title: Body Mass Index Change between Pregnancies and Risk of Spontaneous Preterm Birth.
abstract: Objective Studies have reported an increased risk of spontaneous preterm birth associated with elevated prepregnancy body mass index (BMI) among nulliparous but not multiparous women. We examined whether changes in BMI and weight between pregnancies contributed to risk of preterm birth among obese (BMI > 29 kg/m(2)) women. Study Design This study utilized maternally linked California birth records of sequential singleton births between 2007 and 2010. Preterm birth was defined as 20 to 31 or 32 to 36 weeks of gestation. BMI was examined as category change and by tertile of weight change. Primary analyses included women without diabetes or hypertensive disorders; these women were compared with those without prior preterm birth, women with preterm deliveries preceded by spontaneous preterm labor, and women without any exclusions (i.e., diabetes or hypertensive disorders). Results Analyses showed that obesity was not associated with increased risk of spontaneous preterm birth among multiparous women. Women whose BMI increased had a decreased risk of spontaneous preterm birth at 32 to 36 weeks. Change in BMI or weight between pregnancies did not substantively alter results. Conclusion Among multiparous women, obesity was associated with reduced risk of spontaneous preterm delivery. This observed association is complex and may be influenced by maternal age, gestational age, placental insufficiency, and altered immune response.
authors.affiliation: Division of Neonatal and Developmental Medicine, Department of Pediatrics, Stanford University, Stanford, California.
authors.forename: K L
authors.initials: KL
authors.lastname: Riley
authors.affiliation: Division of Neonatal and Developmental Medicine, Department of Pediatrics, Stanford University, Stanford, California.
authors.forename: S L
authors.initials: SL
authors.lastname: Carmichael
authors.affiliation: Division of Neonatal and Developmental Medicine, Department of Pediatrics, Stanford University, Stanford, California.
authors.forename: J A
authors.initials: JA
authors.lastname: Mayo
authors.affiliation: Division of Neonatal and Developmental Medicine, Department of Pediatrics, Stanford University, Stanford, California.
authors.forename: B Z
authors.initials: BZ
authors.lastname: Shachar
authors.affiliation: Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Stanford University, Stanford, California.
authors.forename: A I
authors.initials: AI
authors.lastname: Girsen
authors.affiliation: Division of Neonatal and Developmental Medicine, Department of Pediatrics, Stanford University, Stanford, California.
authors.forename: M B
authors.initials: MB
authors.lastname: Wallenstein
authors.affiliation: Division of Neonatal and Developmental Medicine, Department of Pediatrics, Stanford University, Stanford, California.
authors.forename: J B
authors.initials: JB
authors.lastname: Gould
authors.affiliation: Division of Neonatal and Developmental Medicine, Department of Pediatrics, Stanford University, Stanford, California.
authors.forename: D K
authors.initials: DK
authors.lastname: Stevenson
authors.affiliation: Division of Neonatal and Developmental Medicine, Department of Pediatrics, Stanford University, Stanford, California.
authors.forename: G M
authors.initials: GM
authors.lastname: Shaw
mesh_terms: D000328:Adult; D015992:Body Mass Index; D002140:California / Q000453:epidemiology; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D009765:Obesity / Q000150:complications* / Q000453:epidemiology*; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology* / Q000209:etiology; D012044:Regression Analysis; D012307:Risk Factors; D015430:Weight Gain; D055815:Young Adult