Introduction:
Good knowledge of prevention of mother-to-child transmission (PMTCT) can improve mothers’ behavior in seeking care. This study aimed to assess knowledge on PMTCT, human immunodeficiency virus (HIV), and acquired immunodeficiency syndrome (AIDS) at three public antenatal clinics in Maputo City.

Material and methods:
Between December 2013 and November 2014, an antenatal care (ANC)/PMTCT cross-sectional exit survey among pregnant women was conveniently conducted. Face-to-face interviews, adjusted odds ratios, and 95% confidence intervals were applied.

Results:
In total, 420 pregnant women were enrolled into the study, and 72.7% had high PMTCT knowledge, 72% knew mother-to-child transmission (MTCT) can occur in pregnancy, 76.4% through breastfeeding, 82.9% in labor, and 92.7% knew drugs to reduce MTCT. Similarly, 83.4% had high HIV prevention knowledge. PMTCT knowledge was more likely to increase with age (AOR = 3.83; 95% CI: 1.36-10.81) and education (AOR = 2.16; 95% CI: 1.15-4.08). HIV prevention knowledge was likely to increase with education (AOR = 4.71; 95% CI: 1.54-14.36), being married (AOR = 2.66; 95% CI: 1.30-5.43), and through condom use (AOR = 2.16; 95% CI: 1.13-4.14).

Conclusions:
Most pregnant women had high PMTCT and HIV prevention knowledge. The youngest, single, and illiterate women have challenges to access information. PMTCT education in verbal mother tongue is required due to limited literacy. Male partner involvement should be strongly supported.