Short women are twice as likely to have a premature baby then taller mothers, a new international study has found.
The chance of having a premature baby increases as the mothers height decreases, collaborators from the Liggins Institute based at the University of Auckland and Upsala University says.
Among mothers who were 155cm tall, or shorter, 9.4 percent of babies were born prematurely -- at less than 37 weeks of gestation -- and 1.1 percent were very premature, born less than 32 weeks of gestation.
But for mothers 179cm or taller, the figures rested at 4.7 percent and 0.5 percent respectively.
The research used data collected between 1991 and 2009, on more than 192,000 Swedish women aged over 18.
Premature birth is a significant cause of newborn death internationally, and has been linked to serious health problems in the long or short term, the study says.
In New Zealand in 2014, 7.4 percent of babies were born premature, with 1.3 percent at less than 32 weeks of gestation.
"Around half of all premature births are 'spontaneous', apparently with complex and often unknown causes," says study lead Dr Jose Derraik.
He says many studies show the mother's height may play a role.
"What complicates the picture is that there are probably a number of factors involved, such as the mother's ethnicity and their level of affluence."
However, researches are unsure of the reason behind this link between height and premature birth.
Dr Derraik has one suggestion.
"Short mothers tend to have less space for the babies to grow before birth, and this seems to lead to premature delivery in some women."
He says based on "mounting evidence", maternal height needs to be taken into account when evaluating the risk of a woman delivering a premature baby.