TAU (the control group) provides participants with information about the benefits of mindfulness in pregnancy and offers referrals for psychotherapy in the community. Participants in TAU are contacted monthly via phone or videoconference call to maintain engagement.

Change in the perceptions of daily life stress from 8 weeks to 3 months will be measured using the 10-item Perceived Stress Scale (PSS). Questions 1, 2, 3, 6, 9, and 10 on the PSS are scored 0, 1, 2, and 3. Questions 4, 5, 7, and 8 on the PSS are reverse scored 3, 2, 1, and 0. Total scores on the PSS are calculated by summing the score for each question. Total scores on the PSS range from 0-40, with higher scores indicating higher perceived stress. Scores ranging from 0-13 would be considered low stress, scores ranging from 14-26 would be considered moderate stress, and scores ranging from 27-40 would be considered high perceived stress.

Change in anxiety symptoms from baseline to 8 weeks will be measured using the 16-item Penn State Worry Questionnaire (PSWQ). Questions 2, 4-7, 9, and 12-16 on the PSWQ are scored 1-5. Questions 1, 3, 8, 10, and 11 on the PSWQ are reverse scored 5-1. Total scores on the PSWQ are calculated by summing the score for each question. Total scores on the PSWQ range from 16-80, with higher scores indicating higher worry. Scores ranging from 16-39 would be considered low worry, scores ranging from 40-59 would be considered moderate worry, and scores ranging from 60-80 would be considered high worry.

Change in anxiety symptoms from 8 weeks to 3 months will be measured using the 16-item Penn State Worry Questionnaire (PSWQ). Questions 2, 4-7, 9, and 12-16 on the PSWQ are scored 1-5. Questions 1, 3, 8, 10, and 11 on the PSWQ are reverse scored 5-1. Total scores on the PSWQ are calculated by summing the score for each question. Total scores on the PSWQ range from 16-80, with higher scores indicating higher worry. Scores ranging from 16-39 would be considered low worry, scores ranging from 40-59 would be considered moderate worry, and scores ranging from 60-80 would be considered high worry.

Change in rumination from baseline to 8 weeks will be measured using the 10-item Ruminative Response Scale (RRS-10). Questions 1-10 on the RRS-10 are scored 1-4. Total scores on the RRS-10 are calculated by summing the score for each question. Total scores on the RRS-10 range from 1-40, with higher scores indicating higher rumination.

Change in rumination from 8 weeks to 3 months will be measured using the 10-item Ruminative Response Scale (RRS-10). Questions 1-10 on the RRS-10 are scored 1-4. Total scores on the RRS-10 are calculated by summing the score for each question. Total scores on the RRS-10 range from 1-40, with higher scores indicating higher rumination.

Change in mindfulness from baseline to 8 weeks will be measured using the 39-item Five Facet Mindfulness Questionnaire (FFMQ). The FFMQ consists of five subscales, which are calculated by summing the following questions, which are scored 1-5 (questions followed by "R" are reverse scored 5-1): observing = questions 1, 6, 11, 15, 20, 26, 31, and 36; describing = 2, 7, 12R, 16R, 22R, 27, 32, and 37; acting with awareness = 5R, 8R, 13R, 18R, 23R, 28R, 34R, and 38R; nonjudging of inner experience = 3R, 10R, 14R, 17R, 25R, 30R, 35R, and 39R; nonreactivity to inner experience = 4, 9, 19, 21, 24, 29, and 33. For the FFMQ subscales, scores can range from 8 to 40, except for non-reactivity to inner experience, which can range from 7 to 35. For the FFMQ subscales, higher scores represent higher subscale levels of mindfulness. Total scores are calculated by summing the subscale scores and range from 39-195, with higher scores indicating higher overall levels of mindfulness.

Change in mindfulness from 8 weeks to 3 months will be measured using the 39-item Five Facet Mindfulness Questionnaire (FFMQ). The FFMQ consists of five subscales, which are calculated by summing the following questions, which are scored 1-5 (questions followed by "R" are reverse scored 5-1): observing = questions 1, 6, 11, 15, 20, 26, 31, and 36; describing = 2, 7, 12R, 16R, 22R, 27, 32, and 37; acting with awareness = 5R, 8R, 13R, 18R, 23R, 28R, 34R, and 38R; nonjudging of inner experience = 3R, 10R, 14R, 17R, 25R, 30R, 35R, and 39R; nonreactivity to inner experience = 4, 9, 19, 21, 24, 29, and 33. For the FFMQ subscales, scores can range from 8 to 40, except for non-reactivity to inner experience, which can range from 7 to 35. For the FFMQ subscales, higher scores represent higher subscale levels of mindfulness. Total scores are calculated by summing the subscale scores and range from 39-195, with higher scores indicating higher overall levels of mindfulness.

Change in rates of psychiatric diagnoses from baseline to 3 months will be measured using the Structured Clinical Interview for DSM-5 (SCID-5). The SCID-5 consists of a semistructured interview administered to participants by a clinician or trained mental health professional to determine participants' current and previous psychiatric diagnoses.

Change in disinhibition from 8 weeks to 3 months will be assessed by the Go/No-Go task (GNG). The GNG task is administered on the computer and asks participants to respond to visual stimuli that is presented continuously. Participants must make a motor response for the "go" stimulus and withhold a motor response for the "no-go" stimulus. The proportion of no-go targets in which an individual successfully withholds a motor response will provide a measure of response inhibition, with fewer errors indicating better response inhibition and a higher error rate indicating a greater tendency towards disinhibited behavior.

Change in attention from baseline to 8 weeks will be assessed by the Stroop Color-Word Test. The Stroop Color-Word Test is a computerized task in which participants are required to name the color of a written color word while inhibiting the impulse to read the word itself. The difference between mean response times of correct responses on incongruent and control trials is used to compute an interference score, which provides a measure of attention, with lower scores indicating greater attentional deficits.

Change in attention from 8 weeks to 3 months will be assessed by the Stroop Color-Word Test. The Stroop Color-Word Test is a computerized task in which participants are required to name the color of a written color word while inhibiting the impulse to read the word itself. The difference between mean response times of correct responses on incongruent and control trials is used to compute an interference score, which provides a measure of attention, with lower scores indicating greater attentional deficits.

Change in cognitive inflexibility from baseline to 8 weeks will be assessed by the Wisconsin Card Sorting Task (WCST). The WCST is a computerized task in which participants have to match a target card with one of four category cards under changing conditions. The number of incorrect responses that would have been correct for the preceding condition provides a measure of cognitive inflexibility, with higher scores indicating greater cognitive inflexibility.

Change in cognitive inflexibility from 8 weeks to 3 months will be assessed by the Wisconsin Card Sorting Task (WCST). The WCST is a computerized task in which participants have to match a target card with one of four category cards under changing conditions. The number of incorrect responses that would have been correct for the preceding condition provides a measure of cognitive inflexibility, with higher scores indicating greater cognitive inflexibility.

Change in emotion regulation from baseline to 8 weeks will be measured using the 10-item Emotion Regulation Questionnaire (ERQ). The ERQ consists of two subscales, which are calculated by summing the following questions, which are scored 1-7 (none reverse scored): cognitive reappraisal = questions 1, 3, 5, 7, 8, and 10; expressive suppression = questions 2, 4, 6, and 9. For the ERQ subscales, scores can range from 1-42, with higher scores indicating higher use of that particular emotion regulation strategy and lower scores indicating less frequent use.

Change in emotion regulation from 8 weeks to 3 months will be measured using the 10-item Emotion Regulation Questionnaire (ERQ). The ERQ consists of two subscales, which are calculated by summing the following questions, which are scored 1-7 (none reverse scored): cognitive reappraisal = questions 1, 3, 5, 7, 8, and 10; expressive suppression = questions 2, 4, 6, and 9. For the ERQ subscales, scores can range from 1-42, with higher scores indicating higher use of that particular emotion regulation strategy and lower scores indicating less frequent use.

Participant satisfaction will be measured qualitatively with brief qualitative interviews performed at the end of the intervention, during which participants will have the opportunity to comment on their experiences in the group in an open-ended format. Responses during the interview will be recorded and evaluated using a thematic analysis.

Engagement will be measured by session attendance rates. Attending 4 of the 8 group sessions is will be considered completion of the intervention and, thus, sufficient engagement.

Engagement will be assessed by the completion of daily homework as indicated by homework logs. Participants will be asked to practice mindfulness three days per week during the intervention period and will record the duration and type of meditation completed each day. Space will also be provided for participants to make note of anything they noticed about their practice. More frequent practice of mindfulness per week indicates higher levels of engagement.