Customs and Border Protection officials ordered a pregnant Chinese tourist to return to Shanghai early Monday morning after she had arrived in Saipan in the Northern Marianas the previous day.
It is not known whether the woman had travelled to the CNMI to have her baby there.
There are concerns hundreds of pregnant Chinese tourists have travelled to Saipan in recent years to give birth there, reportedly so the child would automatically qualify for U.S. citizenship.
Last Thursday, the CNMI delegate to the US Congress, Gregorio Kilili Sablan, warned that birth tourism could risk the U.S. visa waiver programme for tourists from China and Russia.
In 2009, the Department of Homeland Security granted U.S. visa waivers for both countries allowing tourists to enter and stay in the CNMI for up to 45 days without needing a U.S. visa.