, by "late pregnancy regulation" did she mean after 20 weeks, or later?

She said she opposed 20-week bans that don't have adequate exceptions for a woman's health — and most Republican-sponsored 20-week bans do indeed fall short on this. But it wasn't clear from Clinton's answer whether she'd support a 20-week ban that did have adequate health exceptions.

The Clinton campaign later clarified to Vox: "Hillary Clinton is on record and continues to oppose 20-week abortion bans, which are a direct challenge to Roe v. Wade and therefore unconstitutional. ... She also recognizes that Roe v. Wade provides that restrictions are constitutional later in pregnancy so long as there are clear exceptions for the life and health of the woman."

That's consistent with what Clinton has said in the past, both about 20-week bans and about later abortion restrictions in the third trimester that are consistent with what Roe v. Wade allows.

Abortion opponents often ask pro-choice people about aborting 8- or 9-month-old fetuses to press them into drawing a clear legal line, which seems to be what Baier was trying to do. Marco Rubio did this more explicitly when he claimed during a GOP debate that Clinton supports abortion "even on the due date."

She doesn't — and as OB-GYNs will tell you, "due-date abortions" are not actually a thing. Reputable doctors only end a very late pregnancy if there is a problem, either by inducing labor or performing an expensive four-day procedure.

What the answers say about the candidates

The differences between the candidates' answers on abortion were like the differences between their answers on a lot of issues.

Sanders came across as more unwavering and moralistic, but also less specific. Clinton came across as more cautious and equivocal, but also more interested in nuance and policy. Given the realities of medicine and Roe v. Wade, it's not clear how different their positions on later abortion really are in practice — but Sanders seemed less willing to concede that any restrictions would be valid.

Abortion rights advocates were pleased with both answers, but some thought that Clinton told a clearer story about how abortion rights are under attack.

"Both candidates unequivocally stated that they support a woman's right to make her own decisions, and that's a good thing," said NARAL Pro-Choice America president Ilyse Hogue, whose organization has endorsed Clinton, in a statement. "And we are so grateful to Hillary Clinton tonight for, once again, focusing the nation's attention on the current crisis in abortion access facing this country, even when asked a question that is not relevant to the experience of the vast majority of the one in three women in this country who have had an abortion."

It's true that the question only applied to the roughly 1.4 percent of abortions that happen after 21 weeks. But it was still revealing, and showed why moderators shouldn't ignore the issue.