New York, Aug 20 (IANS): Researchers have found that preterm and early term delivery are independent risk factors for premature death in women upto 40 years later. According to the study, nearly 11 per cent of all deliveries worldwide occur preterm (before 37 weeks of pregnancy).

Women who deliver preterm or extremely preterm (22-27 weeks) have been reported to have increased risks of developing conditions such as heart disease or diabetes in later life, but little is known about their long-term risk of death.

For the findings, published in the journal The BMJ, the research team set out to examine the long term mortality linked to preterm delivery in women and to explore the potential influence of shared genetic or environmental factors within families.

"Women who deliver prematurely need long term clinical follow-up for detection and treatment of chronic disorders associated with early mortality," said study researcher Casey Crump from the Icahn School of Medicine at Mount Sinai in the US.

Using nationwide birth records, they analysed data on length of pregnancy for over two million women who gave birth in Sweden from 1973-2015. Deaths were then identified from the Swedish Death Register up to 31 December 2016 (a maximum follow-up time of 44 years). Overall, 76,535 (3.5 per cent) of women died, at an average age of 58.

The researchers found that women who delivered preterm or extremely preterm had 1.7-fold and 2.2-fold increased risk of death from any cause, respectively, during the next 10 years compared to those who delivered full term. This equates to around 28 excess deaths per 1,00,000 person-years.

Whereas risks were highest in the first 10 years after delivery and then declined, absolute differences in death associated with preterm delivery increased with longer follow-up times.

Overall, an estimated 2,654 excess deaths in this population were associated with preterm delivery (one excess death for every 73 women who delivered preterm). Several specific causes of death associated with preterm delivery were identified, including cardiovascular and respiratory disorders, diabetes, and cancer.

"What's more, these findings did not seem to be attributable to shared genetic or environmental factors within families," the author wrote. However, strengths included the large sample size and long follow-up time, prompting the researchers to say that premature delivery should now be recognised as a risk factor for early mortality in women that can remain raised up to 40 years later.