Background: Behavioral and social changes in the modern era have triggered an increase in the incidence of early sexual contact and teenage pregnancy. Since there is no routine Gonococcal & Chlamydial (GC & CT) screening in teens in antenatal clinics in Thailand, the present study was performed to find the prevalence of STI, especially Chlamydial infection, in teenage pregnancy.
Objective: To evaluate the prevalence of sexually transmitted infections (STIs), especially Chlamydial infection (CT), in
teenage pregnancy and its related factors.
Material and Method: One hundred and twenty-one teenage pregnancies were recruited at the ANC in Rajavithi Hospital
from October 2006 to May 2007. After signing informed consent forms, they were asked to answer questionnaires about baseline data, sexual information and risk factors, after which urine specimens were collected for screening for GC and CT using the PCR technique (AMPLICOR by Roche). Later, pelvic examination was performed by the gynecologist at the STD (sexually transmitted disease) clinic. All the data and LAB results were recorded and analyzed by the SPSS program. Numbers, percentages, means with SD, Chi-squared test, Fisher’s exact test and odds ratio were used. Potential risk factors were analyzed using binary logistic regression.
Results: The prevalence of STI in pregnant teenagers was 28.1% (CT = 19.8%, GC = 1.7%, hepatitis B = 3.3%, trichomoniasis 1.7%, Herpes simplex = 0.8% and condyloma acuminata = 0.8%). No Syphilis, chancroid or HIV were found in the present study. Other non-STI like candidiasis and bacterial vaginosis were found in 45.5% of participants (candidiasis and bacterial vaginosis at 19.0% and 24.8%, respectively). The risk of CT infection was significantly related (6.9 times higher) to having previous sexual contact before the current partner (95% CI, 1.8-27.0).
Conclusion: STI, especially Chlamydial infection, was found in a significant number of teenage pregnancies. Measures should be taken to prevent this resulting in complicated outcomes in the future.

Keywords: Prevalence, Sexually transmitted infection, Teenage pregnancy, Chlamydial infection