The Growing Trend of Moderate Preterm Births: An Ecological Study in One Region of Brazil

BACKGROUND: Preterm birth is a serious public health problem, as it is linked to high rates of neonatal and child morbidity and mortality, with Brazil listed among the countries with the ten highest numbers of premature births. Nonetheless, knowledge is scarce regarding prematurity and associated factors in mid-sized cities. The objective of this study was to analyze the trend of preterm births and associated factors in a municipality located in the state of Paraná, Brazil. METHODS: This was an ecological time series study of births recorded into the Live Birth Information System for residents of Maringá, Paraná, Brazil, between 2000 and 2013. The polynomial regression model was used for trend analysis of preterm birth, characteristics of the mother, gestation and delivery, and newborn. The association with preterm birth was analyzed using odds ratio (OR). RESULTS: A total of 61,634 live births were analyzed, of which 5,632 were preterm births. Prematurity increased from 7.9% in 2000 to 11.2% in 2013 –an average increase of 0.54% per year (r(2) = 0.93)–with a growing share of moderate preterm births (32 to <37 weeks), which rose from 7.0% in 2000 to 9.7% in 2013. Between 2011 and 2013, multiple pregnancy (OR = 16.64; CI = 13.24–20.92), inadequate number of prenatal visits (OR = 2.81; CI = 2.51–3.15), Apgar score below 7 at 1 (OR = 4.07; CI = 3.55–4.67) and 5 minutes (OR = 10.88; CI = 7.71–15.36), low birth weight (OR = 38.75; CI = 33.72–44.55) and congenital malformations (OR = 3.18; CI = 2.14–4.74) were associated with preterm birth. A growing trend was observed for multiple pregnancies, with an average annual increase of 0.32% (r(2) = 0.90), as well as for C-section birth (2.38% yearly increase). Of all newborn characteristics, Apgar score below 7 at 5 minutes (-0.19% per year) and low birth weight (-1.43%) decreased, whereas congenital malformations rose (0.20% per year). CONCLUSIONS: Efforts are required to prevent premature delivery, particularly during the moderate period, as well as greater care during the prenatal period towards expectant mothers bearing multiple pregnancies, birth defects, in addition to reducing C-section birth as it may be linked to preterm birth.