Infant Feeding Practices were not Associated with Breast Milk HIV-1 RNA Levels in a Randomized Clinical Trial in Botswana

Exclusive breastfeeding has been associated with a reduced risk of late vertical HIV transmission as compared to an infant diet composed of breast milk mixed with supplemental foods or liquids. Hypothesized mechanisms include increased infectivity of breast milk from mothers who practice mixed breastfeeding (MBF), or mechanisms such as increased gastrointestinal permeability in the infant caused by mixed feeding. It has been proposed that MBF may result in subclinical mastitis and higher breast milk HIV titers. However, little is known about the relationship between feeding strategy and breast milk viral load. We measured the HIV-1 concentration in breast milk in a sub-cohort of women enrolled in a mother-to-child HIV transmission prevention trial (the "Mashi" study). We report no observed relationship between MBF and measured breast milk viral RNA load. Our findings suggest that the increased transmission risk associated with higher breast milk HIV-1 RNA during MBF is unlikely.     

Factors influencing breast milk HIV RNA viral load among Zambian women

In a longitudinal cohort study we investigated factors contributing to breast milk HIV RNA viral load among lactating women in Lusaka, Zambia. Detailed data from 135 HIV-infected women were collected by questionnaires concerning postpartum maternal and infant health and infant feeding practice. Maternal blood was collected during pregnancy and at 6 weeks postpartum. Milk samples collected from each breast at 10 days and 6 weeks postpartum plus a subset collected at other time points were analyzed for HIV RNA viral load. Increased milk viral load was associated in univariate analyses with maternal symptoms of poor health, raised plasma alpha(1)-acid glycoprotein (AGP) at week 6, raised milk sodium/potassium (Na/K) ratio, postpartum need for antibiotics, preterm delivery, and low birth weight infants. In a multiple regression 49% of variability in mean milk viral load was explained by milk Na/K ratio and need for antibiotics, with borderline contributions from plasma AGP and plasma viral load. Maternal blood hemoglobin or receipt of iron supplements and infant feeding variables such as changing the infant's diet by moving from exclusive to nonexclusive breastfeeding or adding solid foods were not associated with milk viral load. Thus maternal health was the main factor contributing to milk viral load. The lack of effect of feeding practices on milk viral load and the previously determined association of poor maternal health with reduced duration of exclusive breastfeeding in this cohort suggest the relation between exclusive breastfeeding and decreased HIV transmission may be secondary to poor maternal health.     

Post-weaning breast milk HIV-1 viral load, blood prolactin levels and breast milk volume

BACKGROUND: The effect of abrupt weaning, advocated as a safe transition from exclusive breastfeeding in HIV-exposed children, on the quantity of HIV viral load in breast milk (BMVL) is not known. OBJECTIVES: To determine the effect of abrupt cessation of breastfeeding on serum prolactin, pumped breast milk volume and BMVL obtained 2 weeks after rapid weaning in HIV-infected women. METHODS: Women enrolled in a prospective study (ZEBS) were randomized to abruptly wean at 20 weeks postpartum or continue exclusive breastfeeding. Breast milk was obtained at 22 weeks by electric breast pump over 10 min from 222 women who had either weaned or continued to breastfeed. Pre- and post-pumping prolactin was measured. BMVL was measured at 20 and 22 weeks in 71 randomly selected women from both groups. RESULTS: Baseline prolactin and breast milk volume was significantly lower among women who had weaned. Detectable (68 versus 42%; P = 0.03) and median BMVL (448 versus < 50 copies/ml; P = 0.005) was significantly higher among those who had weaned in comparison with those who were still breastfeeding and was significantly higher in the same women after weaning compared with 2 weeks earlier (P = 0.001). CONCLUSIONS: BMVL is substantially higher after rapid weaning and this may pose an increased risk of HIV transmission if children resume breastfeeding after a period of cessation. Increases in BMVL with differing degrees of mixed feeding needs to be assessed.     

Breastmilk RNA viral load in HIV-infected South African women: effects of subclinical mastitis and infant feeding

OBJECTIVE: To investigate determinants of breastmilk RNA viral load among HIV-infected South African women, with particular attention to infant feeding mode and subclinical mastitis. DESIGN: Observational, longitudinal study. METHODS: Information on current infant feeding practice and a spot milk sample from each breast were obtained from 145 HIV-infected lactating women at 1, 6 and 14 weeks postpartum. The sodium/potassium (Na+/K+) ratio in milk was taken as an indicator of subclinical mastitis. The association between milk RNA viral load and maternal and infant characteristics was investigated using uni- and multivariate models. RESULTS: Milk viral load was below the limit of detection of the HIV RNA assay (< 200 copies/ml) in 63/185 (34.1%), 73/193 (37.8%) and 68/160 (42.5%) of samples at 1, 6 and 14 weeks, respectively. Multivariate models predicted between 13 and 26% of variability in milk viral load in the first 14 weeks. Low blood CD4 cell count (< 200 x 10(6) cells/l) during pregnancy and raised milk Na+/K+ ratio were significantly associated with raised milk RNA viral load at all times, but there were no consistent associations between infant feeding mode and RNA viral load in milk. There was a non-significant trend for the six infants known to be infected postnatally, compared with the 88 infants who remained uninfected, to have been exposed to breastmilk of higher viral load at each time point. CONCLUSIONS: Breast milk HIV RNA viral load in the first 14 weeks of life varied; high levels were associated with subclinical mastitis and severe maternal immunosuppression. Multivariate models had limited predictive value for milk RNA viral load, illustrating the multiple contributors to viral load.     

Human immunodeficiency virus load in breast milk, mastitis, and mother-to-child transmission of human immunodeficiency virus type 1.

Human immunodeficiency virus (HIV) type 1 load in breast milk and mastitis were examined as risk factors for vertical transmission of HIV-1. Six weeks after delivery, HIV-1 load and sodium (an indicator of mastitis) were measured in breast milk from 334 HIV-1-infected women in Malawi. Median breast milk HIV-1 load was 700 copies/mL among women with HIV-1-infected infants versus undetectable (<200 copies/mL) among those with uninfected infants, respectively (P<. 0001). Elevated breast milk sodium levels consistent with mastitis occurred in 16.4% of HIV-1-infected women and were associated with increased vertical transmission of HIV-1 (P<.0001). Median breast milk HIV-1 load was 920 copies/mL among women with versus undetectable among those without elevated breast milk sodium levels, respectively (P<.0001). Mastitis and breast milk HIV-1 load may increase the risk of vertical transmission of HIV-1 through breast-feeding.     

Breast milk alpha-defensins are associated with HIV type 1 RNA and CC chemokines in breast milk but not vertical HIV type 1 transmission

Alpha-defensins are proteins exhibiting in vitro anti-HIV-1 activity that may protect against mother-to-child transmission of HIV-1 via breast milk. Correlates of alpha-defensins in breast milk and transmission risk were determined in a cohort of HIV-1-infected pregnant women in Nairobi followed for 12 months postpartum with their infants. Maternal blood was collected antenatally and at delivery for HIV-1 viral load and infant HIV-1 infection status was determined < 48 h after birth and at months 1, 3, 6, 9, and 12. Breast milk specimens collected at month 1 were assayed for alpha-defensins, HIV-1 RNA, subclinical mastitis, and CC and CXC chemokines. We detected alpha-defensins in breast milk specimens from 108 (42%) of 260 HIV-1-infected women. Women with detectable alpha-defensins (> or =50 pg/ml) had a median concentration of 320 pg/ml and significantly higher mean breast milk HIV-1 RNA levels than women with undetectable alpha-defensins (2.9 log(10) copies/ml versus 2.5 log(10) copies/ml, p = 0.003). Increased alpha-defensins concentrations in breast milk were also associated with subclinical mastitis (Na (+)/K(+) ratio > 1) and increased breast milk chemokine levels. Overall, 40 (15%) infants were HIV-1 uninfected at birth and subsequently acquired HIV-1. There was no significant association between month 1 alpha-defensins and risk of HIV-1 transmission. In conclusion, alpha-defensins were associated with breast milk HIV-1 viral load, chemokine levels, and subclinical mastitis, all of which may alter risk of infant HIV-1 acquisition. Despite these associations there was no significant relationship between breast milk alpha-defensins and mother-to-child transmission, suggesting a complex interplay between breast milk HIV-1, inflammation, and antiinfective factors.     

Maternal plasma viral load, zidovudine and mother-to-child transmission of HIV-1 in Africa: DITRAME ANRS 049a trial

OBJECTIVE: To study the relationship between maternal plasma RNA levels and mother-to-child transmission (MTCT) of HIV-1 in African breastfed children. DESIGN: Nested case-control study within a randomized trial assessing the efficacy of a short maternal zidovudine (ZDV) regimen to reduce MTCT. METHODS: Eligible women received either 300 mg of ZDV twice a day until labour, 600 mg at the beginning of labour and 300 mg twice a day for 7 days post-partum or a placebo. The diagnosis of paediatric HIV-1 infection was based on PCR tests at days 1--8, 45, 90 and 180 then on serology performed at 3 monthl intervals. Plasma HIV-1 RNA was measured at inclusion and on day 8 after delivery for all women who did transmit HIV to their children (cases) using a Chiron branched DNA assay (sensitivity 50 copies/ml) and compared with women who did not transmit (two per case) matched for phase trial, treatment allocation and site. RESULTS: At inclusion, mean log10 viral load was 4.6 among 55 transmitting mothers and 3.7 among 117 non transmitters (P = 0.0001). Among transmitters, the mean difference in log10 viral load between day 8 post-partum and inclusion was -0.13 in the ZDV group (n = 23) versus 0.27 in the placebo group (n = 32; P = 0.01); among non transmitters it was -0.35 for the ZDV group (n = 47) versus 0.27 in the placebo group (n = 70; P < 10(-4)). In multivariate logistic regression analysis, odds ratios for MTCT were 8.7 (95% confidence interval, 3.7-20.6) for 1 log(10) increase of maternal RNA at inclusion and 4.2 (95% confidence interval, 1.7--10.3) for 1 log(10) increase difference from inclusion to day 8 post-partum. CONCLUSION: High maternal viral load at inclusion strongly predicts MTCT of HIV in Africa. A short ZDV treatment regimen decreases significantly maternal viral load from its pretreatment level.     

Subtype C Is associated with increased vaginal shedding of HIV-1

The prevalence of human immunodeficiency virus (HIV)-1-infected cells and HIV-1 RNA levels in genital secretions and breast milk and the risk of mother-to-child transmission of HIV-1 were compared among subtypes A, C, and D in a Kenyan cohort. Pregnant women infected with subtype C were significantly more likely to shed HIV-1-infected vaginal cells than were those infected with subtype A or D (odds ratio [OR], 3.6 [95% confidence interval {CI}, 1.4-8.8]; P = .006). This relationship held after adjusting for age, CD4 cell count, and plasma HIV-1 RNA load (OR, 3.1 [95% CI, 1.1-8.6]; P = .03). These observations suggest that HIV-1 subtype influences mucosal shedding of HIV-1.     

Predictors of intrauterine and intrapartum transmission of HIV-1 among Tanzanian women.

OBJECTIVE: To examine predictors of vertical transmission of HIV-1 in Dar-es-Salaam, Tanzania. DESIGN: Observational design. METHODS: Consenting HIV-1-infected pregnant women (n = 1078) were enrolled in a trial to examine the role of vitamin supplements. Intrauterine HIV-1 infection (HIV-positive at birth); intrapartum and early breastfeeding transmission (HIV-positive at 6 weeks among those uninfected at birth) were defined using the PCR. RESULTS: Of 734 infants who had a specimen taken at birth, 62 were HIV positive [8.4%; 95% confidence interval (CI),6.4--10.5%], whereas 59 infants were positive among 367 infants who were uninfected at birth and were retested at 6 weeks (16.1%; 95%CI, 12.3--19.8%). In multivariate analyses, maternal CD4 cell count, viral load, and clinical stage were significant predictors of both definitions of transmission. Viral load of 50 000 copies/ml or more at delivery was associated with a 4.21-fold increase in risk of intrapartum and early breastfeeding transmission (95%CI, 1.59--11.13;P = 0.004). Babies who were HIV negative at birth and born before 34 weeks of gestation were 2.19 times more likely to become infected during intrapartum and early breastfeeding periods compared with those born after 37 weeks (95%CI, 1.19--4.04; P = 0.01). Gonorrhea at baseline was related to intrauterine transmission [multivariate risk ratio (RR), 5.50; 95%CI, 2.04--14.81; P < 0.001] but not intrapartum and early breastfeeding transmission. Signs of lower genital infections at or after enrollment were also associated with transmission. CONCLUSIONS: Reducing prematurity, rate of HIV disease progression, and maternal viral load at or after delivery could help to reduce vertical transmission. Treatment of sexually transmitted infections at onset of prenatal care, about 20 weeks on average, was inadequate for prevention of transmission. Whether sustained clearance of lower genital tract infections result in reduced transmission remains to be determined.     

Reduced fertility among HIV-infected women associated with viral load in Rakai district, Uganda

We assessed whether HIV-1 viral load affects the likelihood of live birth among HIV-positive women in a nested case-control study of HIV-positive women from a community cohort in Rakai District, Uganda. Cases were women who had a live birth (n = 270), and controls were sexually active women who did not use contraception and did not become pregnant during follow-up (n = 263). In women with a live birth and non-pregnant controls, median HIV viral loads were 4.12 log(10) copies/mL and 4.41 log(10) copies/mL, respectively (P = 0.001). A non-linear association was observed, and a segmented linear regression with spline knot at 4.5 log(10) copies/mL was fit. We observed a decline in the log (adjusted odds ratio [adj. OR])= -0.08 (95% confidence interval [CI]: -0.36, 0.20) between 3.0 and 4.49 log(10) viral load and -0.92 (95% CI: -1.21, -0.63) between 4.5 and 6.5 log(10) viral load. The two reductions differed significantly from one another (P < 0.001). Each increase in log(10) viral load after 4.5 log(10) resulted in an adj. OR of live birth which was 12% of the previous viral load category. Our data suggest that there may be considerable differences in the ability to produce a live birth among HIV-positive women with high viral loads.     

Women living with HIV in high‐income settings and breastfeeding

Guidelines in high‐income settings recommend breastfeeding avoidance amongst women living with HIV (WLWH). Increasingly, WLWH in high‐income settings, who are well‐treated with fully suppressed viral loads, are choosing to breastfeed their infants, even with these recommendations. The purpose of this article is to review existing research and guidance on infant feeding amongst WLWH in high‐income countries and to identify gaps in this evidence that require further investigation. Current evidence on the risk of HIV transmission through breastfeeding in the context of antiretroviral therapy (ART), the significance of cell‐associated virus, transmission risk factors, retention in care and adherence postpartum, infant prophylaxis and antiretroviral exposure, and monitoring of the breastfeeding WLWH are summarized. A latent HIV reservoir is persistently present in breast milk, even in the context of ART. Thus, suppressive maternal ART significantly reduces, but does not eliminate, the risk of postnatal transmission of HIV. There are currently limited data to guide the optimal frequency of virologic monitoring and the clinical actions to take in case of maternal detectable viral load whilst breastfeeding. Moreover, retention in care and adherence to ART in the postpartum period may be difficult and more research is needed to understand what clinical and psychosocial support would benefit these mothers so that successful engagement in care can be achieved. The long‐term effects of antiretroviral drug exposure in the infants also need further exploration. Thus, there is a need for collecting enhanced surveillance data on WLWH who breastfeed and their infants to augment clinical guidance in high‐income settings.     

Epidemiology and microbiology of subclinical mastitis among HIV-infected women in Malawi

The epidemiology and microbiology of subclinical mastitis, a risk factor for perinatal HIV transmission, have not been well characterized. In all, 250 HIV-infected women were followed from two weeks to 12 months postpartum in Blantyre, Malawi, and subclinical mastitis was assessed by breast milk leukocyte counts. The point prevalence of subclinical mastitis at 2, 4, 6, 10, and 14 weeks, and 6, 9, and 12 months was 12.2%, 7.8%, 6.8%, 3.7%, 10.6%, 5.1%, 4.9%, and 1.9%, respectively (P = 0.002), and 27.2% of women had at least one episode of subclinical mastitis. There was no significant relationship between maternal plasma HIV load or parity and subclinical mastitis. Staphylococcus aureus was isolated in 30% of women with subclinical mastitis, and the proportion of women with positive cultures decreased during follow-up (P = 0.02). Subclinical mastitis is prevalent among breastfeeding mothers and further studies are needed to characterize the differences between infectious and non-infectious subclinical mastitis.     

Longitudinal analysis of human immunodeficiency virus type 1 RNA in breast milk and of its relationship to infant infection and maternal disease

Transmission of human immunodeficiency virus type 1 (HIV-1) via breast-feeding can occur throughout lactation. Defining both fluctuation in breast-milk virus level over time and how breast-milk virus correlates with mother-to-child transmission is important for establishing effective interventions. We quantified breast-milk HIV-1 RNA levels in serial samples collected from 275 women for up to 2 years after delivery. Higher maternal plasma virus load, lower maternal CD4 T cell count, and detection of HIV-1 DNA in maternal genital secretions were significantly associated with elevated breast-milk HIV-1 RNA. Within women who breast-fed, median virus load in colostrum/early milk was significantly higher than that in mature breast milk collected 14 days after delivery (P< or =.004). Breast-feeding mothers who transmitted HIV-1 to their infants had both significantly higher breast-milk viral RNA throughout lactation and more-consistent viral shedding, compared with mothers who did not transmit HIV-1. In breast-feeding women, a 2-fold-increased risk of transmission was associated with every 10-fold increase in breast-milk virus load (95% confidence interval, 1.3-3.0; P<.001). These results indicate that the risk of infant infection from breast-feeding is influenced by breast-milk virus load, which is highest early after delivery.     

Infant feeding practices and attitudes among women with HIV infection in northern Thailand

Knowledge and attitudes towards infant feeding among women in northern Thailand were examined. Face-to-face interviews using structured questionnaires were undertaken in three districts of Chiang Rai province. Subjects included postnatal women with HIV infection (group 1, n=80), antenatal women with HIV infection (group 2, n=36) and antenatal women with unknown HIV status (group 3, n=86). Advantages of breastfeeding and formula feeding according to several characteristics (convenience, cleanliness, cheapness and safety) were rated using a four-point (0-3) scale. Overall, breastfeeding was rated much higher (11.4/12) than formula feeding (6.1/12)(p < 0.0005). Formula feeding rating was highest among postnatal women with HIV infection (6.8/12); however, it was lower than the rating for breastfeeding (11.3/12). The vast majority of women with HIV infection were either formula feeding (group 1, 94%) or intended to formula feed (group 2, 72%) their infants. In contrast, the vast majority of antenatal women of unknown HIV status planned to breastfeed (group 3, 83%). All women, regardless of HIV status, consider breastfeeding to be more advantageous than formula feeding. However, once women with HIV infection are informed of the risk of HIV transmission through breastfeeding, they are able to make their own decision to follow the Thai Ministry of Public Health's recommendation to formula feed.     

Laboratory indicators of mastitis are not associated with elevated HIV-1 DNA loads or predictive of HIV-1 RNA loads in breast milk

BACKGROUND: Mother-to-child transmission (MTCT) of HIV-1 has been associated with symptomatic and asymptomatic mastitis and with the quantity of HIV-1 RNA and DNA in maternal milk. An improved understanding of the relationship between indicators of inflammation and HIV-1 loads in breast milk could improve MTCT prevention strategies. METHODS: In a cross-sectional study, laboratory indicators of mastitis (breast milk sodium [Na(+)] concentration, sodium : potassium ratio [Na(+) : K(+)], and leukocyte count) were related to breast milk HIV-1 RNA and DNA loads and were evaluated for predicting viral loads in milk. RESULTS: Mastitis was present in 63 (15%) of 407, 60 (15%) of 407, and 76 (18%) of 412 milk specimens, as defined by Na(+) concentration >12 mmol/L, Na(+) : K(+) >1, and total leukocyte counts > or =10(6) cells/mL, respectively. Each indicator was associated with an increased milk HIV-1 RNA load (P<.05) but not with HIV-1 DNA load. Neutrophils correlated better with milk HIV-1 RNA load than total leukocytes. However, neither neutrophil count, Na(+) concentration, nor Na(+) : K(+) displayed a threshold that was both sensitive and specific for the detection of HIV-1 RNA in milk at thresholds of > or =50 or > or =10(4) copies/mL. CONCLUSIONS: HIV-1 DNA loads in breast milk were not increased during mastitis. Neither milk cell counts nor electrolyte concentrations were useful predictors of milk HIV-1 RNA or DNA loads for individual women.     

Breastfeeding and chronic HBV infection: clinical and social implications

Mother-to-child transmission of hepatitis B virus (HBV) is among the most important causes of chronic HBV infection and is the commonest mode of transmission worldwide. Currently, the presence of HBsAg, HBeAg and HBV DNA in breast milk is confirmed. Several studies have reported that breastfeeding carries no additional risk that might lead to vertical transmission. Beyond some limitations, the surveys have not demonstrated any differences in HBV transmission rate regarding feeding practices in early childho...     

Association of levels of HIV-1-infected breast milk cells and risk of mother-to-child transmission

Understanding how the level of human immunodeficiency virus type 1 (HIV-1)-infected breast milk cells (BMCs) affects HIV transmission via breast-feeding can shed light on the mechanism of infection and aid in establishing effective interventions. The proportion of infected cells to total cells was measured in serial breast milk samples collected from 291 HIV-1-infected women in Nairobi, Kenya, by use of real-time DNA polymerase chain reaction amplification of BMCs. The number of infected BMCs per million cells was associated with levels of cell-free viral RNA in breast milk (R=.144; P=.032), levels of cell-free virus in blood plasma (R=.365; P<.001), and the detection of proviral DNA in cervical and vaginal secretions (P<.001 and P = .030, respectively). The number of infected BMCs per million cells was lower in colostrum or early milk than in mature milk (P<.001). Previous studies demonstrated that the concentration of BMCs varies throughout lactation, and we used these data to transform infected BMCs per million cells to infected BMCs per milliliter. The estimated concentration of infected BMCs per milliliter was higher in colostrum or early milk than in mature milk (P<.001). Each log10 increase in infected BMCs per milliliter was associated with a 3.19-fold-increased risk of transmission (P=.002), after adjustment for cell-free virus in plasma (hazard ratio [HR], 2.09; P=.03) and breast milk (HR, 1.01; P=1.00). This suggests that infected BMCs may play a more important role in transmission of HIV via breast-feeding than does cell-free virus.     

Field efficacy of zidovudine, lamivudine and single-dose nevirapine to prevent peripartum HIV transmission

OBJECTIVES: In Africa, single-dose nevirapine (NVPsd), short regimens of zidovudine (ZDV) or ZDV + lamivudine (3TC) are recommended to prevent peripartum mother-to-child HIV transmission (PMTCT). We evaluated the 6-week field efficacy of two more PMTCT drug combinations. DESIGN: An open-label intervention cohort in Abidjan. METHODS: In 2001-2002, consenting women started oral ZDV 300 mg twice daily (bid) at > or =36 weeks of gestation, with 600 mg of ZDV + 200 mg NVPsd orally at beginning of labour. In 2002-2003, the antepartum regimen at > or =32 weeks comprised ZDV as previously + 3TC 150 mg bid; the labour dose comprised ZDV + NVPsd as previously + 300 mg 3TC orally. Neonates received ZDV syrup (2 mg/kg per 6 h) for 7 days + NVPsd syrup (2 mg/kg) on day 2 in both periods. Each woman was assisted to either use breast milk substitutes or breastfeed exclusively. Paediatric HIV infection was diagnosed by plasma HIV RNA viral load at 4 weeks, confirmed at 6 weeks. The reference group was a cohort receiving a short regimen of ZDV > or = 36-38 weeks in 1995-2000 in the same population. RESULTS: A total of 1144 HIV-infected pregnant women were included: 351 with ZDV, 420 with ZDV + NVPsd and 373 with ZDV + 3TC + NVPsd; 1010 livebirths were eligible for analysis; 79 children were HIV-infected peripartum. Six-week transmission probability was 6.5% [95% confidence interval (CI), 3.9-9.1%) with ZDV + NVPsd, a 72% reduction compared with ZDV alone (95% CI, 52-88%; P = 0.0002 adjusted on maternal CD4, clinical stage and breastfeeding). It was 4.7% (95% CI, 2.4-7.0%) with ZDV + 3TC + NVPsd (P = 0.34 compared with ZDV + NVPsd). CONCLUSIONS: A short-course of ZDV + NVPsd prevents most peripartum HIV transmission in Africa. This regimen could be added to international guidelines.     

Knowledge of HIV transmission through breast milk among drug-dependent pregnant women

Abstract The current study examined the correlates of knowledge about human immunodeficiency virus (HIV) transmission through breast milk among drug-dependent pregnant women. There is a tremendous need to examine the knowledge about HIV transmission through breastfeeding among this largely understudied, but high-risk subset of pregnant women in order to minimize the extent to which they pass HIV to their children after giving birth. Participants included 97 pregnant women from Baltimore, MD, USA. Prevalence of drug use over the last 6 months included 37.1% reporting smoking marijuana, 36.1% injecting heroin, and 67.0% smoking crack. When asked whether HIV could be transmitted through breast milk, 72 women (74.2%) answered correctly. Our results indicate that the overall knowledge about transmission through breast milk is relatively low. Furthermore, participants who smoked crack during the past 6 months and participants who were white were significantly less likely to have correct knowledge about this topic. Our findings have important implications with regard to preventive interventions for this population. Future research is needed to determine how to best modify these interventions to address the specific needs of drug-dependent pregnant women, and how to specifically target white women and women who smoke crack.