The US Air Force said the mother began to have complications while the aircraft was at its flight altitude, typically above 28,000 feet (8,534 meters), due to the lower air pressure in the plane.
“The aircraft commander decided to descend in altitude to increase air pressure in the aircraft, which helped stabilize and save the mother’s life,” said the tweet, which was sent from the US Air Mobility Command’s official account.
Once the plane was on the ground at the Ramstein base, personnel from the Air Force’s 86th Medical Group assisted in the delivery of the baby in the C-17’s cargo bay, the tweet said. Mother and baby were then transported to a nearby medical facility where they are in good condition.
Ramstein Air Base has emerged as a key transit point for evacuees from Afghanistan.
Gen. Hank Taylor told reporters during a briefing at the Pentagon on Saturday that C-17s were moving evacuees from an air base in Qatar to Germany to relieve a backlog of people at the Qatar base, where many flights coming directly from Kabul have been terminating.
On Friday, US military evacuation flights from the Afghan capital were paused for almost eight hours because the staging area at the US military base in Qatar was full, officials said.
Brig. Gen. Josh Olson told CNN on Saturday that the Ramstein base has a capacity for 5,000 people, but extra facilities under construction should accommodate 7,500 by Sunday evening.
Olson said he expects evacuees to stay for between 48 and 72 hours at the base. The US agreement with Germany states they should not stay for more than 10 days, he added.
Since the end of July, 22,000 people have been evacuated, Gen. Taylor said. Of those, 17,000 have been evacuated since August 14.
On Friday, the Air Force said one of its C-17 flights from Afghanistan had set a record for the number of people ever carried aboard the aircraft.
A flight on August 15 that the Air Force originally said carried 640 people actually had 823 aboard, Air Mobility Command said in a tweet, after the initial count did not included 183 children aboard the aircraft.
CNN’s Atika Shubert and Ellie Kaufman contributed to this report.