Introduction: The investigation of systematic screening for asymptomatic genital infections in pregnant women is justified by the relevance of these conditions in determining adverse neonatal outcomes, such as prematurity, low birth weight, and perinatal morbidity and mortality. Despite its importance, previous studies have shown inconsistent results, largely due to methodological limitations related to sample size, lack of standardized treatment protocols, and insufficient follow-up of pregnant women. There is also divergence among national and international guidelines, which vary between universal and selective recommendations, highlighting gaps in the standardization of clinical practices.

Objectives: To investigate the effectiveness of implementing systematic screening protocol for asymptomatic genital infections in pregnant women in preventing adverse gestational and neonatal outcomes. The specific objectives are: to identify the most prevalent infections in this group; to evaluate the relationship between treatment and the incidence of complications; to compare outcomes between participants assigned to systematic screening and those receiving standard care and to propose recommendations for clinical practice and health policies based on a critical review of the literature and the results obtained.

Methods: This is a randomized controlled trial that will recruit 250 pregnant women, followed from the first trimester until delivery. Participants will be randomized into two groups: an intervention group, undergoing systematic screening with protocol-guided treatment, and a control group, managed according to current standard care practices, following the municipality's protocol for screening and treatment of genital infections. Primary outcomes include preterm birth, preterm premature rupture of membranes, low birth weight, intra-amniotic infection, puerperal infection, neonatal infection, and fetal and neonatal mortality. Statistical analysis will follow the intention-to-treat principle, and differences in outcomes between groups will be estimated.

Expected Results: This study is expected to provide evidence on whether systematic screening reduces (or does not reduce) maternal and neonatal complications. The randomized controlled trial will be prospectively registered prior to the enrollment of the first participant, in accordance with current ethical standards.

** The study has not started yet and no participants have been enrolled. The term "low-risk" was removed because the study will recruit pregnant women in general

This randomized controlled trial will evaluate whether systematic microbiological screening and protocol-based treatment of asymptomatic lower genital tract infections during pregnancy can reduce adverse gestational and neonatal outcomes among low-risk pregnant women.

The study will be conducted in Uruguaiana, a municipality in southern Brazil, within the municipal prenatal care network. Pregnant women receiving care through the Family Health Strategy will be referred to a Women's Health referral service and followed from first-trimester enrollment until delivery. The study is linked to the Graduate Program in Pathology at São Paulo State University "Júlio de Mesquita Filho" (UNESP), Botucatu Medical School.

Participants will be randomized in a 1:1 allocation ratio to either an experimental arm or an active comparator arm. The random allocation sequence will be generated electronically and managed by a designated nursing technician. The physician responsible for clinical care will not have prior access to the allocation sequence, and group assignment will be revealed only after participant enrollment, in order to preserve allocation concealment.

Participants assigned to the experimental arm will undergo enhanced microbiological screening during prenatal follow-up. Vaginal samples will be collected at scheduled prenatal visits for Gram stain-based evaluation of vaginal microbiota. Endocervical samples will be collected once per trimester for real-time polymerase chain reaction detection of Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium, and Trichomonas vaginalis. Samples positive for Mycoplasma genitalium will undergo additional analysis for 23S rRNA gene mutations associated with macrolide resistance. Vaginal and cervical infections identified during follow-up will be managed according to a predefined study protocol based on current clinical guidelines.

Participants assigned to the active comparator arm will receive standard prenatal care according to the current municipal clinical protocol. In this group, screening for Chlamydia trachomatis and Neisseria gonorrhoeae will be performed during the first trimester only for pregnant women younger than 30 years, as established by the municipal protocol. Management of vulvovaginal infections will be based on clinical criteria, and treatment will follow the standard municipal protocol.

Study data will be obtained from clinical interviews, biological sample collection, laboratory testing, and review of maternal and neonatal medical records. Clinical interviews will collect sociodemographic, obstetric, and relevant clinical information. Vaginal samples will be analyzed by Gram staining and classified according to predefined microbiological criteria. Endocervical samples will be processed for molecular detection of selected sexually transmitted pathogens. Neonatal and delivery-related outcomes will be collected through review of hospital medical records after delivery at the reference maternity hospital.

All study procedures will be performed by trained personnel in appropriate clinical settings and in accordance with biosafety standards. No additional blood samples will be collected exclusively for research purposes; blood tests will be limited to those routinely performed during prenatal care according to current Brazilian Ministry of Health guidelines.

Participants in both groups will be followed until delivery. The study will compare maternal, obstetric, and neonatal outcomes between the experimental and active comparator groups. Data will be recorded using standardized electronic case report forms and stored in an anonymized electronic database with restricted access to authorized research personnel.

The statistical analysis will follow the intention-to-treat principle, with participants analyzed according to their originally assigned groups, regardless of adherence to the assigned protocol. Categorical variables will be described using absolute and relative frequencies, and continuous variables will be summarized using measures of central tendency and dispersion, as appropriate. Between-group comparisons will be performed using suitable statistical tests according to variable type and distribution. Logistic regression models may be used to estimate the association between the intervention and study outcomes, adjusting for potential confounding variables when applicable. Results will be reported with effect estimates and 95% confidence intervals.

The study will be conducted in accordance with the Declaration of Helsinki and applicable Brazilian regulations for research involving human participants. Written informed consent will be obtained before enrollment. For participants younger than 18 years, written informed consent will be obtained from a legal guardian, and assent will be obtained from the minor participant. Participant confidentiality and data protection will be ensured in accordance with the Brazilian General Data Protection Law.

** The study has not started yet and no participants have been enrolled. The term "low-risk" was removed because the study will recruit pregnant women in general

Inclusion Criteria:

• First-trimester pregnant women.
• Receiving care at the Women's Health service.
• Willingness to participate in the study.

Exclusion Criteria:

#No specific exclusion criteria.

The study has not started yet and no participants have been enrolled. The term "low-risk" was removed because the study will recruit pregnant women in general

Individual participant data will not be shared publicly. Requests for additional information may be evaluated by the study team according to ethical and institutional regulations.