The aim of this study is to encourage smoking cessation in women with substance use disorders by providing knowledge of expired carbon monoxide. We hypothesize that women who are provided knowledge of their expired carbon monoxide and the associated percent fetal carboxyhemoglobin will have a greater success at quitting smoking during pregnancy than women who are not provided this information.

A secondary aim of the study is to correlate expired carbon monoxide throughout pregnancy with infant birth weight.

This is a randomized controlled trial. Pregnant smokers who are substances users who meet inclusion criteria will be offered participation in the study at their first obstetrical appointment. Patients who consent to participate will be randomized.

At the enrollment/randomization visit, women will be randomized to either the intervention (knowledge of and interpretation carbon monoxide levels and associated percent fetal carboxyhemoglobin) or control group (no information on carbon monoxide and associated percent fetal carboxyhemoglobin). Allocation will be computer generated. This will be done after the patient meets all inclusion criteria. If randomization to the intervention arm, the patient will be notified of carbon monoxide and associated fetal carboxyhemoglobin levels at each obstetrical visit and counseled on how it affects maternal and fetal health.

If randomized to the control arm, the patient will have expired carbon monoxide and associated fetal carboxyhemoglobin levels measured at each obstetrical visit but blinded to these results. These patients will not be notified of the levels, nor counseled on what levels mean for maternal or fetal health.

See below for intervention and control protocols.

Maternal demographic (age, race, socioeconomic status), medical history (other medical problems, medications, height, weight) and obstetric history (parity, gestational age) data will be abstracted from the patient's chart and supplemented with a patient questionnaire at the enrollment/randomization visit. The primary outcome is the expired maternal carbon monoxide level at the last obstetric visit or at delivery. This will be determined by the Smokerlyzer device used to measure this. Secondary aims of the study will be to evaluate how maternal carbon monoxide levels correlate with fetal growth, cigarette use per day, patient satisfaction and neonatal birth weight.

All patients will have the following performed at the enrollment/randomization visit and subsequent prenatal visits:

a. The order of events for all patients will be as follows: i. Blood pressure evaluation ii. Weight iii. Fundal height iv. Patient will be asked the number of cigarettes used per day v. Patient will exhale into Smokerlyzer device to obtain expired carbon monoxide and associated percent fetal carboxyhemoglobin vi. Patients will be provided smoking cessation resources and counseling on smoking cessation in pregnancy

Intervention Protocol

1. Intervention group will undergo Smokerlyzer ® exhaled carbon monoxide measurements at enrollment, each prenatal visit, and at their last (>36 week) prenatal visit or at delivery if not captured in clinic.
2. Women will be informed of their exhaled carbon monoxide measurement at each visit as well as the correlation to fetal carboxyhemoglobin.
3. At each visit, the intervention group will receive counseling on fetal impact of smoking based on fetal carboxyhemoglobin level and institutional and state information on smoking cessation will be provided.
4. The patient will then proceed to the remainder of the obstetrical visit.

Control Protocol

1. Women in the control group will undergo Smokerlyzer ® exhaled carbon monoxide measurements at enrollment, each prenatal visit and at their final (>36 week) prenatal visit or at delivery if not captured in clinic.
2. Both levels (maternal carbon monoxide and fetal carboxyhemoglobin) will be recorded by the co-investigatory, but NOT disclosed to the patient
3. At each visit, control group will be provided institutional and state information on smoking cessation if they report continued smoking.
4. The patient will then proceed to remainder of the obstetrical visit.

For both groups:

At the time of delivery, maternal and neonatal outcome data will be recorded from the chart, including gestational age at delivery, mode of delivery, indications for delivery, birth weight, Apgar score, cord blood gas, length of stay, and neonatal complications, if any. A survey will be completed for both intervention and standard care groups after delivery.

Inclusion Criteria:

i. Age 16-45

ii. Singleton gestation

iii. Gestational age at enrollment <24 weeks

iv. Substance use disorder defined as modified National Institute on Drug Abuse ASSIST ≥4

v. Cigarette smoker using ≥10 cigarettes/day interested in quitting

Exclusion criteria:

i. Known or suspected fetal growth restriction at enrollment

ii. Known fetal anomaly, aneuploidy, or demise

iii. Not interested in smoking cessation or reduction during pregnancy

iv. E-cigarette use

Pregnant women and neonates: male and females

Over the course of the study period, which is around 10 months per participant.

As this is a low-risk study, an independent data safety monitoring board will not be formed.

We defined an adverse event as an undesirable experience or outcome occurring in a research participant, regardless of whether participation in the research study caused the event to occur. For example, placental abruption and/or stillbirth are known risks of pregnancy, and while not associated with the Smokerlyzer® device, would be considered an adverse event if it occurred during the study.

Will not discuss percent fetal carboxyhemoglobin to control group versus disclosing percent fetal carboxyhemoglobin to intervention group.