 In April 2019, Gillibrand signed a letter led by Catherine Cortez Masto to Immigrations and Customs Enforcement and Customs and Border Enforcement asserting that "the civil detention of an expectant mother for potential immigration offenses is never justified" due to the "absence of compelling evidence that the detention of a pregnant woman is necessary because she is a threat to herself or others, or is a threat to public safety or national security".The senators requested the CBP enact measures that would ensure "timely and appropriate treatment" for pregnant women in custody along with both agencies providing information on how available facilities and doctors are for pregnant immigrants and complete data on the number of those currently in custody.In April 2019, Gillibrand was one of six Democratic senators to sign a letter to Acting Defense Secretary Patrick M. Shanahan expressing concern over memos by Marine Corps Gen. Robert Neller in which Neller critiqued deployments to the southern border and funding transfers under President Trump's national emergency declaration as having posed an "unacceptable risk to Marine Corps combat readiness and solvency" and noted that other military officials had recently stated that troop deployment did not affect readiness.