Despite the success of Vietnam's national childhood vaccination program for over 30 years, whooping cough remains a dangerous disease, especially for infants under three months old. A protective cocoon vaccination strategy is important to reduce the disease burden of pertussis in Vietnam. The Viet Nam Association of Preventive Medicine (VAPM) and the Viet Nam Association of Gynecology and Obstetrics (VAGO) have reached a consensus on recommending Tetanus – diphtheria – pertussis (Tdap) vaccination during pregnancy. This is because Tdap vaccination in the second and third trimesters has been found to be safe and offers significant benefits in preventing tetanus, diphtheria, and pertussis for mothers and infants throughout pregnancy. However, pending official regulatory guidance from the Ministry of Health, many obstetricians and obstetric hospitals remain hesitant to administer Tdap vaccinations to pregnant women. University Medical Center of Ho Chi Minh City is one of the few pioneering hospitals to vaccinate pregnant women with the Tdap vaccine at the hospital's vaccination unit since the vaccine Boostrix (GSK) became available in the Vietnamese market in 2021. A cross-sectional study analyzing two hundred eighty-six pregnant women was conducted to assess their knowledge levels and factors influencing vaccination decisions. Results showed that more than half of the pregnant women had received advice about vaccines from their doctors. Nearly 40% of pregnant women refuse to be vaccinated with Tdap due to significant concerns about side effects and adverse effects on the fetus. Knowledge about the Tdap vaccine was moderate (7.234/15), with most incorrect answers related to vaccine safety. Notably, the odds of accepting vaccination doubled (OR = 2.04; 95%CI:1.21- 3.44) if a doctor's consultation occurred. These findings underscore the importance of healthcare professionals in providing vaccination counseling during pregnancy, as it significantly increases vaccine coverage rates and ultimately optimizes newborn protection against pertussis. Widespread implementation within the fields of obstetrics and preventive medicine in Vietnam is recommended.