"She is supposed to deliver in a few days, but this is her first visit to a health centre," said Nazia Hemat, an obstetrician at Mia Abdul Hakim Hospital in the southern province of Kandahar.
Rabia is fortunate in being able to visit the hospital: "Men often don't allow their pregnant women to go to hospitals and doctors," Ranna Tarin, director of Kandahar women's affairs department, told IRIN.
"We know young women die during pregnancy and at childbirth but we don't know how many," said Shamsuddin Tanwer, an official of the Afghan Independent Human Rights Commission (AIHRC) in Kandahar, the country's second largest city.
Afghan law sets 16 as the minimum age of marriage for a girl and 18 for a boy, but many are married at a younger age and without the genuine consent of those concerned.
According to AIHRC, 60-80 percent of all marriages are forced and/or under-age marriages.
Rabia's mother, Amina, said they married their daughter at an early age because "everybody and all parents do the same," and that "it is not good to keep a daughter at home for long; it's better she goes to her husband's home as soon as possible."
Poverty, illiteracy and lack of awareness about the dangers of early marriage are other major reasons why parents marry off their girls at a young age, according to AIHRC.
"A lot of people do not know that early marriages pose serious health and psychological risks to young girls," said Razeqa Nezami, a human rights activist. "There is also a strong misunderstanding that marrying off a daughter as early as possible is in line with Islam," she said.
In the countryside there is little awareness of, or respect for, civil law and the minimum legal age for marriage. Some suggest the government should train imams and other religious leaders to ensure marriage laws are upheld when they formalize marriages.
"When a girl goes into marriage she actually undertakes the burden and responsibilities of an adult," Malalai Nazery, a maternal health officer with the UN Children's Fund (UNICEF) in Kabul, told IRIN. "Marriage can be an abnormal and risky trajectory for a child."
Afghanistan has the second highest fertility rate in the world at 6.51 percent. For every 1,000 women in the 15-19 age-range, 121 give birth to one or more children, according to UN Population Fund (UNFPA) estimates for 2005-10.Female life expectancy in Afghanistan is 44 - one of the lowest in the world.
Afghanistan also has among the worst maternal and infant mortality rates in the world. About 25,000 mothers die every year during pregnancy, at child birth or after delivery, according to UNFPA (equivalent to 800 deaths per 100,000 women).
"Mortality and morbidity figures among mothers aged 15-19 are much higher than for women older than 19," said UNICEF's Nazery, adding that young mothers often lack awareness of the risks of pregnancy and child delivery. "Child mothers and their children are usually weak and vulnerable to diseases."
Only 14 percent of births in Afghanistan are attended by skilled health workers, according to UNFPA.
Research by the German NGO Medica Mondiale in 2004 highlighted the negative effects of early marriages in Afghanistan: "It blocks [girls] from education and any possibility of independent work. It subjects them to pregnancy and childbirth before they have reached physical maturity," it said.