Viral Load of Human Papillomavirus (HPV) During Pregnancy and Its Association With HPV Vertical Transmission

Little is known on the dynamics of human papillomavirus (HPV) viral load during pregnancy and on the impact of viral load on HPV vertical transmission. We described viral loads for several genotypes during pregnancy and analyse its association with vertical transmission. Data were analysed from the HERITAGE study, a cohort of pregnant women recruited between 2010 and 2016 in three centres in Canada. Vaginal samples were collected at the first and third trimesters of pregnancy, placental samples were collected at birth, and conjunctival, oral, pharyngeal, and genital samples were collected in children at birth and 3 months were tested for HPV DNA and viral load by Linear Array essay. The association between viral load and vertical transmission was measured using logistic regression. Odd ratios (ORs) and their 95% Confidence intervals (CI) were adjusted for age of the mother. We included women in the cohort infected with the 13 most common genotypes during pregnancy (n = 287). A decrease in HPV viral load was observed during pregnancy (median difference between the third and first trimester of pregnancy = -0.005 copies/cell [p < 0.05]). Women with more than 2 HPV copies/cell (compared to those with <= 2 copies) at first trimester had a statistically significant higher risk of vertical transmission (adjusted OR = 6.41; 95% CI: 1.10-37.34 for any genotypes and OR = 17.17; 95% CI: 1.18-250.28 for HPV-16). Viral load values analysed continuously or categorized with different cut-offs showed comparable results. HPV viral load varied during pregnancy and was strongly associated with HPV vertical transmission. The results provide a better understanding of risk factors associated with vertical transmission.