The twins were delivered at almost 36 weeks' gestation

At the time of their birth, Ms Cohen was 59 -- which meant she was then the oldest woman in the US to give birth to twins.

Managing a pregnancy in a woman of Ms Birnbaum's age was uncharted territory, said Dr Abdulla Al-Khan, an obstetrician at Hackensack.

The twins were delivered at almost 36 weeks' gestation, and are expected to stay in the hospital for three days.

Ms Birnbaum underwent in-vitro fertilisation last year in Cape Town, South Africa. She said she wanted her youngest son, Ari, to have siblings closer to his age.

The oldest woman to give birth to twins is Carmen Bousada Lara, a Spanish woman who had twin boys last December, a week shy of her 67th birthday.