The Federal Tort Claims Act provides a limited waiver of of federal sovereign immunity for certain claims, among them, negligence in the provision of medical services by health care providers at certain federal health care facilities (i.e. for certain medical malpractice cases).
A claim for medical malpractice asserts that a health care provider failed to use reasonable care in a manner consistent with care that a reasonable ordinary practitioners of the type of medical profession in which they performed their services should perform, causing harm to a patient.
What constitutes reasonable care for a medical practitioner is judged in the context of the law that applies to the place where the medical practitioner is practicing their profession.
Usually, that standard of care is governed by state law, and a failure to provide medical care that is illegal under state law will generally not constitute medical malpractice. In particular, the Assimilative Crimes Act, 18 U.S.C. § 13, makes state law crimes applicable to conduct occurring on lands reserved or acquired by the Federal government as provided in 18 U.S.C. § 7(3), when the act or omission is not made punishable by an enactment of Congress, by incorporating those crimes by reference into federal law as federal crimes.
So, a state law criminalizing abortion in a state where a federal facility is located would also be a federal crime which would be enforceable by federal prosecutors and would cabin the standard of care for health care in a state, unless the Department of Justice clearly stated an express policy not to enforce that statute. There are nuances to how the Assimilative Crimes Act applies, however, which are discussed at the link and it does not incorporate by reference state regulatory schemes.
Thus, while federal medical facilities can be immune to the restrictions of state law pursuant to the Property Clause of the U.S. Constitution, in practice, this is usually not the case (at least in substance). So, as a general rule, failing to perform medical services that are illegal in the state where the medical services are provided will not constitute medical malpractice. The federal government, by statute, regulation, or a binding opinion of the Department of Justice, can abrogate state law for the conduct of medical practitioners at a federal facility, but this is the exception rather than the rule.
I am not aware of instances of the federal government asserting this authority to authorize abortion procedures at a federal facility, although I acknowledge that I am not all knowing and that there may be some specific case where this has been done of which I am not aware. In part, this hasn't been done, because before Roe v. Wade was overturned by the recent Dobbs decision of the U.S. Supreme Court, it wasn't necessary to do so.
The federal government has the power to adopt its own laws regarding the legality of abortion procedures in its own health care facilities that would pre-empt state law. But, by and large, it has not done so. Indeed, in most circumstances there is a ban on using federal funds for health care involving abortion except to save the life of the mother, under the Hyde Amendment. This means that the vast majority of abortion procedures have to be performed outside federal health care facilities (although a more in depth analysis must be undertaken in circumstances like a foreign military base where there are no alternative sources of health care for a patient).
The exact parameters of the "health of the mother situation", the policies of the federal health care facility, the parameters of the state law abortion restrictions, and the nature of the patient's relationship to the facility (inmates are entitled to bring medical malpractice suits only in much more limited circumstances than other patients), would all be relevant in the analysis of whether an FTCA claim for medical malpractice in a case where a physician at a federal health care facility refused to provide abortion services necessary to protect the life of the mother.