title: Maternal-fetal microtransfusions and HIV-1 mother-to-child transmission in Malawi.
abstract: BACKGROUND
  Between 25% and 35% of infants born to HIV-infected mothers become HIV-1 infected. One potential route of mother-to-child transmission (MTCT) could be through a breakdown in the placental barrier (i.e., maternal-fetal microtransfusions).
  
  
  RESULTS
  Placental alkaline phosphatase (PLAP) is a 130-kD maternal enzyme that cannot cross the intact placental barrier. We measured PLAP activity in umbilical vein serum as an indicator of maternal-fetal microtransfusion, and related this to the risk of HIV-1 MTCT. A case-cohort study was conducted of 149 women randomly selected from a cohort of HIV-1-infected pregnant Malawians; these women served as a reference group for 36 cases of in utero MTCT and 43 cases of intrapartum (IP) MTCT. Cord PLAP activity was measured with an immunocatalytic assay. Infant HIV status was determined by real-time PCR. The association between cord PLAP activity and HIV-1 MTCT was measured with logistic regression using generalized estimating equations. Among vaginal deliveries, PLAP was associated with IP MTCT (risk ratio, 2.25 per log10 ng/ml PLAP; 95% confidence interval, 0.95-5.32) but not in utero MTCT. In a multivariable model adjusted for HIV-1 RNA load, chorioamnionitis, and self-reported fever, the risk of IP MTCT almost tripled for every log10 increase in cord PLAP activity (risk ratio, 2.87; 95% confidence interval, 1.05-7.83).
  
  
  CONCLUSIONS
  These results suggest that during vaginal deliveries, placental microtransfusions are a risk factor for IP HIV-1 MTCT. Future studies are needed to identify factors that increase the risk for microtransfusions in order to prevent IP HIV-1 MTCT.
authors.affiliation: Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, USA. kwiek@unc.edu
authors.forename: Jesse J
authors.initials: JJ
authors.lastname: Kwiek
authors.forename: Victor
authors.initials: V
authors.lastname: Mwapasa
authors.forename: Danny A
authors.initials: DA
authors.lastname: Milner
authors.forename: Alisa P
authors.initials: AP
authors.lastname: Alker
authors.forename: William C
authors.initials: WC
authors.lastname: Miller
authors.forename: Eyob
authors.initials: E
authors.lastname: Tadesse
authors.forename: Malcolm E
authors.initials: ME
authors.lastname: Molyneux
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Rogerson
authors.forename: Steven R
authors.initials: SR
authors.lastname: Meshnick
mesh_terms: D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood* / Q000378:metabolism; D015331:Cohort Studies; D036861:Delivery, Obstetric / Q000379:methods; D005260:Female; D005312:Fetal Blood / Q000201:enzymology; D015658:HIV Infections / Q000635:transmission* / Q000821:virology; D015497:HIV-1 / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D018445:Infectious Disease Transmission, Vertical; D008295:Malawi; D010920:Placenta / Q000201:enzymology; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000821:virology*; D012367:RNA, Viral / Q000097:blood*; D012307:Risk Factors; D019562:Viral Load
chemical_list: D012367:RNA, Viral; D000469:Alkaline Phosphatase