The Supreme Court is expected to announce its decision Monday on Texas' abortion law, in what could be the most consequential ruling on the issue in a generation. The question: Do new requirements on abortion providers pose an unconstitutional "undue burden" on Texas women?

But among the reams of evidence presented to the high court and the public debate in Whole Woman's Health v. Hellerstedt, something is still missing: A full, official account of the initial impact of the law on Texas women.

A state employee with knowledge of the annual data Texas collects on abortion spoke to NBC News and is accusing state officials overseeing the Department of Health Services of intentionally blocking the information and instructing staff members to mislead people who ask for it. Because fact-finding traditionally ends after such a case goes to trial, long before it reaches the Supreme Court, the justices may or may not have considered it. But in the court of public opinion, the data could potentially undermine Texas' official argument that its requirements pose no particular burden on women.

First catapulted to the national stage by then-state Sen. Wendy Davis' pink-sneakered filibuster, the law has a bundle of abortion restrictions. Local abortion clinics have asked the Supreme Court to block two of the rules: that doctors performing abortions have admitting privileges at local hospitals and that even early procedures, including "medication abortions" that involve only taking two pills, take place in expensive ambulatory surgical centers.

Saying they are unable to comply with the admitting privileges provision — in one border town, McAllen, no hospital would even send abortion providers an application — about half of the clinics in Texas have already closed since 2013. If the Supreme Court allows the other requirement to go into effect, only nine or 10 clinics will be left in a state with 5.4 million women of reproductive age.

The court previously defined an illegal "undue burden" as "the purpose or effect of placing a substantial obstacle in the path of a woman seeking an abortion of a nonviable fetus." That's what makes information about the potential effect of the law so crucial, and it's why public health researchers and advocates are anxious to see Texas' data from 2014, the first full year the admitting privileges requirement was in effect.

Related: Texas women are running out of options

The state did release a provisional raw number of abortions in 2014, which showed a sharp decline in the procedure, but the full figures would break down the data by procedure, gestational age, region and race, which potentially corroborates the argument that the law poses an undue burden.

"The data is not final. If the data were final, we would release it. We hope to have it finalized soon," said Carrie Williams, a spokeswoman for the department.

But according to the state employee, who provided emails and screenshots to NBC News that appear to corroborate the timeline, the abortion statistics were in the final stages months ago. In fact, according to this individual, who spoke on the condition of anonymity because of ongoing employment there, in December 2015, researchers in the relevant department were actually told to get the information ready sooner than the usual 15 months.

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"They definitely wanted the abortion data earlier," the state employee said. The researchers went to work on finalizing the numbers, delivering them in mid-February to a supervisor.

It was a particularly high-profile moment for the 2013 law, known in Texas as HB2. The Supreme Court heard oral argument in the case on March 2, and the justices expressed particular interest in the evidence of how abortion patterns had changed in the state, including the chosen method of terminating a pregnancy and whether the changing number of clinics could meet the existing demand.

But they did so without access to the official Texas data. After weeks of silence, according to the state employee, a supervisor instructed the department to stop discussing the abortion statistics over email or phone and to respond to any requests for information by saying the numbers weren't ready.

In a June 15 letter, the ACLU of Texas, which first referred the state employee to NBC News, wrote, "Rather than responding honestly and claiming a legal basis for withholding the 2014 statistical tables, it appears that your agency has chosen to hide the truth." The letter continued, referring to Texas' state public records law, "Lying in response to Public Information Act requests would subvert the purpose of the Act, whether or not there is an arguable legal basis for withholding information."

Asked to respond to these allegations in detail, a spokeswoman for the Texas Department of State Health Services wrote in an email in part, "The 2014 tables are under review, and we hope to have them finalized and released soon. For the last several years, Texas abortion data was typically finalized and published between March and June."

Minutes later, when NBC News followed up specifically to repeat claims that the data release was being intentionally delayed and employees were told to pretend they were not yet ready, the only answer was an out-of-office message.

The information could also potentially undermine Texas' rationale for the law, which is that it makes women safer.

Related: Texas abortion clinics wait for the Supreme Court

Texas officials have told the courts that their intention was not to make abortion harder to access — which would almost certainly render the law unconstitutional — but rather to protect women's health. The American Medical Association and the American College of Obstetricians and Gynecologists submitted a brief to the court saying the law is medically unnecessary and actually endangers women by shuttering legal clinics and making them wait longer to see a doctor.

So far, the most comprehensive information about the impact of the law since it went into effect in mid-2013 has come from the Texas Policy Evaluation Project (TxPEP) at the University of Texas, which canvassed clinics directly about the first six months the law was in effect.

Dr. Daniel Grossman, a member of that research consortium and a professor at the University of California, San Francisco, was a key witness for the case against the law. He said he had no knowledge of whether the official information is being suppressed or delayed but did tell NBC News, "During the trial, Texas said our data couldn't be trusted because these weren't official statistics and that we had to wait for the official statistics to come out. It did seem ironic that they had the information."

In a series of published papers, TxPEP has found a more drastic drop in the overall abortion rate in Texas than the steadier nationwide decline, at the same time that the state cut family planning funds.

Crucial to the question of whether the law advances women's health, the researchers also found a "small but significant increase in the proportion of abortions that are second trimester," according to Grossman, suggesting women were facing longer waits or other hurdles.

"Abortion is safe in the second trimester, but it does have more complications and is more expensive and harder to find," Grossman said. "From a public health perspective, I think that's really very concerning if the proportion of later abortions is increasing because of HB2. These are the kinds of things that I think will be revealed in the official statistics."

TxPep researchers also reported a 70 percent decline in the number of medication abortions in Texas in the first six months after the law went into effect, even as health statistics show more women nationwide are choosing to end their pregnancies that way.

The state employee declined to provide the official data directly to NBC News, but according to the ACLU of Texas' staff attorney, Trisha Trigilio, the numbers indicated "an across-the-board drop in abortions. With respect to medication abortions, the drop was significant. There was a disproportionate drop in border communities."

All three data points are potentially relevant to the Supreme Court case. At oral argument, Justice Anthony Kennedy apparently referred to Grossman's data when he asked the Texas solicitor general about the finding that "this law has really increased the number of surgical procedures as opposed to medical procedures, and that this may not be medically wise."

A separate provision of the law, not before the court, specifically restricted the method Kennedy referred to as "medical procedures," or medication abortion. Women had to make up to four separate visits to a clinic, faced a smaller window of availability, and a higher, potentially riskier dosage of the pills involved. For women whose nearby clinics have closed, the additional visits in particular would have posed a potentially unconstitutional burden.

As for the geographical data, clinics in El Paso, Brownsville and McAllen, all along the Mexican border, closed when their doctors were unable to comply with the admitting privileges portion of the law. The clinics argued in their challenge that the law specifically burdened the disproportionately low-income and Latina residents there.

The state employee chose to come forward, the individual said, because of dismay that public information was being mishandled. "This is not political data," the employee said. "This is information that should be used for research or to make decisions about policy like the current Supreme Court case. It's not right."