Thirteen Texas abortion clinics will be forced to close tonight after an appellate court upheld a stringent state law requiring all facilities to become ambulatory surgical centers.

This will leave Texas with 8 abortion clinics, all in urban areas: Houston, Dallas, San Antonio and Austin.

Texas' House Bill 2 — the legislation that Texas Sen. Wendy Davis attempted to filibuster — had two main abortion restrictions. One was a requirement that all abortion clinics have admitting privileges at local hospitals. That piece of H.B. 2 went into effect in September 2013, and forced 14 clinics that could not obtain admitting privileges to close.

texas will now have 7 abortion clinics, all in major cities

The other H.B. 2 restriction required abortion clinics to become ambulatory surgical centers, essentially mini-emergency rooms that can handle complex medical situations. Ambulatory surgical centers, for example, must have wide enough hallways to fit a gurney and larger operating rooms than abortion clinics typically use.

the court found "no evidence" closures would impede abortion access

Abortion clinics in Texas have said that upgrading to these new standards would cost upwards of $1 million. They have argued that the new requirements are unnecessary as abortions tend to have a very low complication risk. Approximately 0.05 percent of first trimester abortions have complications that require hospital care. A Texas district court judge agreed with them and found that law to be an "unconstitutional undue burden on women."

But in the new ruling, the Fifth Circuit Court of Appeals overturned that opinion, finding the restriction constitutional. The three-judge panel found that Texas women will still be able to obtain abortion and that the longer travel distances would not unduly burden those seeking to terminate pregnancies. As evidence, they cited the fact that the admitting privilege law already shut more than a dozen clinics but that, in these new arguments, they did not see any "evidence that the previous closures....have caused women to be turned away from clinics."

The key metric in the Texas ruling: what's an undue burden?

The Supreme Court has, in previous rulings, articulated standards for judging the constitutionality of abortion restrictions. One key standard is whether a restriction places an "undue burden" on those seeking terminate a pregnancy.

The Supreme Court has previously defined an undue burden as a law with the "purpose or effect of placing a substantial obstacle in the path of a woman seeking an abortion of a nonviable fetus." The Supreme Court has previously ruled that laws requiring women to notify their spouses of their abortion, for example, are an undue burden as it could make it impossible for some women to access the procedure.

900,000 of texas' 4.5 million reproductive age women will now live 150 miles from an abortion clinic

In this case, a district court ruled that the Texas law was an undue burden because it meant women would have to travel much further to terminate a pregnancy. Approximately 900,000 of Texas' 4.5 million reproductive-age women will now live more than 150 miles from an abortion clinic.

But the Fifth Circuit panel disagreed: Texas women could, they argued, travel that distance and still find abortion accessible.

Correction: an earlier version of this story said there would be 7 abortion clinics left in Texas. While the court decision listed 7 clinics, there will actually be 8 facilities as Planned Parenthood has announced its intention to build an additional clinic.