There were higher odds of first in utero 3TC and ZDV/3TC exposure in the third trimester among cases than non-cases in unadjusted analyses (Table 4). When adjusted for year of birth, the odds of first exposure to 3TC and to ZDV/3TC in the third trimester were higher in cases than non-cases (3TC: OR, 10.57; 95% CI, 1.93–75.61; ZDV/3TC: OR, 9.84; 95% CI, 1.77–71.68). However, no significant association was detected for first exposure to ZDV alone in the third trimester (OR, 1.72; 95% CI, 0.30–12.17). In secondary analyses where all 42 possible cases and all non-cases were included (Fig. 1), the adjusted ORs were 2.95 (95% CI, 0.91–10.90) and 3.46 (95% CI, 1.09–12.61) for overall in utero exposure to 3TC and to ZDV/3TC, respectively and 5.87 (95% CI, 1.61–22.31) and 5.59 (95%CI, 1.52–21.42) for first in utero exposure to 3TC and to ZDV/3TC in the third trimester, respectively.
The six cases first exposed to 3TC in the third trimester (Table 4) also were first exposed to ZDV/3TC in the third trimester; three had prior exposure to ZDV alone in the first or second trimester with initiation of 3TC in the third trimester. Although not statistically significant, peak maternal viral loads in the third trimester were higher among five cases first exposed to ZDV/3TC in the third trimester (maternal viral load was unavailable for one of the six cases) than among non-cases and cases with other distributions of in utero NRTI exposure (median log10 HIV RNA copies/mL 4.0 versus 3.4 and 2.9, respectively); and a higher proportion of the six cases was exposed to psychoactive drugs in utero (33.3% versus 15.9% and 7.1%, respectively). Psychoactive drug exposure, excluding alcohol, was higher in the three ARV unexposed cases than in non-cases and exposed cases.
Clinical manifestations associated with MD appear to occur more frequently in infants born of HIV-infected women than in the general pediatric population, and there is some evidence that this may be due to in utero NRTI exposure ; non-human studies also support a possible etiologic association [21–23]. We did not observe a significant association between overall in utero NRTI exposure and clinical manifestations suggestive of possible MD. However, increased odds of first in utero 3TC and of first in utero ZDV/3TC exposure in the third trimester among HIV-uninfected children with signs consistent with possible MD were identified. We were unable to distinguish whether the increased odds was due to 3TC or to ZDV/3TC.
Others also have reported the occurrence of possible or definite MD associated with initiation of maternal ARV late in pregnancy. An American infant with confirmed MD first exposed to ZDV/3TC and nevirapine at 33 weeks' gestation had no identified genetic or virologic predisposition to MD other than in utero NRTI exposure . In addition, three of eight cases of MD in the EPF initial case series also were first exposed to ZDV/3TC in the third trimester, and another case was first exposed to ZDV in the third trimester . First exposure to 3TC and to ZDV/3TC in the third trimester may lead to MD in some children; all but one of our possible cases had neurological signs of MD. Studies of antiepileptic drug use during pregnancy have suggested that in utero exposure during the third trimester may partially account for the intellectual impairment and decreased head circumference observed in exposed children [24,25]. In our study only first exposure to 3TC or ZDV/3TC in the third trimester was significantly associated with possible MD; no significant association was detected for first exposure to 3TC or ZDV/3TC in the first or second trimester. Due to the limited use of other ARV in combination, we cannot rule out an etiologic association of other combinations and timings of in utero NRTI exposure and possible MD. Further, the CI of our estimates are wide due to the small number of cases.
It is possible that late initiation of ARV in the pregnant mother is confounded by other determinants of fetal injury. In utero cocaine exposure has been associated with cognitive impairments  and cardiovascular abnormalities , conditions included in our case definition. A study of the neurodevelopment of HIV-uninfected children exposed to ARV in utero and of HIV and ARV-unexposed children demonstrated a strong association between in utero exposure to cocaine, heroin, and tobacco exposure and low developmental scores . Poor access to ARV, which may relate to late prenatal care, has also been observed in drug users . We were unable to control adequately for psychoactive drug exposure, and we did not have data on timing of initiation of prenatal care. None of the children with MD in the EPF were exposed to illicit psychoactive drugs in utero .
The association between first exposure to 3TC in the third trimester and possible MD may be confounded by high maternal viral loads, which were observed among some of our cases first exposed to 3TC, and to ZDV/3TC, in the third trimester. A proposed mechanism may be a high level of cytokines in women with more advanced HIV disease and late ARV initiation; these cytokines may adversely affect placental function and injure the fetus. In addition, there is evidence that HIV-uninfected infants born of HIV-infected women have depletions in mitochondrial DNA in the absence of in utero ARV exposure .
Seventeen (1.8%) of 933 in utero NRTI exposed children included in our primary analysis met the EPF definition of possible MD, which is six times higher than the rate of MD of 0.3% observed among in utero NRTI exposed children in the EPF . Three children without in utero ARV exposure had clinical manifestations of possible MD; our rate of possible MD in the NRTI-unexposed children was 2.9% versus 0% in the EPF cohort . Our cases were identified through retrospective review of clinical signs, which likely has poor positive predictive value . Unlike the EPF study, we did not have mitochondrial histological or enzymological studies or cerebral magnetic resonance imaging necessary for more definitive case identification. In an effort to reduce misclassification we excluded children whose only sign of MD was cognitive developmental delay – children whom the reviewing clinicians were less confident classifying as possible cases – from our primary analysis, and indeed, the estimated ORs were increased from those estimated when all cases were included. Our cases are perhaps best described as having a constellation of signs with unexplained etiology that could be consistent with MD according to the EPF criteria. In addition, our cases had abnormalities evident before 3 years of age and cases with later presentation of abnormalities were not included.
The higher odds of first exposure to 3TC, and to ZDV/3TC, were driven by six cases born in 1996, 1997, and 1999. Although we cannot explain the temporality of our findings, consistent results were obtained with various parameterizations of year of birth. A small proportion of HIV-uninfected children born of HIV-infected women in the USA enrolled in protocols 219 and 219C, and we cannot assess whether there was selective enrollment with respective to in utero NRTI exposure and/or possible signs of MD. Selection bias also could have arisen from differential discontinuation of follow-up.
The male predominance among our cases is concordant with previous reports. Only three of 12 cases reported in the EPF study were female (S. Blanche, personal communication 2005). A study of genetic mitochondrial disorders in the general pediatric population also demonstrated a male predominance (58% versus 42%) .
In summary, we did not observe an association between overall in utero ART exposure and possible MD. We did observe higher odds of first in utero exposure to 3TC, and to ZDV/3TC, in the third trimester among HIV-uninfected children with unexplained signs consistent with possible MD. This may demonstrate an etiologic association between third trimester initiation of certain NRTI and MD. Alternatively, our findings may be confounded by other causes of fetal injury such as higher maternal HIV RNA levels, psychoactive drug exposure, or late prenatal care. ARV prophylaxis is a critical component of the prevention of MTCT of HIV infection as recommended by the US Public Health Service . The benefits of ARV prophylaxis outweigh any known risks to date. Many ARV drugs and therapeutic classes are available, and it is important to identify particular drugs or combinations that confer greater or lesser risk to the developing fetus. Additional studies that rigorously assess MD and allow for better control of confounding are needed.
We thank the children and families for their participation in PACTG 219 and 219C, and the individuals and institutions involved in the conduct of 219C. We would like to acknowledge PACTG protocols 076, 082, 185, 249, 250, 255, 316, 332, 353, 354, 358, and 386, which collected some of the data used in this study.
Sponsorship: The study was funded by the United States National Institute of Allergy and Infectious Diseases, and the National Institute of Child Health and Human Development. This work was supported by the Statistical and Data Analysis Center (SDAC) of the Pediatric AIDS Clinical Trials Group at Harvard School of Public Health, under the National Institute of Allergy and Infectious Diseases cooperative agreement No. 5 U01 AI41110.
Participants in the PACTG Protocol 219C
Baylor Texas Children's Hospital: F Minglana, ME Paul, CD Jackson; University of Florida, Jacksonville: MH Rathore, A Khayat, K Champion, S Cusic; Chicago Children's Memorial Hospital: R. Yogev, E. Chadwick; University of Puerto Rico, University Children's Hospital AIDS Program: I. Febo-Rodriguez, S. Nieves; Bronx Lebanon Hospital Center; M Purswani, S Baksi, E Stuard, M Dummit; San Juan Hospital: M Acevedo, M Gonzalez, L Fabregas, ME Texidor; University of Miami: GB Scott, CD Mitchell, L Taybo, S Willumsen; University of Medicine & Dentistry of New Jersey: L Bettica, J Amour, B Dashefsky, J Oleske; Charity Hospital of New Orleans & Earl K. Long Early Intervention Clinic: M Silio, T Alchediak, C Boe, M Cowie; UCSD Mother, Child & Adolescent HIV Program: SA Spector, R Viani, M Caffery, L Proctor; Howard University: S Rana, D Darbari, JC Roa, PH Yu; Jacobi Medical Center: M Donovan, R Serrano, M Burey, R Auguste; St. Christopher's Hospital for Children, Philadelphia: J. Chen, J. Foster; Baystate Medical Center Children's Hospital: BW Stechenberg, DJ Fisher, AM Johnston, M Toye; Los Angeles County Medical Center/USC: J Homans, M Neely, LS Spencer, A Kovacs; Children's Hospital Boston:S Burchett, N Karthas; Children's Hospital of Michigan: E. Moore, C. Cromer; St. Jude Children's Research Hospital, Memphis: PM Flynn, N Patel, M Donohoe, S Jones; New York University School of Medicine/Bellevue Hospital: W Borkowsky, S Chandwani, N Deygoo, S Akleh; The Children's Hospital at Downstate: E Handelsman, HJ Moallem DM Swindell, JM Kaye; The Columbia Presbyterian Medical Center & Cornell University New York Presbyterian Hospital: A Higgins, M Foca, P LaRussa, A Gershon; The Children's Hospital of Philadelphia: RM Rutstein, CA Vincent, SD Douglas, GA Koutsoubis; Children's Hospital of Oakland: A Petru, T Courville; UCSF, Moffitt Hospital: D Wara, D Trevithick; Children's Hospital, University of Colorado, Denver: E. McFarland, C. Salbenblatt;Johns Hopkins University Pediatrics: N Hutton, B Griffith, M Joyner, C Kiefner; Children's Hospital and Regional Medical Center, Washington: M Acker, R Croteau, C McLellan, K Mohan; Metropolitan Hospital Center: M. Bamji, I. Pathak, S. Manwani, E. Patel; Children's National Medical Center: H. Spiegel, V. Amos; University of Massachusetts Medical School: K Luzuriaga; University of Alabama at Birmingham:R Pass, M Crain; University of Maryland Medical Center: J Farley, K Klipner; Schneider Children's Hospital: VR Bonagura, SJ Schuval, C Colter, L Campbell; Boston Medical Center: SI Pelton, AM Reagan; University of Illinois: KC Rich, K Hayani, M Bicchinella; SUNY Stony Brook: S Nachman, D Ferraro, S Madjar; North Broward Hospital District: A. Puga; Duke University: F Wiley, K Whitfield, O Johnson, R Dizney; Harlem Hospital: S Champion, M Frere, M DiGrado, EJ Abrams; Cook County Hospital: J. Martinez; University of South Alabama: M Mancao; Connecticut Children's Medical Center: J. Salazar, G. Karas; University of North Carolina at Chapel Hill: T Belho, B Pitkin, J Eddleman; Ruiz Arnau University Hospital: W. Figueroa, E. Reyes; SUNY Upstate Medical University: LB Weiner, KA Contello, WA Holz, MJ Famiglietti; Children's Medical Center of Dallas; University of Florida at Gainesville: R Lawrence, J Lew, C Delany, C Duff; Children's Hospital at Albany Medical Center: AD Fernandez, PA Hughes, N Wade, ME Adams; Lincoln Medical & Mental Health Center; Phoenix Children's Hospital: JP Piatt, J Foti, L Clarke-Steffen; Public Health Unit of Palm Beach County: J. Sleasman, C. Delaney; Medical College of Georgia: CS Mani; Yale University School of Medicine: WA Andiman, S Romano, L Hurst, J de Jesus; Vanderbilt University Medical Center: G Wilson; University of Rochester Medical Center: GA Weinberg, F Gigliotti, B Murante, S Laverty; St. Josephs Hospital and Medical Center, New Jersey: N. Hutchcon, A. Townley; Emory University Hospital: S. Nesheim, R. Dennis; University of South Florida: P Emmanuel, J Lujan-Zilberman, C Graisberry, S Moore; Children's Hospital of the King's Daughters: RG Fisher, KM Cunnion, TT Rubio, D Sandifer; Medical University of South Carolina: GM Johnson; University of Mississippi Medical Center: H. Gay, S. Sadler; Harbor-UCLA Medical Center: M Keller, J Hayes, A Gagajena, C Mink; Mount Sinai Medical Center: D. Johnson; Children's Hospital of Los Angeles: J. Church, T. Dunaway, C. Salata; Long Beach Memorial: A. Deveikis, L. Melton; Robert Wood Johnson Medical School: S Gaur, P Whitley-Williams, A Malhotra, L Cerracchio; Sinai Children's Hospital: M Dolan, J D'Agostino, R Posada; The Medical Center, Pediatric Columbus, Georgia: C. Mani, S. Cobb; Medical College of Virginia: SR Lavoie, TY Smith; Cooper Hospital - University Medical Center: A. Feingold, S. Burrows-Clark; University of Cincinnati: J. Mrus, R. Beiting; Columbus Children's Hospital: M Brady, J Hunkler, K Koranyi; Sacred Heart Children's CMS of Florida: W. Albritton; St. Luke's/Roosevelt Hospital Center: R Warford, S Arpadi; Incarnation Children's Center, New York: A. Gershon, P. Miller; Montefiore Medical – AECOM: A. Rubinstein, G. Krienik; Children's Hospital of Los Angeles: A. Kovacs and E. Operskalski; San Francisco General Hospital: D. Wara, A. Kamrin, S. Farrales; Cornell University New York Presbyterian: R. Johan-Liang, K. O'Keefe; St. Louis Children's Hospital: KA McGann, L Pickering, GA Storch; North Shore University Hospital: S. Pahwa, L. Rodriquez; Oregon Health and Science University: P. Lewis, R. Croteau.
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Keywords:© 2007 Lippincott Williams & Wilkins, Inc.
Children; HIV; mitochondria; zidovudine; lamivudine; pregnancy toxicity