The World Health Organization (WHO), the American College of Obstetricians and Gynecologists (ACOG), and the American Academy of Pediatrics (AAP) recommend breastfeeding within the first hour of life and that infants be exclusively breastfed for the first six months of life with the exception of those with specific medical conditions that preclude breastfeeding.1-5 They further recommend that children continue to be breastfed for two years or beyond with supplementary solid, semi-solid, or soft foods being introduced at six months of age.
Breastmilk is a uniquely safe and healthy sustenance option for newborns. Breastmilk has been shown to meet all the nutritional needs of infants up to six months of age.1,2,4 The WHO and AAP warn against mixed feeding of infants before six months of age, including supplementing with formula. Evidence has shown that exclusive breastfeeding for the first six months of life provides numerous benefits that are lessened with the introduction of other foods or liquids in addition to breast milk.
Benefits to infants include breastmilk being a safe, clean, healthy, and accessible source of nutrition, boosting immune support, improving cognitive development, reducing the risk of developing childhood cancers, and aiding with bonding. Increasing evidence also points to breastfeeding being beneficial to the mother, including reducing the risk of breast and ovarian cancer.
Immune Support
Breastmilk contains antibodies that can help improve infants’ immune health, including protecting against various forms of infection. A 2010 case-control study (n=399) was conducted including infants between the ages of 3 days to 6 months with a birth weight >1,500 g and born after 32 weeks’ gestation.6 Cases had a hospital admission of at least 24 hours, and causes included neonatal sepsis, pneumonia, diarrhea, and other infections. Rates of exclusive breastfeeding and mixed breastfeeding were similar between cases and controls. However, rates of exclusive formula feeding were significantly higher among cases (33.0% vs 14.9%, adjusted Odds Ratio [OR] 3.7, p<0.001).
Exclusivity and duration of breastfeeding have been associated with contracting fewer common infections during early childhood, including ear, throat, and sinus infections. A 2014 prospective study (n=1,542) used data from the Infant Feeding Practices Study II, a longitudinal study conducted by the US Food and Drug Administration and the Centers for Disease Control and Prevention from 2005-2007, as well as follow-up data collected when the children were 6 years old.7 The prevalence of infections in the past year was lower among six-year-olds who breastfed compared to those who never breastfed (24.6% vs 28.0% for ear infection, 22.8% vs 29.7% for throat, and 14.6% vs 22.3% for sinus). Prevalence decreased with increased duration of any breastfeeding ranging from >0 to <3 months, 3 to <6 months, 6 to <9 months, and ≥9 months (28.1, 28.0, 24.6, and 21.4% for ear infection; 26.1, 25.2, 23.1, and 20.1% for throat infection; 20.9, 15.4, 13.4, and 10.8% for sinus infection). Similarly, prevalence decreased with increased duration of exclusive breastfeeding ranging from >0 to <4 months, 4 to <6 months, and ≥6 months (26.4, 19.5, and 11.6% for ear infection; 24.2, 20.0, and 7.0% for throat infection; 15.9, 11.3, and 2.3% for sinus infection). Those who were breastfed for ≥6 months with formula introduced after six months of age had a lower prevalence of infection (20.5% for ear, 18.6% for throat, 10.4% for sinus) compared to those who breastfed for <6 months (28.1% for ear, 25.8% for throat, 19.1% for sinus) and those breastfed for ≥6 months with supplemental formula used before six months of age (24.6% for ear, 23.5% for throat, 13.0% for sinus).
Breastfeeding has also been shown to reduce the incidence of necrotizing enterocolitis (NEC), a leading cause of death in preterm infants, with an estimated 13.4% mortality rate among infants weighing 500-1,000 g.8 A 2016 secondary analysis of the National Institute of Child Health and Human Development Glutamine Trial dataset explored the relationship between exclusive breastfeeding and NEC burden.8 Among the 848 infants included, the incidence of NEC was considerably higher among those who were exclusively fed formula (11.1%) compared to those on a mixed diet (<98% of a diet comprised of breastmilk; 8.2% NEC incidence) or predominantly breastmilk diet (≥98% of a diet comprised of breastmilk; 1.3% NEC incidence).
Overweight and Obesity
Evidence has shown that breastfeeding is associated with a reduced risk of being overweight or obese in childhood. A 2015 analysis of the data from the German Health Interview and Examination Survey for Children and Adolescents (KiGGS) conducted between 2003-2006 (n=8,034) found that those who breastfed for ≥4 months had significantly reduced odds of being overweight or obese during childhood compared those who were breastfed for <4 months (11.6% vs 17.4% for overweight, Odds Ratio [OR] 0.81, p<0.001; 4.2% vs 7.4% for obesity, OR 0.75, p<0.001).9
Cognitive Development
Breastfeeding may help with a baby’s brain development, but whether this is due to breastfeeding or increased physical intimacy, touch, and/or eye contact is unknown. A 2008 randomized trial (n=13,889) explored the effects of breastfeeding on cognitive ability.10 A cohort of children with similar baseline sociodemographic and clinical variables were followed from birth to six and half years of age, at which time their intelligence quotient (IQ) was assessed using the Wechsler Abbreviated Scales of Intelligence (WASI; full-scale IQ score ranges from 40-160). Children who had been exclusively breastfed for 3-6 months and ≥6 months had a moderately higher IQ compared to those who had been breastfed for <3 months (3.3 points higher for 3-6 months and 5.6 points higher for ≥6 months). The results suggest prolonged and exclusive breastfeeding may improve children's cognitive development.
A 2016 study investigated the association between breastfeeding and cognitive development in infants during their first three years. 11 The study was a part of the Mothers’ and Children’s Environmental Health (MOCEH) study, which was a multi-center birth cohort project in Korea that began in 2006. 697 infants were tested at ages 12, 24, and 36 months using the Korean version of the Bayley Scales of Infant Development II (K-BSID-II) to determine their mental development index (MDI) score. The results indicated a positive correlation between breastfeeding duration and MDI score. Compared to infants who were not breastfed, breastfeeding for ≥12 months had a 6.9-point difference in MDI score at 1 year old, a 6.5-point difference at 2 years old, and an 8.3-point difference at 3 years old. These results suggest that a longer duration of breastfeeding improves cognitive development in infants.
Childhood Cancers
In a case-control study published in 2010, researchers investigated the link between acute leukemia and factors related to early immune system stimulation.12 A total of 634 acute lymphoblastic leukemia (ALL) cases and 86 acute myeloblastic leukemia (AML) cases were compared to 1,494 controls. The findings suggest a negative correlation between breastfeeding duration and the risk of ALL, especially notable for breastfeeding durations of ≥6 months and ≥12 months. Children breastfed for <6 months have approximately 4.34 times higher risk of developing ALL compared to those breastfed for at least 6 months (34.3% vs 7.9%, Odds Ratio [OR] 0.7, 95% CI [0.5-1.0), indicating the potential protective effect of longer breastfeeding against ALL in children.
Mortality
Breastfeeding is associated with lower overall infant mortality rates. A 2006 cluster-randomized double-blind control trial of 10,947 breastfed infants at least two days old found that exclusively breastfeeding and predominantly breastfeeding (defined as feeding breastmilk and other nonmilk fluids) to significantly lower risk of neonatal mortality compared to partial breastfeeding (defined as feeding breastmilk and animal milk, formula, or solids).13 The incidence of mortality in the first 28 days of life among those who exclusively breastfed was 1.1% compared to 1.6% for predominantly breastfed and 5.6% for partially breastfed.
A 2005 secondary analysis of data from a multicenter randomized control trial (n=9,424) had similar findings.14 There was no significant difference in all-cause mortality between infants who were exclusively and predominantly breastfed, but rates were significantly higher for those who were partially or not breastfed. Mortality rates in the first 26 weeks of life were 2.2 deaths per 100 person-years for exclusive breastfeeding, 2.4 for predominant breastfeeding, 4.1 for partial breastfeeding (adjusted Hazard Ratio [HR] 2.46, p=0.001), and 19.5 for no breastfeeding (adjusted HR 10.5, p<0.001). Notably, the sample size was limited for infants that were not breastfed (61.5 person-years compared to 3,202.0 for all other diet modalities combined).
Bonding and Emotional Benefits
Breastfeeding promotes feelings of closeness and bonding between the parent and baby, which can enhance maternal well-being, promote feelings of security, and reduce the risk of postpartum depression.
A 2017 randomized-control trial (n=71) found that implementing bonding education including encouraging breastfeeding can increase mother-infant attachment.15 The intervention group received three sessions of supportive group education sessions around bonding with their baby and the role of breastfeeding. The Muller Maternal Attachment Inventory (MMAI, scored 26-104 with higher scores suggesting stronger attachment) was utilized to assess the level of attachment. In the intervention group, all mothers breastfed for at least one year compared to 86% of controls. MMAI scores were 16.22 points higher among the intervention group compared to controls (90.74 vs 74.52, p=0.001) within 3-7 days of childbirth. The intervention group continued to have 10.35-point higher scores through 12 months after childbirth (97.71 vs 87.36, p<0.001). Additionally, each one-point increase in MMAI scores was associated with a one-point decrease in depression scores as assessed using the General Health Questionnaire (GHQ, subtests scored 0-21 with scores ≥6 indicating the presence of psychiatric symptoms).
A longitudinal study published in 2003 (n=570) examined the impact of breastfeeding vs bottle-feeding on the maternal bond and mother-infant relationship during the pregnancy and at 4 and 12 months postpartum.16 Using the Parent-Child Early Relational Assessment Scale (PCERA), which scores from 1 to 5 (higher scores indicating greater positive correlation), breastfeeding dyads scored higher. At 12 months, breastfeeding infants showed less dysregulation and irritability (3.07 vs 2.83, p<0.5) and better mutual interaction and reciprocity during play (3.25 vs 3.02, p<0.5) compared to bottle-fed infants. These findings suggest that breastfeeding may promote more positive outcomes in infant behavior regulation and dyadic interaction at 12 months compared to bottle feeding.
Post-Partum Depression
A 2012 prospective study (n=137) found that breastfeeding was associated with lower rates of postpartum depression as assessed by the Mini International Neuro-psychiatric Interview (MINI) and Edinburgh Postnatal Depression Scale (EPDS; scored 0-30 with scores over 10 indicating possible depression).17 Four months postpartum, 26.3% of those who didn’t breastfeed had depression compared to 3.3% of those who did breastfeed (p=0.0025). Those who didn’t breastfeed had higher EPDS scores, with a mean score of 8.1 vs 4.5 for those who did breastfeed.
Breast and Ovarian Cancer
A 2020 matched case-control study found that breastfeeding is linked to a reduced risk of ovarian cancer. 18 The study involved 1,650 cases and 2,702 controls who completed questionnaires on family history, breastfeeding, pregnancy history, and contraceptive use. Breastfeeding was more common among controls than those with ovarian cancer (64.9% control vs 58.9% cases, OR 0.77, 95% Confidence Interval [CI] [0.66-0.90], p=0.001). Those with ovarian cancer reported shorter cumulative breastfeeding duration than controls (13.0 vs 14.5 months). The incidence of ovarian cancer was lower among those who breastfed for ≥7 months compared to those who never breastfed (33.0% vs 41.7%). Risk reduction associated with having breastfed and duration of breastfeeding was consistent across BRCA gene status and age at diagnosis. These findings suggest a protective effect of breastfeeding for at least seven months among women even if they have a BRCA1 or BRCA2 mutation.
Another study published in 2020 found a significant reduction in the risk of ovarian cancer associated with breastfeeding.19 The study analyzed 9,973 women with ovarian cancer and 13,843 controls from 13 case-control studies. Breastfeeding was associated with a significantly lower risk of invasive ovarian cancer, with a decreasing risk for a longer duration of breastfeeding. Among those with ovarian cancer, 5% reported having breastfed ≥12 months (7% control, OR 0.66), 5% breastfed 9-<12 months (7% control, OR 0.66), 9% 6-<9 months (11% control, OR 0.69), 17% 3-<6 months (19% control, OR 0.75), 24% 0-<3 months (25% control, OR 0.82), and 41% reporting never having breastfed (32% control, reference). The authors noted that the biological mechanisms through which breastfeeding could reduce ovarian cancer risk were not well understood. However, these findings suggest that breastfeeding has the potential to help lower the risk of ovarian cancer.
Similar findings have been published for breastfeeding and breast cancer. A 2002 meta-analysis of 42 case-control and 5 cohort studies found that fewer women with breast cancer (n=50,302) had ever breastfed than women without breast cancer (n=96,973) (71% vs 79%). 20 The average duration of breastfeeding was shorter among those with breast cancer as well (9.8 vs 15.6 months). Among those with breast cancer, 15.3% reported having breastfed ≥19 months (24.8% control, Relative Risk [RR] 0.89), 24.9% breastfed 7-18 months (26.2% control, RR 0.94), 30.3% ≤6 months (28.0% control, RR 0.98), and 29.4% reporting never having breastfed (21.0% control, reference).
References
- Indicators for assessing infant and young child feeding practices: definitions and measurement methods. Geneva: World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF); 2021.
- Global Strategy for Infant and Young Child Feeding. World Health Organization (WHO) and the United Nationas Children's Fund (UNICEF); 2003.
- Committee Opinion No. 658 Summary: Optimizing Support For Breastfeeding As Part Of Obstetric Practice. Obstet Gynecol. Feb 2016;127(2):420-1. doi:10.1097/aog.0000000000001311
- Meek JY, Noble L. Policy Statement: Breastfeeding and the Use of Human Milk. Pediatrics. Jul 1 2022;150(1)doi:10.1542/peds.2022-057988
- Johnston M, Landers S, Noble L, Szucs K, Viehmann L. Breastfeeding and the use of human milk. Pediatrics. Mar 2012;129(3):e827-41. doi:10.1542/peds.2011-3552
- Hengstermann S, Mantaring JB, 3rd, Sobel HL, et al. Formula feeding is associated with increased hospital admissions due to infections among infants younger than 6 months in Manila, Philippines. J Hum Lact. Feb 2010;26(1):19-25. doi:10.1177/0890334409344078
- Li R, Dee D, Li CM, Hoffman HJ, Grummer-Strawn LM. Breastfeeding and risk of infections at 6 years. Pediatrics. Sep 2014;134 Suppl 1(Suppl 1):S13-20. doi:10.1542/peds.2014-0646D
- Colaizy TT, Bartick MC, Jegier BJ, et al. Impact of Optimized Breastfeeding on the Costs of Necrotizing Enterocolitis in Extremely Low Birthweight Infants. J Pediatr. Aug 2016;175:100-105.e2. doi:10.1016/j.jpeds.2016.03.040
- Grube MM, von der Lippe E, Schlaud M, Brettschneider AK. Does breastfeeding help to reduce the risk of childhood overweight and obesity? A propensity score analysis of data from the KiGGS study. PLoS One. 2015;10(3):e0122534. doi:10.1371/journal.pone.0122534
- Kramer MS, Aboud F, Mironova E, et al. Breastfeeding and child cognitive development: new evidence from a large randomized trial. Arch Gen Psychiatry. May 2008;65(5):578-84. doi:10.1001/archpsyc.65.5.578
- Lee H, Park H, Ha E, et al. Effect of Breastfeeding Duration on Cognitive Development in Infants: 3-Year Follow-up Study. J Korean Med Sci. Apr 2016;31(4):579-84. doi:10.3346/jkms.2016.31.4.579
- Rudant J, Orsi L, Menegaux F, et al. Childhood acute leukemia, early common infections, and allergy: The ESCALE Study. Am J Epidemiol. Nov 01 2010;172(9):1015-27. doi:10.1093/aje/kwq233
- Edmond KM, Zandoh C, Quigley MA, Amenga-Etego S, Owusu-Agyei S, Kirkwood BR. Delayed breastfeeding initiation increases risk of neonatal mortality. Pediatrics. Mar 2006;117(3):e380-6. doi:10.1542/peds.2005-1496
- Bahl R, Frost C, Kirkwood BR, et al. Infant feeding patterns and risks of death and hospitalization in the first half of infancy: multicentre cohort study. Bull World Health Organ. Jun 2005;83(6):418-26.
- Shariat M, Abedinia N. The Effect of Psychological Intervention on Mother-Infant Bonding and Breastfeeding. 2017;doi:10.22038/ijn.2017.16673.1191
- Else-Quest NM, Shibley J, Clark H, Clark R. Breastfeeding, Bonding, and the Mother-Infant Relationship. Merrill-Palmer Quarterly. October 2003 2003;49(4):495-517.
- Hamdan A, Tamim H. The relationship between postpartum depression and breastfeeding. Int J Psychiatry Med. 2012;43(3):243-59. doi:10.2190/PM.43.3.d
- Kotsopoulos J, Gronwald J, McCuaig JM, et al. Breastfeeding and the risk of epithelial ovarian cancer among women with a BRCA1 or BRCA2 mutation. Gynecol Oncol. Dec 2020;159(3):820-826. doi:10.1016/j.ygyno.2020.09.037
- Babic A, Sasamoto N, Rosner BA, et al. Association Between Breastfeeding and Ovarian Cancer Risk. JAMA Oncol. Jun 01 2020;6(6):e200421. doi:10.1001/jamaoncol.2020.0421
- Breast cancer and breastfeeding: collaborative reanalysis of individual data from 47 epidemiological studies in 30 countries, including 50302 women with breast cancer and 96973 women without the disease. Lancet (London, England). Jul 20 2002;360(9328):187-95. doi:10.1016/s0140-6736(02)09454-0
