Bibi had a 10-month old daughter and was seven months pregnant when she was killed.
Relatives slit the throat of a young mother who was pregnant with her second child after she married against their will in eastern Pakistan, officials said on Friday, the latest in a spate of so-called "honour killings".
Muqaddas Bibi, 22, married Taufiq Ahmed three years ago in defiance of her family, who considered a marriage for love - rather than an arranged marriage - shameful, police investigator Mohammad Arshad told AFP.
Bibi's ties with her family were severed after the marriage, Arshad said, but her mother and brother allegedly approached her at a clinic where she was having a check-up on Thursday and convinced her to come home, saying they accepted her decision.
Local police station chief Gohar Abbas said that when Bibi reached her parents' house, her father, brother and mother cut her throat with a knife and she died on the spot.
Bibi had a 10-month old daughter and was seven months pregnant when she was killed, he added.
Abbas said that her family fled from their house after the murder in the village of Buttaranwali, some 75 kilometres (46 miles) north of Punjab provincial capital Lahore.
Police are hunting for them and have already detained another relative for inciting the killing, he said.
Last week sixteen-year-old Zeenat Bibi was killed in Lahore by her mother for marrying a man of her own choice in a case that sparked condemnation throughout the country.
It was swiftly followed by another killing, of a couple in Lahore who married without their family's consent.
On Sunday a young girl was killed by her brother for insisting on marrying the man of her choice in the city of Sialkot, also in Punjab.
A film on honour killings in Pakistan won an Oscar for best documentary short in February.
Prime Minister Nawaz Sharif vowed to eradicate the "evil" amid publicity for the film, "A Girl in the River: The Price of Forgiveness", but as yet no fresh legislation has been tabled.