title: Higher in utero and perinatal HIV infection risk in girls than boys.
abstract: OBJECTIVE
  This study analyzed mother-to-child HIV transmission rates by sex and exposure time for babies born to HIV-infected, untreated African women.
  
  
  METHODS
  Data were analyzed from 2 independent studies done in Malawi during the 1990s. Infections were established by polymerase chain reaction on blood samples. Odds ratios (ORs) for transmission were examined by period at risk: in utero (infected in umbilical cord blood), perinatal (infected in 1st postnatal blood > or =4 weeks), and postnatal (later postnatal infection).
  
  
  RESULTS
  Among 1394 singleton births, girls were more likely to become infected than boys. For in utero transmission, the OR was 1.4 (95% CI: 0.9 to 2.2). For transmission during early life (umbilical cord blood not available) the OR was 2.7 (95% CI: 1.5 to 4.9). However, transmission risks in the perinatal and postnatal infection periods did not differ in boys and girls. Among 303 tested twin-birth pairs, girls were at higher risk than boys for in utero (OR: 2.6; 95% CI: 1.2 to 5.8) and perinatal (OR: 1.9; 95% CI: 1.0 to 3.7) infection. Recognized mother-to-child transmission risk factors did not explain the higher risk of infection in girls.
  
  
  CONCLUSIONS
  Girls were at higher risk of early (in utero and perinatal) HIV infection than boys. It is proposed that minor histocompatibility reactions between maternal lymphocytes and infant Y chromosome-derived antigens reduce the risk of HIV transmission in boys.
authors.affiliation: Viral Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Division of Health and Human Services, Bethesda, MD, USA. biggarb@mail.nih.gov
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Biggar
authors.forename: Taha E
authors.initials: TE
authors.lastname: Taha
authors.forename: Donald R
authors.initials: DR
authors.lastname: Hoover
authors.forename: Francis
authors.initials: F
authors.lastname: Yellin
authors.forename: Newton
authors.initials: N
authors.lastname: Kumwenda
authors.forename: Robin
authors.initials: R
authors.lastname: Broadhead
mesh_terms: D004198:Disease Susceptibility; D005260:Female; D006678:HIV / Q000235:genetics; D015658:HIV Infections / Q000453:epidemiology / Q000635:transmission*; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D018445:Infectious Disease Transmission, Vertical; D008295:Malawi; D008297:Male; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious; D012367:RNA, Viral / Q000097:blood; D012307:Risk Factors; D012727:Sex Characteristics; D013223:Statistics as Topic
chemical_list: D012367:RNA, Viral