New research has found links between Human Papilloma Virus (HPV), placentas and pregnancy complications.
The research conducted by the University of Otago and published in the US Journal of Modern Pathology studied 339 placentas between 2009 and 2014, and found three quarters of them were infected with HPV.
The study found mothers with an infected placenta gave birth on average a week early, and 15 percent of the infected placentas were associated with lower birth weight.
Of the infected placentas, 78 percent were classed as high risk, which is known to cause cervical and other cancers.
Head of the study Dr Noelyn Hung said three different patterns of the infection were found in the placentas.
"Not every infected placenta will have problems, it depends on the pattern of infection which is influenced by the mother's immune system."
Dr Hung said while further investigation is required, the study provides evidence to support HPV vaccination.
The Ministry of Health provides HPV immunisation free to girls and young women up to the age of 20.
The immunization aims to protect young women from HPV infection and the risk of developing cervical cancer.
Currently around 150 women are diagnosed with cervical cancer and 50 women die from it each year in New Zealand.
Dr Hung said the vaccine immunises against four strands of HPV but there are over 180 strands of the virus.
"We still don't know if the vaccine which is targeting HPV in the cervix will help with infection in the placenta, we can hope, but we have no evidence of that yet," she said.