ABSTRACT Objective To evaluate the impact of screening and treating asymptomatic pregnant women for C. trachomatis and N. gonorrhoeae infections on the frequency of preterm birth or low birth weight infants in Botswana. Design Non-randomized, cluster-controlled trial. Setting Four antenatal care clinics in Gaborone, Botswana. Population Pregnant women aged ≥15 years, attending a first antenatal care visit, ≤27 weeks gestation, and without urogenital symptoms were eligible. Methods Participants in the intervention clinics received screening (GeneXpert®, Cepheid) during pregnancy and at the post-natal visit. Participants in the standard-of-care clinics received screening at the postnatal visit only. We used multivariable logistic regression and post-estimation predictive margins analysis. Post-hoc analysis was conducted among sub-samples stratified by parity. Main outcome measures Preterm birth (<37 weeks gestation) and low birth weight (<2500g). Results After controlling for parity, hypertension, antenatal care visits, and clinic site, the predicted prevalence of preterm or low birth weight was lower in the intervention arm (11%) compared to the standard-of-care (16%) (AOR: 0.59; 95% CI: 0.28 to 1.24), but confidence intervals were wide. In post-hoc analysis, the intervention was more effective than the standard-of-care (AOR: 0.20; 95% CI: 0.07-0.64) among nulliparous participants. Conclusion A C. trachomatis and N. gonorrhoeae infection screening and treatment intervention among asymptomatic pregnant women did not significantly reduce preterm or low birth weight outcomes. Post hoc analysis found the intervention reduced adverse outcomes among nulliparous participants.