The exact frequency of breastmilk HIV transmission during the course of lactation remains unknown. Current international guidelines [UNAIDS 1998] state that the additional risk of mother to child transmission of HIV through breastfeeding (over and above that occurring in utero or during labour/delivery) is "about 15%". This figure comes from a meta-analysis [Dunn et al 1992] of 42 women with new infections and 1772 women with established infection. The majority of the women had breastfed for only 2 - 4 weeks and only l06 women breastfed longer than 6 months. The additional risk of transmission from breastmilk was estimated at 14% with established infection and 29% among newly infected women. The limits inherent in current testing techniques prevent identification of the HIV-infected infant at the time of birth. Since a baby who is not breastfed may test negative at birth and yet test positive any time in the next 90 days [Bagasra 1998] it remains speculative to say that breastfeeding provides the route of transmission in a breastfed baby who subsequently tests positive in the early postpartum [Black 1996].
The degree of exclusivity of breastfeeding in many case reports is unknown
and the definition of "breastfed" children, even in populations where breastfeeding
is routinely practised, almost certainly means babies who were, in fact,
only partially breastfed. The protective effects of breastfeeding against
ANY disease are known to be enhanced by increased exclusivity and longer
duration of breastfeeding and very
recent studies conducted in South Africa [Coutsoudis et al, 1999, 2000,
2001] confirm that there was no significant difference in HIV transmission
between babies who were exclusively breastfed for the first three months
of life and babies who were never breastfed, although babies who received
both breastmilk and formula were at significantly increased risk of transmission.
By 15 months, exclusive breastfeeders had the lowest transmission of all
three groups. Exclusive breastfeeding facilitates enterocyte junction closure
of the intestinal mucosal barrier, decreasing exposure to dietary antigens
and environmental pathogens which occur with the premature introduction
of other foods and liquids
(and formula), which in turn cause intestinal irritation and inflammation,
to allow direct contact of the virus with the infant's bloodstream [Smith
& Kuhn 2000, Morrison 1999].
Mortality at 2 years between babies of HIV-infected mothers randomized
to breast or formula feeding [Nduati et al, 2000] was 24% and 20% respectively,
a difference that was not considered to be statistically different, demonstrating
that there was no child survival advantage when breastfeeding was withheld.
Re-analysis of the infant mortality risks associated with not breastfeeding
in the first year of life in three developing countries, [WHO Collaborative
Study Team, 2000] found that the risk of death for infants under 2 months
from infectious disease was 6
times as likely if they were not breastfed; 4.1 times as likely from
2 - 3 months, and 2.6 times as likely from 4-5 months. The relevance of
these risk estimates for HIV+ mothers was identified. 2
Although one East African study has reported that the maternal mortality
rate of HIV-infected breastfeeding mothers exceeded that of the formula
feeding mothers in her study, [Nduati conference presentation 2000] closer
scrutiny shows that the computer randomization may somehow have put the
healthier women in the formula group since more women in the breastfeeding
arm had STDs, particularly syphilis, low levels of vitamin A, suffered
miscarriages, still-birth, c-sections, episiotomies, had greater than 4
hours rupture of membranes before birth and a higher percentage of
their babies were shown to be already infected at birth. No difference
in mortality rates between mothers who were breastfeeding, mixed feeding
or not breastfeeding at all were found in the South African study [Coutsoudis,
personal communication].
Summary
Although early research appears to show that breastfeeding increases
the risk of mother-to-child transmission of HIV, recent studies which clearly
define "breastfeeding" show no additional risk of MTCT of HIV through exclusive
breastfeeding over not breastfeeding at all. In addition, there is no difference
in the overall mortality rate at 2 years between children of HIV+ mothers
randomized to breast or bottle feeding. Since infant morbidity and mortality
are greatly enhanced whenever breastfeeding is abandoned, particularly
in resource-poor settings, it follows that public health measures which
seek to maximize child survival should continue to promote exclusive breastfeeding
for the first half year of life, and continued breastfeeding with the addition
of household weaning foods for up to two years or beyond, notwithstanding
maternal HIV status.
References:
Bagasra O, Is infection with HIV-1 possible during delivery and breastfeeding?
Guest Editorial AIDS Newsletter 1998 13(2): 1-2.
Black RF, Transmission of HIV-1 in the breast-feeding process. J Am Diet Assoc 1996;96:267-274.
Coutsoudis A, Pillay K, Spooner E, Kuhn L, Coovadia HM. Influence of infant feeding patterns on early mother-to-child transmission of HIV-1 in Durban, South Africa: a prospective cohort study. Lancet 1999;354:471-476.
Coutsoudis, A. Promotion of exclusive breastfeeding in the face of the HIV pandemic. Lancet 2000;356:1620-1621
Coutsoudis A, Pillay K, Kuhn L, Spooner E, Tsai W-Y, Coovadia HM for the South African Vitamin A Study Group. Method of feeding and transmission of HIV-1 from mothers to children by 15 months of age: prospective cohort study from Durban, South Africa. AIDS 2001;15:379-387.
Coutsoudis A, personal communication, March 2001
Dunn DT, Newell ML, Ades AE, Peckham CS, Risk of human immunodeficiency virus type 1 transmission through breastfeeding, Lancet 1992;340(8819)585-588. 3
Morrison P. HIV and infant feeding: to breastfeed or not to breastfeed: the dilemma of competing risks, Part 1. Breastfeeding Review 1999;7(2):5-13 Part 2. Breastfeeding Review 1999;7(3):11-19.
Nduati R, John G, Mbori-Ngacha D, Richardson B, Overbaugh J, Mwatha A, Ndinya-Achola J, Bwayo J, Onyango FE, Hughes J, Kreiss J. Effect of breastfeeding and formula feeding on transmission of HIV-1: a randomized clinical trial. JAMA 2000;283:1167-1174
Nduati R, Richardson B, John G, Mbori-Ngacha D,Overbaugh J, Mwatha T, Ndinya-Achola J, Bwayo J, Kreiss J. Impact of breastfeeding on maternal mortality among HIV-1 infected women: Results of a randomized clinical trial. WeOrC495, Durban Conference, 2000.
Smith MM & Kuhn L. Exclusive breastfeeding: does it have the potential to reduce breastfeeding transmission of HIV-1? Nutrition Reviews 2000;58:333-340.
UNAIDS/UNICEF/WHO 1998 HIV and Infant Feeding: A review of HIV transmission
through breastfeeding, WHO/FRH/NTU/CHD/98.3
WHO Collaborative Study Team. On the role of breastfeeding on the prevention
of infant mortality, effect of breastfeeding on infant and child mortality
due to infection diseases in less developed countries: a pooled analysis.
Lancet 2000; 355:451-55.
Prepared in March 2001 by:
PAMELA MORRISON, IBCLC
Harare
Zimbabwe
email: pamela@ecoweb.co.zw