Age-specific prevalence of hepatitis B virus infection in young pregnant women, Hong Kong Special Administrative Region of China.
OBJECTIVE
To investigate the age-specific prevalence of hepatitis B virus (HBV) infection in young pregnant women in Hong Kong Special Administrative Region (SAR), China, and to determine whether an increase in prevalence occurs during adolescence.


METHODS
HBV prevalence was quantified using data from routine antenatal screening for hepatitis B surface antigen (HBsAg) in 10 808 women aged 25 years or younger born in Hong Kong SAR and managed at a single hospital between 1998 and 2011. The effect on prevalence of maternal age, parity and birth before or after HBV vaccine availability in 1984 was assessed, using Spearman's correlation and multiple logistic regression analysis.


RESULTS
Overall, 7.5% of women were HBsAg-positive. The prevalence ranged from 2.3% to 8.4% in those aged ≤ 16 and 23 years, respectively. Women born in or after 1984 and those younger than 18 years of age were less likely to be HBsAg-positive (odds ratio, OR: 0.679; 95% confidence interval, CI: 0.578-0.797) and (OR: 0.311; 95% CI: 0.160-0.604), respectively. For women born before 1984, there was no association between HBsAg carriage and being younger than 18 years of age (OR: 0.60; 95% CI: 0.262-1.370) Logistic regression analysis showed that the prevalence of HBsAg carriage was influenced more by the woman being 18 years old or older (adjusted OR, aOR: 2.80; 95% CI: 1.46-5.47) than being born before 1984 (aOR: 1.42; 95% CI: 1.21-1.67).


CONCLUSIONS
Immunity to HBV in young pregnant women who had been vaccinated as neonates decreased in late adolescence.
Department of Obstetrics and Gynaecology, Chinese University of Hong Kong, Prince of Wales Hospital, Ngan Shing Street, Shatin, New Territories, Hong Kong Special Administrative Region, China .
Terence T
TT
Lao
Department of Obstetrics and Gynaecology, Chinese University of Hong Kong, Prince of Wales Hospital, Ngan Shing Street, Shatin, New Territories, Hong Kong Special Administrative Region, China .
Daljit S
DS
Sahota
Department of Obstetrics and Gynaecology, Chinese University of Hong Kong, Prince of Wales Hospital, Ngan Shing Street, Shatin, New Territories, Hong Kong Special Administrative Region, China .
Lai-Wa
LW
Law
Department of Obstetrics and Gynaecology, Chinese University of Hong Kong, Prince of Wales Hospital, Ngan Shing Street, Shatin, New Territories, Hong Kong Special Administrative Region, China .
Yvonne K Y
YK
Cheng
Department of Obstetrics and Gynaecology, Chinese University of Hong Kong, Prince of Wales Hospital, Ngan Shing Street, Shatin, New Territories, Hong Kong Special Administrative Region, China .
Tak-Yeung
TY
Leung
D000293:Adolescent; D000328:Adult; D005260:Female; D006509:Hepatitis B / Q000453:epidemiology*; D017325:Hepatitis B Vaccines / Q000008:administration & dosage; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D008423:Maternal Age; D010298:Parity; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000453:epidemiology*; D015995:Prevalence
D017325:Hepatitis B Vaccines