“It will also defend American taxpayers from having their hard-earned dollars siphoned away to finance the direct and downstream costs associated with birth tourism,” Ms. Grisham said. “The integrity of American citizenship must be protected.”

As his impeachment trial in the Senate begins and his re-election campaign heats up, Mr. Trump has indicated that he intends to highlight his administration’s efforts to restrict immigration. He is also expected to expand his 2017 travel ban to several new countries — including Belarus, Myanmar, Eritrea, Kyrgyzstan, Nigeria, Sudan and Tanzania — as early as Monday to mark the anniversary of the current restrictions on eight nations.

The birth tourism rule raises the burden of proof for pregnant women by outlining in writing that giving birth in the country “is an impermissible basis” for visiting the United States. Even if a woman says she is entering the country for medical treatment — a legitimate factor for visa eligibility — she will need to satisfy visa officers that she has enough money to pay for such treatments. She will also need to prove that the medical care she is seeking was not available in her home country.

“If an applicant’s responses to this line of questions are not credible, that may give consular officers reason to question whether the applicant qualifies for a visa,” Mr. Risch said in the rule.

Kerri Talbot, the director of federal advocacy for Immigration Hub, an immigrants’ rights group, criticized the State Department for not specifying how officers abroad would determine if a traveler was pregnant.

“It is absurd that the Trump administration is turning embassy employees into reproductive policemen,” Ms. Talbot said.

The new policy does not change guidance for airport officers working for the Department of Homeland Security, meaning visa eligibility changes would occur outside the United States, not at airport immigration counters. The rule also does not effect those visiting from the 39 countries that qualify for the Visa Waiver Program, which allows citizens of those countries to visit the United States for short periods without visas.