A pharmaceutical company that has come under intense criticism for charging $1,500 a dose for a drug that reduces the risk women will give birth prematurely announced Friday that it was slashing the price of the medication.

KV Pharmaceutical of St. Louis announced it was cutting the price of the drug, sold as Makena, to $690 an injection. In addition, KV said it was expanding its program to help women who still are having trouble affording the medication.

“Ensuring access to an FDA-approved sterile, injectionable medication, manufactured under mandatory strict quality controls is in the best interests of all high-risk women,” Greg Divis, KV’s chief executive and president, said in the announcement.

Although the news was welcomed by some who had criticized the company, many said the price was still too high.

“While the new price may represent a significant reduction, it remains excessively inflated given that the original price was stratospheric,” said George Saade, president of the Society for Maternal-Fetal Medicine.

Makena, a recently approved drug to prevent preterm births. (KV Pharmaceutical Co.)

Several members of Congress said they still planned to investigate the drug’s pricing.

“While I am glad the company is taking a hard look at their prices, the proposed price reduction doesn’t go far enough to protect public health” Rep. Louise M. Slaughter (D-N.Y.) said. “This medication is still almost 50 times what it was a month ago.”

The March of Dimes, which has come under criticism for praising the drug’s approval before the price was made public, announced that despite the reduction it was severing its ties with the company. KV has donated about $1 million to the March of Dimes between 2006 and 2010.

“The company’s handling of the launch of Makena, and the initial list price, were highly unsatisfactory and unacceptable,” the group said in a statement. In a letter to the company, March of Dimes President Jennifer L. Howse asked KV to stop referring to her organization and using its logo in any promotional materials.

The Food and Drug Administration took the unusual step Wednesday of announcing that it would not stop pharmacies from continuing to produce less expensive versions of the drug, which had long been available for $10 to $20 a dose.

The FDA’s statement came a day after The Washington Post reported the controversy over Makena’s price, which had prompted angry condemnations from pregnant women, doctors and members of Congress.

More than 500,000 women give birth prematurely, and many of the babies don’t survive. Those who do are at an increased risk for many health problems, including mental retardation, cerebral palsy and autism.

For years, a form of the hormone progesterone known as 17P had been used to prevent preterm births. But the drug fell out of favor. Doctors and patients started using it again after a 2003 study, sponsored by the National Institutes of Health, showed that 17P could cut the risk of preterm births. Because no company marketed the drug, women obtained it cheaply from pharmacies that produce individual batches of drugs for patients.

But doctors and regulators had long worried about the purity and consistency of the compounded drug and were pleased when KV won FDA approval in February. The approval gave the company seven years of exclusive rights, and KV immediately sent letters to compounding pharmacies warning that they could no longer sell their versions.

Because the drug must be given for about 20 weeks, Makena would cost about $30,000 for each at-risk pregnancy, which could add more than $4 billion to the nation’s health-care bill.

KV has defended Makena’s price, saying the company had spent more than $200 million to develop the drug. In addition, KV started a program to help women who could not afford the drug.

In Friday’s announcement, KV said it is taking several steps to expand that program, including offering “supplemental rebates” that, “in conjunction with the list price reduction and the standard Medicaid rebate of 23.1 percent, will result in a substantially reduced cost per injection for state Medicaid agencies compared to list price.” The program will also remove income caps to qualify for financial assistance that will result in “85 percent of patients paying $20 or less per injection,” the company said.