There's only been one female head of government in modern history who gave birth while in office

(CNN)New Zealand Prime Minister Jacinda Ardern isn't the first prime minister to expect a baby while in office.

A generation ago, Pakistani Prime Minister Benazir Bhutto was pregnant with, and gave birth, to her daughter Bakhtawar on January 25, 1990. At the time she'd been in office a little more than a year.
The first-ever female leader of a Muslim nation, Bhutto served as the prime minister of Pakistan from 1988 to 1990 and from 1993 to 1996. She was assassinated in 2007 during a political campaign
    On Friday, Bakhtawar, who's now a trustee at the Shaheed Zulfikar Ali Bhutto Institute of Science and Technology, passed along her congrats to the New Zealand leader "on the wonderful news."

    Then and now

    Ardern said she would be taking six weeks leave following the baby's birth. Deputy Prime Minister Winston Peters would serve as acting prime minister during that time.
    "I am not the first woman to multi-task, I'm not the first woman to work and have a baby," she said. "I know these are special circumstances but there will be many women who will have done this well before I have."
    Benazir Bhutto with Rajiv Gandhi on her right in Paris on July 13, 1989.
    The challenges were far more daunting for Bhutto 27 years ago.
    She was apprehensive that her rivals, who wanted an interim government in place while she was having a baby, wanted to push her aside. She went to a Karachi hospital "incognito" and had Bakhtawar via a Caesarian section, according to London's Independent newspaper.
    "The next day I was back on the job, reading government papers and signing government files," she later wrote.
    "Only later did I learn that I was the only head of government in recorded history actually to give birth while in office. It was a defining moment, especially for young women, proving that a woman could work and have a baby in the highest and most challenging leadership positions."
    Bhutto had two other children. Her first child, Bilawal Bhutto Zardari, was born months before her 1988 election. Another daughter, Aseefa, was born in 1993. That was a couple of months before she took office for her second stint as prime minister.
    Update: The headline of this piece has been updated to more accurately reflect Bhutto's tenure.