Fetal Vascular Lesions Are Increased in Placentas from Women Infected with Pandemic H1N1 Influenza.
Kevin L Tyler, Barbra M Fisher, Virginia D Winn, Anne M Lynch, Janice Scott, Miriam D Post. University of Colorado, Aurora
Background: During the 2009-2010 H1N1 influenza (H1N1) pandemic, the CDC categorized pregnant women as high risk. Complications associated with H1N1 infection included preterm labor, preterm birth, and pregnancy loss, potentially reflecting effects of the H1N1 virus on the placenta. We sought to determine if placentas from women infected with H1N1 during pregnancy showed evidence of increased inflammation, fetal-derived lesions or other placental pathologies.
Design: Women were enrolled under IRB approved protocols who had H1N1 infection during pregnancy confirmed by antigen swab test or PCR. None were acutely infected at the time of delivery. Control subjects were matched for gestational age at delivery, parity and delivery mode. All placentas underwent gross and microscopic pathologic examination and were scored for the presence or absence of inflammation, vascular lesions, meconium and other findings. Fisher's exact test was used for statistical analysis and a p-value of <0.05 was considered significant.
Results: Placentas from H1N1-infected women (n=16) and controls (n=17) were examined. Gestational age (GA) ranged from 35 2/7 to 41 5/7 weeks and placental weights ranged from 330 to 630 grams. To control for GA, the fetal to placental weight ratios were determined and were not different between H1N1 cases and controls (7.28±1.27 vs. 6.89±1.15; p=0.37). No significant differences in inflammation were observed. Acute inflammation of the membranes was seen in 4 H1N1 and 7 control placentas (p=0.46), while chronic membrane inflammation was seen in 2 H1N1 and 1 control placenta (p=0.6). Chronic villitis was observed in 2 H1N1 placentas and 5 controls (p=0.40), while umbilical cord or chorionic plate vascular inflammation was seen in 4 H1N1 placentas and 6 controls (p=0.7). Interestingly, 6 H1N1 placentas had intervillous or subchorionic thrombi, compared to 2 controls (p=0.12) and 3 H1N1 placentas had intimal fibrin cushions compared to 1 control (p=0.11), for an overall occurrence of 9 fetal vascular lesions in H1N1 placentas compared to 3 in controls (p=0.03).
Conclusions: There were no significant differences in maternal inflammation (membranes) or fetal inflammation (umbilical cord and chorionic plate vessels) between the H1N1 and control groups. In contrast, placentas from women infected with H1N1 during pregnancy showed a higher incidence of fetal-derived vascular lesions, suggesting that fetuses exposed to H1N1 may undergo changes that increase risk for vascular lesions.
Category: Gynecologic & Obstetrics
Wednesday, March 2, 2011 9:30 AM
Poster Session V # 126, Wednesday Morning