Second Lady Usha Vance nearly took a tumble while stepping off a helicopter Monday ... with Vice President JD Vance just a few seconds behind her.

Usha was carrying their baby, Alec, as she made her way down the aircraft steps and appeared to lose her footing near the bottom.

She caught herself and kept moving ... with the baby still safely strapped to her person.

JD then emerged moments later and came down the same steps with daughter Mirabel without any issue.

As TMZ previously reported, JD and Usha welcomed Alec Neel Vance in July -- their fourth child and the first baby born to a sitting U.S. vice president in more than 150 years.

Alec joined older the siblings of the Second Family -- Ewan, Vivek and Mirabel.

Thankfully ... Usha managed to stick the landing with the Vance's newest edition.