Maternal risk factors and obstetric complications in late preterm prematurity.

Objective: Late preterm prematurity has been related to poorer neonatal outcomes. However, research has focused on the neonatal outcomes of late preterm infants, maternal characteristics of these births have been less evaluated. The aim of the study was to compare maternal risk factors and obstetric complications in late preterm births (LPTB) and term births. These factors were also assessed comparing spontaneous LPTB with medically-indicated LPTB.

Study Design: We conducted a retrospective cohort study with two groups. All singleton LPTB occurred at our University Hospital between January 1, 2009 and December 31, 2010 were included in the first cohort (n=171). A comparison cohort of term births was configured in a ratio 2:1 (n=342). Well-dated pregnancies without congenital malformations, congenital infections or chromosome abnormalities were eligible. LPTB were classified into two groups, spontaneous LPTB and medically-indicated LPTB following delivery indications. Statistical analysis of categorical variables was performed using either χ(2) or Fisher's exact. Continuous variables were compared using the Student's t-test.

Results: Women with LPTB had more medical conditions than women with term births (29% vs 15.7%; P=0.002). Prior preterm births (9.7% vs 2%; P<0.001), prior adverse obstetric outcomes (6.9% vs 2.3%; P<0.001), and obstetric complications were also more frequent in LPTB than in term births. However, no differences were found in maternal medical conditions when spontaneous LPTB and medically-indicated LPTB were compared. Women with medically-indicated LPTB were older (33.69 vs 31.07; P=0.003) and mainly nulliparous (75.8% vs 49.4%; P=0.002). Obstetric complications were more frequent in medically-indicated LPTB than in spontaneous LPTB.

Conclusions: Maternal risk factors and obstetric complications are significantly higher in LPTB than in term births. These factors should be considered to identify women at risk for either spontaneous or medically-indicated LPTB.