This is an open-label randomized control trial and feasibility study designed to determine the feasibility of a larger RCT in our setting that would examine prenatal probiotic use in Group B Strep (GBS) positive pregnant women at term. Investigators hope to address the question of whether prenatal oral probiotic use, taken by healthy low risk GBS positive women from approximately 37 weeks gestation until the time of birth, will reduce the number of women who test positive for GBS at the time of admission to Labor and Delivery (L&D).

This is an open-label randomized control trial and feasibility study designed to determine the feasibility of a larger RCT in our setting that would examine prenatal probiotic use in Group B Strep (GBS) positive pregnant women at term. We hope to address the question of whether prenatal oral probiotic use, taken by healthy low risk GBS positive women from approximately 37 weeks gestation until the time of birth, will reduce the number of women who test positive for GBS at the time of admission to Labor and Delivery (L&D). In this study we aim to determine whether such a study is acceptable in our population, whether any adverse events are identified, and what barriers or confounding variables might exist to probiotic use at term. We will also look at whether probiotic use had any reported effect on maternal gastrointestinal (GI) symptoms.

Inclusion Criteria:

• Healthy adult (≥ 18 years of age) pregnant women who are 36 - 37 6/7 weeks gestation at enrollment [calculated from the first day of Last Normal Menstrual Period (LNMP) and/or ultrasound (US)]

Group B Streptococcus Positive at 36 weeks gestation with:

• No obstetric complication requiring delivery prior to 39 weeks (hypertensive disorder diagnosed prior to enrollment, gestational diabetes, multiple gestation)
• No fetal complication (e.g., birth defect, intrauterine growth restriction)
• No medical complication (e.g., chronic hypertension, preexisting diabetes mellitus)
• Who do not currently ingest an over the counter probiotic supplement (not including yogurt)
• Who can both speak and read English or Spanish
• Pregnant women who regularly attend UNM prenatal clinics for their prenatal care ("regularly attend" will be defined as starting prenatal care prior to 20 weeks gestation and missing no more than one prenatal appointment during this pregnancy)
• No hypersensitivity reaction to β-lactam antibiotics

Exclusion Criteria:

• Those less than 18 years of age
• Non-pregnant women
• Later in pregnancy than 38 weeks gestation at enrollment [per LNMP and/or US]
• Those with an obstetric, fetal or medical complication of pregnancy
• Group B Streptococcus negative at 36 weeks gestation. Those ineligible for testing at 36 weeks gestation (history of GBS bacteriuria during the current pregnancy or have previously given birth to a GBS affected child.) We will not exclude those with bacteriuria other than GBS, and we will not exclude women who have taken an antibiotic during pregnancy, but we will track this as it is addressed in the Questionnaire for Women.
• Women who are currently ingesting an over the counter probiotic supplement (except for yogurt)
• Women who do not have electricity in the home.
• Women who are planning an elective repeat cesarean birth
• Women who do not speak and read English or Spanish
• Women with a history of missing one or more scheduled prenatal visit during this pregnancy
• Hypersensitivity reaction to β-lactam antibiotics

T1 (baseline; 36.0-37.6 weeks) through T5 (6 week postpartum visit; up to 12 weeks and 6 days from baseline)

We did not find any reports of adverse events in our study participants.

Participants and researchers were not masked to group assignment which may have led to unintended biases in responses and interpretation of questionnaires. Several IP samples were missed. The COVID-19 pandemic limited recruitment and may have prevented recruitment of those who would otherwise have participated. There were significant problems with laboratory processing of IP GBS swabs, resulting in 23 laboratory samples not being analyzed.