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Premature/preterm birth

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Premature/Preterm Birth

Sex and Gender-based Analysis of this topic

Premature or preterm birth is defined as birth occurring between 20 and 37 weeks of gestation and is typically expressed as a proportion of total live births for a given location and time range.  Although medical advances have greatly increased survival rates, preterm birth is still the most important cause of perinatal mortality and morbidity [1]. Preterm birth accounts for 75-85% of all perinatal mortality (stillbirths and deaths to infants less than 7 days old) in Canada [2]. Preterm birth is also associated with elevated risks for cerebral palsy, as well as other long term health consequences [3]. The rate of premature birth in Canada has gradually increased from 1981 until 2000 to 7.6 [4-5]. The rate of preterm birth in British Columbia is slightly above the Canadian average and continues to increase; in 2000/2001 it was 8% and in 2005/2006 it was 9.7% [6]. A large portion of this increase can be attributed to an increased use of obstetrical intervention, as well as an increasing rate of multiple births in recent years, which carries a higher risk for premature delivery [7].

Sex Issues
Preterm birth rates are affected by a number of maternal factors including race, single marital status, younger or older maternal age, low or high weight gain, previous preterm delivery, smoking [8], low pre-pregnancy weight, infection, stress [9], and multiple pregnancies [10]. Preterm birth is often associated with low birth weight, which is in turn associated with developmental delay, risk of mortality, longer lengths of stay in hospital, and other long-term health effects [11].  Though single births are responsible for 80% of all preterm births in Canada, rates of preterm birth are much higher among twins and other higher multiple births [12]. The rate of multiple births has been increasing for decades and recently has begun to rise much more quickly [13], increasing the risk for preterm births.

Gender Issues

Many of the above maternal factors influencing rates of preterm birth have strong societal and gender components. Older maternal age, for example, is most likely a result of women entering the workforce and delaying the decision to have children. As well, the rise in the rate of multiple births is likely attributable to infertility treatments and while these technologies provide positive benefits, the rate of preterm births and associated dangers with some of these treatments are rising accordingly [14].


The rate of preterm birth varies greatly across Canada. In Prince Edward Island, the rate of preterm birth is almost 6%, while in Nunavut the rate is 10%. Differences in preterm birth rates have also been demonstrated for Status Indians in British Columbia and Manitoba [15-16]. In British Columbia from 1995-2004, the rate of preterm birth for Status Indians was consistently higher, peaking in 2004 at 11% as compared to 7% for the rest of the population [17]. 

There has also been recent investigation into the relationship between low socioeconomic status and elevated preterm birth rates. A study in Toronto found that having low socioeconomic status increased the chances of preterm birth, low birth weight, and full-term low birth weight [18].


The gradual rise in preterm birth rates across Canada points to changing situations for mothers. Technological advances such as refined ultrasounds and infertility drugs are creating positive results in perinatal mortality and fertility but at the same time increasing the rate of preterm birth. Further study is also needed to examine the causes for the elevated rate of preterm birth for Status Indians and those with low socioeconomic status.