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Heightened risk of preterm birth and growth restriction after a first-born son.

CPQCC Publication
TitleHeightened risk of preterm birth and growth restriction after a first-born son.
Publication TypeJournal Article
Year of Publication2015
AuthorsBruckner TA, Mayo JA, Gould JB, Stevenson DK, Lewis DB, Shaw GM, Carmichael SL
JournalAnn Epidemiol
Date Published2015 Oct
KeywordsAfrican Americans, Birth Order, Birth Weight, California, Ethnic Groups, European Continental Ancestry Group, Family Characteristics, Female, Gestational Age, Hispanic Americans, Humans, Indians, North American, Infant, Newborn, Linear Models, Male, Pregnancy, Pregnancy Outcome, Premature Birth, Proportional Hazards Models, Sex Factors, Siblings

PURPOSE: In Scandinavia, delivery of a first-born son elevates the risk of preterm delivery and intrauterine growth restriction of the next-born infant. External validity of these results remains unclear. We test this hypothesis for preterm delivery and growth restriction using the linked California birth cohort file. We examined the hypothesis separately by race and/or ethnicity.

METHODS: We retrieved data on 2,852,976 births to 1,426,488 mothers with at least two live births. Our within-mother tests applied Cox proportional hazards (preterm delivery, defined as less than 37 weeks gestation) and linear regression models (birth weight for gestational age percentiles).

RESULTS: For non-Hispanic whites, Hispanics, Asians, and American Indian and/or Alaska Natives, analyses indicate heightened risk of preterm delivery and growth restriction after a first-born male. The race-specific hazard ratios for preterm delivery range from 1.07 to 1.18. Regression coefficients for birth weight for gestational age percentile range from -0.73 to -1.49. The 95% confidence intervals for all these estimates do not contain the null. By contrast, we could not reject the null for non-Hispanic black mothers.

CONCLUSIONS: Whereas California findings generally support those from Scandinavia, the null results among non-Hispanic black mothers suggest that we do not detect adverse outcomes after a first-born male in all racial and/or ethnic groups.

Alternate JournalAnn Epidemiol
PubMed ID26265442
Grant ListUL1 TR001085 / TR / NCATS NIH HHS / United States