Her grandmother brought her a pregnancy test kit after she missed her period.
Local media in Vietnam have reported yet another case of child sex abuse involving a 10-year-old girl in the Mekong Delta.
Local police said the family of the girl, only identified as H., filed a complaint this week after an ultrasound scan found that she was four weeks pregnant.
A Thanh Nien report cited H’s grandmother as saying that H usually spent time alone at home as her parents worked far away.
H lives with her grandfather, who also works outside most of the day.
The grandmother said H had called her on Monday to tell her she had missed her period. She immediately took a bus home and bought her a pregnancy kit, which tested positive.
The grandmother said it took some time for H to admit a 38-year-old neighbor had raped her on numerous occasions.
Having sex with a child under 13 years of age in Vietnam is ruled as child rape, and is punishable by death.
In Vietnam, more than 8,200 cases of child abuse came to light between 2011 and 2015, including 5,300 cases of sexual abuse, according to official figures released a year ago.
In most cases, the perpetrators were people familiar with the children, such as teachers, school security officials, relatives and neighbors.
This month alone, Vietnamese police have arrested two suspects: a 76-year-old accused of molesting seven girls at an apartment building in the southern beach town of Vung Tau, and a 34-year-old Hanoian accused of assaulting his 8-year-old neighbor.
Experts said at a recent conference that sexual abuse cases in Vietnam tend to be prolonged or even buried due to legal loopholes that require evidence of serious physical effects on the victims.