Modifying Progesterone and Estradiol Levels to Prevent Postpartum Cigarette Smoking Relapse and Reduce Secondhand Smoke Exposure in Infants and Children

The investigators aim to address the following specific aims: * Determine the efficacy of Prog in preventing postpartum smoking relapse and reducing smoking relapse risk factors. * Examine the effects of this maternal smoking intervention on infant health. * Examine racial and ethnic differences in intervention outcomes.

Inclusion Criteria: * Ability to provide informed consent, * Aged 18 to 45 years old * Self-reported stable physical and mental health 1. self-report uncomplicated pregnancy at gestational week 30 or beyond, or 2. self-report the birth of a child within the past 6 months * History of ≥ 4 cigarettes per month during the six months prior to pregnancy * At enrollment, self-report of motivation to become and/or remain abstinent after delivery ≥ 6 on a 10 point Likert-type scale * Willingness to protect against pregnancy following day 0 to week 12 of the study * Participants must live in the continental US and have a device to fully participate in the protocol Exclusion Criteria: * Current daily use of nicotine replacement therapy or smoking cessation medications, with the exception of e-cigarettes * Current major depressive disorder based on the Patient Health Questionnaire-9 (PHQ-9) and the Beck Depression Inventory * Contraindication to progesterone treatment (e.g., current use of drugs that may inhibit CYP3A4; current or history of deep vein thrombosis, pulmonary embolus, clotting or bleeding disorder, hypertension, stroke, heart disease, or liver dysfunction or disease; or peanut allergy), * Current or within the past 3 months treatment for illicit drug use or alcohol use * Any condition or issue that, in the opinion of the clinical team, precludes participation in the trial.