Child marriage threatens the health and life of girls. Complications from pregnancy and childbirth are the main cause of death among adolescent girls below age 19 in developing countries. Pregnant girls aged 15 to 19 are twice as likely to die in childbirth as women in their 20s, and girls under the age of 15 are five to seven times more likely to die during childbirth. These consequences are due largely to girls' physical immaturity where the pelvis and birth canal are not fully developed. Teen pregnancy, particularly below age 15, increases risk of developing , since their smaller pelvises make them prone to obstructed labor. Girls who give birth before the age of 15 have an 88% risk of developing fistula. Fistula leaves its victims with urine or fecal incontinence that causes lifelong complications with infection and pain. Unless surgically repaired, obstetric fistulas can cause years of permanent disability, shame to mothers, and can result in being shunned by the community. Married girls also have an increased risk of , , and than non-married peers or girls who marry in their 20s.
The was passed during the tenure of British rule on . It forbade the marriage of a male younger than 21 or a female younger than 18 for Hindus, Buddhists, Christians and most people of India. However, this law did not and currently does not apply to India's 165 million Muslim population, and only applies to India's Hindu, Christian, Jain, Sikh and other religious minorities. This link of law and religion was formalized by the British colonial rule with the Muslim personal laws codified in the Indian Muslim Personal Law () Application Act of 1937. The age at which India's Muslim girls can legally marry, according to this , is 9, and can be lower if her guardian () decides she is sexually mature. Over the last 25 years, All India Muslim Personal Law Board and other Muslim civil organizations have actively opposed India-wide laws and enforcement action against child marriages; they have argued that Indian Muslim families have a religious right to marry a girl aged 15 or even 12. Several states of India claim specially high child marriage rates in their Muslim and tribal communities. India, with a population of over 1.2 billion, has the world's highest total number of child marriages. It is a significant social issue. As of 2016, the situation has been rectified by .
Child marriage has lasting consequences on girls, from their health, education and social development perspectives. These consequences last well beyond adolescence. One of the most common causes of death for girls aged 15 to 19 in developing countries was pregnancy and child birth. In , which is estimated as having the highest rate of child marriage in the world, about 3 in 4 girls marry before their 18th birthday.