A Twin Study of Breastfeeding With a Preliminary Genome-Wide Association Scan

• Published in: Twin research and human genetics 2015-02, Vol.18 (1), p.61-72
• Main Authors: Colodro-Conde, Lucia, Zhu, Gu, Power, Robert A., Henders, Anjali, Heath, Andrew C., Madden, Pamela A. F., Montgomery, Grant W., Medland, Sarah, Ordoñana, Juan R., Martin, Nicholas G.
• Format: Article
• Language: English
• Subjects: 19th century; Adult; Aged; Aged, 80 and over; Australia; Births; Body mass index; Breast; Breast feeding; Breast Feeding - statistics & numerical data; Breast Feeding - trends; Breastfeeding & lactation; Breasts; Children & youth; Chromosomes, Human - genetics; Cohort Studies; Data collection; Environmental factors; Female; Genetic diversity; Genome-wide association studies; Genome-Wide Association Study; Genomes; Genotyping Techniques; Humans; Male; Medical personnel; Middle Aged; Mothers; Oligonucleotide Array Sequence Analysis; Overweight; Polygenic inheritance; Polymorphism, Single Nucleotide; Quality control; Questionnaires; Reproductive History; Retrospective Studies; Self Report; Surveys and Questionnaires; Twin studies; Twins; Twins, Dizygotic - genetics; Twins, Dizygotic - psychology; Twins, Dizygotic - statistics & numerical data; Twins, Monozygotic - genetics; Twins, Monozygotic - psychology; Twins, Monozygotic - statistics & numerical data; Womens health
• ISSN: 1832-4274; 1839-2628
• DOI: 10.1017/thg.2014.74

Breastfeeding has been an important survival trait during human history, though it has long been recognized that individuals differ in their exact breastfeeding behavior. Here our aims were, first, to explore to what extent genetic and environmental influences contributed to the individual differences in breastfeeding behavior; second, to detect possible genetic variants related to breastfeeding; and lastly, to test if the genetic variants associated with breastfeeding have been previously found to be related with breast size. Data were collected from a large community-based cohort of Australian twins, with 3,364 women participating in the twin modelling analyses and 1,521 of them included in the genome-wide association study (GWAS). Monozygotic (MZ) twin correlations (r MZ = 0.52, 95% CI 0.46–0.57) were larger than dizygotic (DZ) twin correlations (r DZ = 0.35, 95% CI 0.25–0.43) and the best-fitting model was the one composed by additive genetics and unique environmental factors, explaining 53% and 47% of the variance in breastfeeding behavior, respectively. No breastfeeding-related genetic variants reached genome-wide significance. The polygenic risk score analyses showed no significant results, suggesting breast size does not influence breastfeeding. This study confers a replication of a previous one exploring the sources of variance of breastfeeding and, to our knowledge, is the first one to conduct a GWAS on breastfeeding and look at the overlap with variants for breast size.