A Japanese research team has succeeded in impregnating a monkey that was given the extracted uterus of another primate in a transplant operation last year.

The researchers said Sunday that they hope the method can be used to enable pregnancies in women who are sick, do not have a uterus or cannot have children. No human uterus transplants have taken place in Japan, but 11 women have given birth following such procedures overseas.

According to the team, which includes researchers from Keio University, a crab-eating monkey had its uterus replaced with the uterus of another crab-eating monkey in January last year.

After resuming its menstrual cycle, the first monkey then received a fertilized egg and sperm created in April. The primate was found to be pregnant this month.

Before this operation, the team had succeeded in impregnating a crab-eating monkey after removing and reimplanting its uterus, and it later gave birth. But this is the first time a uterus has been transplanted from a different monkey.

Nationwide, 60,000 to 70,000 women have lost their uterus due to cancer treatment or pre-existing health conditions.

Despite the latest breakthrough, critics have raised ethical questions and safety concerns about uterus transplants, given that the uterus is not a life-sustaining organ.

The findings were presented at a meeting of the Japan Society of Obstetrics and Gynecology in Sendai.