Abstract
The association of body mass index (BMI) and gestational weight gain (GWG) with preterm birth (PTB) remains controversial in the literature. To evaluate different maternal BMI and GWG categories, according to the initial BMI, in relation to different PTB subtypes and perinatal outcomes, we conducted a secondary analysis of a multicentre cross-sectional study, along with a nested case-control study including PTB from 20 centers in Brazil. Pre-pregnancy underweight was associated with a lower risk of provider-initiated PTB, while overweight and obesity were associated with a higher risk of provider-initiated PTB and a lower risk of spontaneous preterm birth. Insufficient gestational weight gain was associated with a higher prevalence of spontaneous PTB and preterm premature rupture of membranes. Excessive GWG correlated with a higher prevalence of provider-initiated PTB or preterm premature rupture of membranes. Irrespective of the initial BMI, the greater the rate of GWG, the higher the predicted probability of all PTB subtypes, except for spontaneous PTB in underweight women and those with normal BMI. On multivariate analysis, the initial BMI was shown to be the only factor associated with pi-PTB. Briefly, further studies evaluating the risk for PTB should consider that GWG may have a different role depending on the initial BMI and PTB subtype.
Highlights
Preterm birth (PTB) is an increasing health concern, as well as a major cause of neonatal mortality and long-term morbidity worldwide[1]
Overweight and obesity were associated with a higher risk of pi-preterm birth (PTB), despite a lower risk of spontaneous preterm birth (sPTB)
Underweight was associated with a 40% lower risk for pi-PTB
Summary
Preterm birth (PTB) is an increasing health concern, as well as a major cause of neonatal mortality and long-term morbidity worldwide[1]. Body mass index (BMI) before and during early pregnancy and gestational weight gain (GWG) during pregnancy have already been associated with preterm birth. With different contexts, such as racial, cultural, and socioeconomic factors, compared to low and middle-income countries[7,8,9] These studies have generally failed to distinguish between different preterm birth subtypes (sPTB, PROM-PTB and pi-PTB) and the rate of gestational weight gain, limiting their ability to delineate the dose-response relationship between gestational weight gain and preterm birth subtype[10,11,12]. BMI and gestational weight gain in early pregnancy should still be evaluated, in association with preterm births and perinatal outcomes, regarding the rate of gestational weight gain as a modifying factor for adverse maternal and perinatal outcomes in the developing world[13]
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