Researchers at Akershus University Hospital made their findings after monitoring 2,206 pregnant women who planned to have natural births, medical news site Dagens Medisin reports.

The researchers tracked the women from the 32nd week of their pregnancies right up until they gave birth.

Some 7.5 percent of the respondents, who each filled out a detailed questionnaire, were found to fear giving birth. The study found that these women took an average of one hour and 32 minutes longer to give birth than the other budding mothers.     

Mums gripped by the fear factor spent an average of eight hours in labour, compared to six hours and 28 minutes for women who scored below 85 on the Wijma Delivery Expectancy Questionnaire.

“We reasoned that birth anxiety can affect the length of the birth in two different ways,” study co-author Samantha Salvesen Adams told Dagens Medisin.

“Birth anxiety can increase stress hormone levels. During the birth, an elevated stress hormone level can reduce contraction frequency, thereby delaying the birth.

“In addition, or alternatively, we believe that anxiety during a birth can affect communication between the woman giving birth and healthcare personnel, with possible consequences for the childbirth process,” said Adams.

Just over half of the women were first-time mothers, while the average age of participants was 30.9 years.

The study was first published last week in BJOG: An International Journal of Obstetrics & Gynaecology.