What is the impact of interventions that prevent fetal mortality on the increase of preterm live births in the State of Sao Paulo, Brazil?

Background: There is a global growing trend of preterm births and a decline trend of fetal deaths. Is there an impact of the decline of fetal mortality on the increase of preterm live births in State of Sao Paulo, Brazil?
Methods: The time trends were evaluated by gestational age through exponential regression analysis. Data analyzed included the fetal mortality ratio, proportion of preterm live births, fertility rate of women 35 years and over, prenatal care, mother's education, multiple births and cesarean section deliveries. A survival analysis was carried out for 2000 and 2010.
Results: Preterm births showed the highest annual increase (3.2%) in the less than 28 weeks of gestation group and fetal mortality ratio decreased (7.4%) in the same gestational age group. There was an increase of cesarean section births and it was higher in the < 28 weeks group (6.1%). There was a decreased annual trend of mothers with inadequate prenatal care (6.1%) and low education (8.8%) and an increased trend in multiple births and fertility rates of women of 35 years and over. The variables were highly correlated to which other over time. In 2000, 8.2% of all pregnancies resulted in preterm births (0.9% in fetal deaths and 7.3% in live births). In 2010, the preterm birth increased to 9.4% (0.8% were preterm fetal deaths and 8.6% preterm live births).
Conclusions: The results suggest that 45.2% could be the maximum contribution of successful interventions to prevent a fetal death on the increase in preterm live births. This increasing trend is also related to changes of the women reproductive profile with the change of the women reproductive profile and access to prenatal care.