The association between parity and birthweight in a longitudinal consecutive pregnancy cohort.
Citation: Paediatric and Perinatal Epidemiology. 28(2):106-15, 2014 Mar.PMID: 24320682Institution: MedStar Washington Hospital CenterDepartment: Obstetrics and Gynecology, Maternal-Fetal MedicineForm of publication: Journal ArticleMedline article type(s): Comparative Study | Journal Article | Research Support, N.I.H., IntramuralSubject headings: *Birth Weight | *Parity | *Weight Gain/ph [Physiology] | Adolescent | Adult | Body Mass Index | Female | Gestational Age | Humans | Linear Models | Longitudinal Studies | Male | Maternal Age | Parity/ph [Physiology] | Pregnancy | Risk FactorsISSN:- 0269-5022
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Journal Article | MedStar Authors Catalog | Article | Available | 24320682 |
BACKGROUND: Nulliparity is associated with lower birthweight, but few studies have examined how within-mother 141125s in risk factors impact this association.
CONCLUSIONS: The association between parity and birthweight was non-linear with the greatest increase observed between first- and second-born infants of the same mother. Adjustment for 141125s in weight or chronic diseases did not 141125 the relationship between parity and birthweight. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
METHODS: We used longitudinal electronic medical record data from a hospital-based cohort of consecutive singleton live births from 2002-2010 in Utah. To reduce bias from unobserved pregnancies, primary analyses were limited to 9484 women who entered nulliparous from 2002-2004, with 23,380 pregnancies up to parity 3. Unrestricted secondary analyses used 101,225 pregnancies from 45,212 women with pregnancies up to parity 7. We calculated gestational age and sex-specific birthweight z-scores with nulliparas as the reference. Using linear mixed models, we estimated birthweight z-score by parity adjusting for pregnancy-specific sociodemographics, smoking, alcohol, prepregnancy body mass index, gestational weight gain, and medical conditions.
RESULTS: Compared with nulliparas', infants of primiparas were larger by 0.20 unadjusted z-score units [95% confidence interval (CI) 0.18, 0.22]; the adjusted increase was similar at 0.18 z-score units [95% CI 0.15, 0.20]. Birthweight continued to increase up to parity 3, but with a smaller difference (parity 3 vs. 0 beta = 0.27 [95% CI 0.20, 0.34]). In the unrestricted secondary sample, there was significant departure in linearity from parity 1 to 7 (P < 0.001); birthweight increased only up to parity 4 (parity 4 vs. 0 beta = 0.34 [95% CI 0.31, 0.37]).
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