Objective: To examine whether induction of labor and epidural analgesia are associated with breastfeeding initiation, maintenance, and breastfeeding problems. Design: Population-based longitudinal cohort study. Setting: The Norwegian Mother, Father and Child Cohort Study (MoBa), linked with data from the Medical Birth Registry of Norway. Sample: A total of 73,069 mothers with singleton infants and vaginal births. Methods: Information on induction of labor, method of induction, and epidural analgesia were obtained from registry data. Breastfeeding initiation, maintenance of breastfeeding at six months, and breastfeeding problems were reported by mothers six months postpartum. Logistic regression analyses estimated associations between birth interventions and breastfeeding outcomes, adjusting for several maternal sociodemographic and obstetric variables, and maternal and fetal health. Main outcome measures: Initiation of breastfeeding within the first week, maintenance of breastfeeding to six months postpartum, and reported breastfeeding problems. Results: Induction of labor was associated with reduced likelihood of initiating breastfeeding (adjusted OR 0.65, 95% CI 0.56 - 0.77) and maintaining breastfeeding at six months (adjusted OR 0.86, 95% CI 0.81 – 0.91), and with increased likelihood of breastfeeding problems (adjusted OR 1.11, 95% CI 1.01 – 1.22). Epidural analgesia was also associated with lower initiation (adjusted OR 0.68, 95% CI 0.59 – 0.77) and maintenance (adjusted OR 0.79, 95% CI 0.76 – 0.83), and higher rates of breastfeeding problems (adjusted OR 1.12, 95% CI 1.05 – 1.21). Conclusion: Induction of labor and epidural analgesia may be a risk factor for reduced likelihood of breastfeeding. Awareness can help clinicians target individualized breastfeeding support postpartum.

Objective: To examine the effect of prenatal maternal anxiety on birthweight and preterm birth, controlling for genetic confounding using a sibling comparison design. Design: This is a population-based prospective cohort study with a comparison of a population level analysis and a sibling analysis. Setting: This study is based on the Norwegian Mother, Father and Child Cohort Study (MoBa) conducted by the Norwegian Institute of Public Health (https://www.fhi.no/en/studies/moba/ ). Sample: Women and their chiold participating in the MoBa (n= 78,117) and women participating with more than one pregnancy (n=12,480). Methods: Associations between prenatal maternal anxiety (measured across the 17th and 30th weeks) and birth outcomes (birthweight and gestational age) were examined using linear regression with adjustment for family-shared confounding in a sibling comparison design. Main outcomes: Birthweight (in grams) and gestational age (ultrasound measure in days) were obtained from the Medical Birth Registry of Norway. Results: The maternal anxiety score during pregnancy was inversely associated with newborn’s birthweight (Beta = -112,8 95% CI: –142.7, -83.0) and gestational age (Beta=-1.77, 95% CI: -2.42, -1.13) after adjustment for several covariates. The association of the maternal anxiety score with both newborn’s birthweight (Beta=-173.9, 95% CI: -252.3, -95.4) and gestational age (Beta=-1.08, 95% CI: -2.91, -0.75) remained but was largely weakened after further adjusting for the shared-family confounding in the sibling comparison design. Conclusion: The link between maternal prenatal anxiety and birthweight and gestational age remained after adjusting for shared family confounding, yet estimates were weakened after adjusting for environmental covariates.