Objective:

To analyze obstetric variables associated with the birth of moderate and late premature babies in a city in the southern region of Brazil.

Method:

Cross-sectional study that analyzed the obstetric variables of 151 moderate and late preterm infants from May 2016 to May 2017 resident in Santa Maria/RS. Data were collected by means of their own instrument daily, and subsequently analyzed descriptively and by comparison of frequency and correlation.

Results:

Twinning (14.6%) was the most frequent feature among late twins when compared to the moderate group (p = 0.019). The other factors showed no significant difference. The higher number of previous premature births has a significant correlation with the lower gestational age at birth (CI = -0.522, p = 0.008).

Conclusion:

For the two groups of premature infants studied, the reasons did not present significant difference, which suggests homogeneity regarding the obstetric reasons for early birth.

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