The incident happened as the couple reached the court premises to record Farzana's statement to defend her husband against allegations by her family that he kidnapped her and forced her to marry him.
Initially, the family members fired shots in the air and tried to snatch her from Iqbal.
After failing in their attempt, nearly 20 members of her family, including her father and brothers, attacked the couple with sticks and bricks before a crowd of onlookers in front of the high court of Lahore, said police official Naseem Butt.
Farzana, who was three-months pregnant, died while her husband managed to escape.
Police arrested Farzana's father but her brothers fled from the scene, The News International reported.
Police on information reaching the spot sent the body for autopsy and registered a case on complaint of the victim's husband.
Around 900 women were killed in Pakistan last by their families in honour killings, according to Human Rights Commission of Pakistan, a private organisation.