Group prenatal care, and most often the CenteringPregnancy model, has been evaluated in studies using experimental or quasi-experimental designs. The research discussed here meets our standards of evidence for being methodologically strong and allowing for causal inference, unless otherwise noted. Propensity score matching studies of GPNC did not meet our standards of evidence in this review because participants were not randomly assigned to receive either group or individual prenatal care, rather the pregnant women chose to participate in group prenatal care. The studies could not fully account for the factors that lead to women preferring group prenatal care over a traditional model of care, and thus, the studies cannot provide evidence of a causal link between GPNC and perinatal outcomes.
Each strong causal study reviewed has been assigned a letter, and a complete list of causal studies can be found at the end of this review, along with more details about our standards of evidence and review method. The findings from each strong causal study reviewed align with one of our eight policy goals from Table 1. The Evidence of Effectiveness table displays the findings associated with participation in group prenatal care (beneficial, null,ii or detrimental) for each of the strong studies (A through I) in the causal studies reference list. For each indicator, a study is categorized based on findings for the overall study population; subgroup findings are discussed in the narrative. The Evidence of Effectiveness table also includes our conclusions about the overall impact on each studied policy goal. The assessment of the overall impact for each studied policy goal weighs the timing of publication and relative strength of each study, as well as the size and direction of all measured indicators.
Of the ten strong causal studies included in this review, threeiii examined how outcomes differed by race or ethnicity (beyond simply presenting summary statistics or controlling for race/ethnicity). Where available, this review presents the analyses’ causal findings for subgroups by race. A rigorous evaluation of a policy’s effectiveness should consider whether the policy has equitable impacts and should assess the extent to which a policy reduces or exacerbates pre-existing disparities in economic and social wellbeing.
Table 2: Evidence of Effectiveness for Group Prenatal Care
|Policy Goal||Indicator||Beneficial Impacts||Null Impacts||Detrimental Impacts||Overall Impact on Goal|
|Access to Needed Services||Adequate Prenatal Care||C, F, H||Positive|
|Healthy and Equitable Births||Preterm Birth||C||E, F, H||Mostly Null|
|Low Birthweight||B, C, E, F, H|
|NICU Admissions||C, E, F, H|
|Parental Health and Emotional Wellbeing||Gestational Weight Gain||I||F||Mixed|
|Rapid Repeat Pregnancy||G||E|
|Sexually Transmitted Infections (STI) Risk||G||E, G|
|Depressive Symptoms||A, D||F|
|Optimal Child Health and Development||Breastfeeding Initiation||C||E, F||Mixed|
Notes: If a study is placed in multiple impact categories (beneficial, null, detrimental) for an indicator, results were inconsistent within the study (e.g., various ways of measuring similar indicators).
Access to Needed Services
The findings from three randomized controlled trials (RCTs) show that participation in GPNC improves the likelihood that pregnant women receive adequate prenatal care.C,F,H Adequacy of prenatal care is often determined using the Kotelchuck Index, which measures adequate prenatal care on two dimensions: the month of pregnancy during which care was initiated (earlier is better) and the percentage of recommended visits received (higher is better).12
Among a large sample of mostly Black women between ages 14 to 25 with low-risk pregnancies, women in GPNC were approximately 6.4 percentage points less likely to receive inadequate care (26.6%) compared to women in individual prenatal care (33.0%).C A smaller RCT in two military settings found that women in GPNC were 6 times more likely to have adequate prenatal care, as compared to those in individual care.F Similarly, among a sample of Black women with high-risk pregnancies, women who were randomly assigned to GPNC attended an average of approximately two additional prenatal visits, as compared to women in individual care.H
Healthy and Equitable Births
The impact of participation in GPNC on birth outcomes has been widely studied,iv but findings are mostly null. The authors in the included strong causal studies hypothesized both equivalent and better birth outcomes among women participating in group prenatal care compared to individual prenatal care. The overall findings suggest that group prenatal care may work as well as individual care, but may not yield more beneficial outcomes. This evidence review classifies outcomes as null if no statistically significant differences were found between the treatment group (GPNC) and control group.
In a large two-site RCT of an enhanced CenteringPregnancy model with mostly Black young women (ages 14 to 25), 9.8 percent of mothers in group care delivered preterm, compared to 13.8 percent of mothers in individual care. This difference is equal to a beneficial risk reduction of 33 percent.C In contrast, a large 14-site RCT of the same enhanced model of CenteringPregnancy with women ages 14 to 21 found no differences in the rates of preterm birth (10.1%) between mothers in GPNC and mothers in individual care.v The GPNC sample was diverse and consisted of 56.0 percent Hispanic, 33.0 percent Black, and 10.6 percent White or other (non-Hispanic) women.E
Two smaller RCTs also found null impacts on the rate of preterm birth between women participating in GPNC and the control group.F,H The military study evaluated CenteringPregnancy,F whereas the high-risk study evaluated an unspecified model of GPNC.H Both studies conducted power analyses that indicated sufficient sample sizes to detect significant differences between groups; however, the low prevalence of preterm births in both studies, and particularly in the military study (only 10 preterm births in GPNC and only 7 in individual prenatal care),F suggests that the studies may have been statistically underpowered to detect differences in preterm birth outcomes specifically.
RCTs with varied demographic characteristics and sizes found null effects of GPNC (CenteringPregnancy, enhanced CenteringPregnancy, and unspecified models of GPNC) on low birthweight (LBW) births.B,C,E,F,H The smaller RCTsF,H may have been statistically underpowered to detect significant differences in rates of low birthweight. For example, a small RCT of Black women found a rate of low birthweight among GPNC participants that was approximately half the rate of that among individual care participants. However, the null impact was likely because the sample size was too small to detect a statistically significant difference.B
Neonatal Intensive Care Unit Admissions
The studies that have examined the impact of GPNC on the likelihood that newborns were admitted to the neonatal intensive care unit (NICU) have found no differences in admission rates between the treatment and control groups.C,E,F,H The RCTs ranged in sample size, and similar to the LBW outcome, the smaller RCTs may have been statistically underpowered to detect differences on this indicator given the low prevalence of NICU admissions.
Parental Health and Emotional Wellbeing
Several studies have examined the impact of GPNC on indicators of parental health and emotional wellbeing. RCTs of GPNC programs suggest mixed impacts overall, with positive impacts on gestational weight gain, reproductive health, and depression, discussed below.
Gestational Weight Gain
Mothers’ physical health during pregnancy has important implications for pregnancy and perinatal outcomes; both excessive weight gain during pregnancy and obesity are risk factors for pregnancy complications.I The social support associated with the GPNC model, along with discussing health-related topics and conducting self-assessments of weight and blood pressure, have been theoretically linked to a reduced likelihood of excessive weight gain during pregnancy.F,I
Secondary analysis of data from the 14-site RCT of an enhanced model of CenteringPregnancy showed that adolescent women in GPNC gained significantly less weight during pregnancy and retained less weight at 12 months postpartum compared to adolescents in the control group.I However, a small RCT conducted across two military settings found no difference in gestational weight gain between women in GPNC and individual care.F
Two studies using an enhanced model of CenteringPregnancy examined the effects of group prenatal care on the prevention and incidence of sexually transmitted infections (STIs) during pregnancy and the postpartum period.E,G The enhanced CenteringPregnancy model is bundled with HIV prevention components, such as communication skills about safe sexual behavior.E Adolescents and young adults are at a higher risk of STIs compared to older adults.14 The heightened risk is because of biological and cultural factors, such as being more likely to have sex without contraception or barrier protection.14,25 The US Centers for Disease Control and Prevention recommend that all pregnant people are screened for STIs given the effects of untreated infections during the interconception period.14,25
The two RCTs evaluating the enhanced model of CenteringPregnancy found mixed results on outcomes related to sexual risk. Neither RCT found statistically significant differences in the incidence of STIs in the intent-to-treat results.E,G However, the two-site RCT of pregnant women ages 14 to 25 found that participation in the enhanced CenteringPregnancy model led to statistically significant reductions in unprotected sexual activity at 12 months postpartum.G
The two RCTs of the enhanced model of CenteringPregnancy also found mixed results on outcomes related to rapid repeat pregnancy. The indicator is particularly relevant for adolescents included in the study populations (ages 14 to 25 and ages 14 to 21). Adolescent repeat pregnancy within 12 months of the previous live birth has been associated with an increase in mental health complications among mothers, including anxiety and stress.16,17 Research has found that adolescent women are more likely to experience inadequate prenatal care, premature birth, and low birthweight in subsequent pregnancies that occur before the age of 20, compared to older women who have multiple births.18,19
The two-site RCT of women ages 14 to 25 found that pregnant women who participated in the enhanced CenteringPregnancy model were 6.3 percentage points less likely to report a rapid repeat pregnancy at the 6-month follow up, compared to women in individual care. Rapid repeat pregnancy is defined as becoming pregnant within 12 months of the previous live birth. At the 12-month follow up, rapid repeat pregnancy was not statistically significant.G The 14-site RCT of pregnant women ages 14 to 21 receiving the enhanced model of CenteringPregnancy did not find statistically significant findings in rapid repeat pregnancy using the intent-to-treat results.E More causal evidence is needed on the potential for GPNC to reduce the occurrence of both STIs and rapid repeat pregnancies for all participants.
Maternal Depressive Symptoms and Stress
Perinatal depression is associated with negative birth, neonatal, and infant outcomes. Group prenatal care provides pregnant people with social support and facilitates discussions on topics including mental health, communication, and self-esteem.A Theoretically, GPNC may improve mothers’ emotional wellbeing, but findings from causal research are mixed.
Secondary analysis of data from the 14-site RCT of an enhanced model of CenteringPregnancy demonstrated a positive impact on perinatal depressive symptoms; the rate of probable depression decreased by 31 percent between the second trimester and the 12-month postpartum interview among women in GPNC, compared to a 15 percent reduction among women in individual care.A
A subgroup analysis of high-stressvi women participating in GPNC reported a decrease in stress from baseline to the third trimester compared to the control group. The differences between participants in group and individual prenatal care were no longer significant one year postpartum.D High-stress women in GPNC also reported a decrease in depressive symptoms from study entry to 12 months postpartum.vii,D Women who scored as low or moderately stressed at the beginning of their pregnancies did not have statistically significant differences in either stress or depressive symptoms 12 months postpartum, suggesting that GPNC was more beneficial to participants who had higher levels of stress.D
In contrast, the two-site military study found no significant differences in either stress or depression between women participating in GPNC and individual prenatal care.F The mixed findings may be because of the samples examined; the two-site military study included mostly White women with an average age of 25,F compared to mostly Black women ages 14 to 25.A,D
Optimal Child Health and Development
The causal evidence base on the impact of group prenatal care on optimal child health and development is limited to research on the likelihood that mothers initiate breastfeeding, with mixed results. The two-site RCT of an enhanced model of CenteringPregnancy with a young, largely Black sample found that women in GPNC were almost 12 percentage points more likely to initiate breastfeeding than women who received individual care.C In contrast to the positive findings, two studies found no significant differences in breastfeeding initiation, though rates of initiation were high among all women in both studies.E,F
- An impact is considered statistically significant if p<0.05. Results with p-values above this threshold are considered null or nonsignificant.
- Studies C, D, and G include subgroup analyses based on race and/or ethnicity.
- Numerous studies did not meet our standards for causal evidence as a result of using nonrandomized designs. Therefore, they are not reflected in the results of causal studies reviewed. Some of the findings are outlined in the What Do We Know, What Do We Not Know? section.
- Results are from an intent-to-treat (ITT) analysis. ITT examines the results of a randomized experiment based on original assignment to treatment and control groups, regardless of who ended up receiving the intervention and who may have switched groups. This is considered the more conservative method of determining an intervention’s effect.38
- The Perceived Stress Scale (PSS) was used to calculate stress levels and the degree to which respondents perceived situations in their lives to be unpredictable, uncontrollable and overloaded during the past month. Women were categorized as high-stress if their scores were on the top third of the PSS scale.D
- The affect-only component of the Center for Epidemiologic Studies Depression Scale (CES-D) was used to assess depressive symptoms.D