Increases in Pre-Term Birth Rates Observed in All Races, Higher Increases in Minority Groups

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Pre-term birth (PTB) is a leading cause of infant mortality globally and is associated with both short- and long-term morbidity and mortality. PTB rates vary significantly, with some states reporting 8% PTB and others reporting 13%. Additionally, inequities in PTB rates across various racial and ethnic groups continue to persist. Authors of a study published in JAMA Network Open evaluate patterns of PTB and any related risk and protective factors from 2011 through 2022 within different racial groups in California by insurance status. Further, associations of PTB rates with risk and protective factors within these groups were also assessed.

For this retrospective cohort study, the investigators enrolled over 5.4 million singleton live births with gestational age from 22 to 44 weeks. Birth certificates from the California Department of Public Health Vital Records provided self-identified racial and ethnic groups, which included Alaska Native, Asian, Black, Hispanic, Native Hawaiian or other Pacific islander, White, or other racial group (Asian Indian, Filipina, ≥2 races, other specified group, refused to state, or unknown). Additionally, insurance group was used as a proxy for socioeconomic status (SES) and was categorized as public (eg, Medi-Cal, California Medicaid program) or nonpublic (eg, private insurance, self-pay, Civilian Health).

PTB, which is defined as a gestational age of 22 to less than 37 weeks, was based on best obstetric estimates. Further, the investigators noted that for 2011 to 2021 birth records, they were able to link hospital discharge, emergency department, and ambulatory surgery records from the California Department of Health Care Access, but 2022 records were unavailable at the time of evaluation.

Further, the study considered social determinants of health that are known to be associated with PTB risk or protection, such as having public insurance for prenatal care or childbirth, maternal place of birth, education level, number of prenatal care visits, smoking, drug use, alcohol use, housing insecurity, and intimate partner violence. Other included factors were maternal age, body mass index prior to pregnancy, mental health conditions, and other comorbidities (eg, diabetes, hypertension, autoimmune conditions, sleep disorders, asthma).

According to the results, most of the included singleton live births were among those who identified as Hispanic (47.8%) and White (27.0%), with the remainder being Asian (14.2%), Black (4.9%), Native Hawaiian or other Pacific islander (0.4%), and American Indian or Alaska Native (0.3%). Most births were delivered from those aged 18 to 34 years (76.6%) and born in the US (63.3%). Additionally, most participants resided in urban areas (61.8%).

The investigators noted that the highest PTB rates were consistently observed among those who were Black (11.3%), American Indian or Alaska Native (10.3%), or Native Hawaiian or Other Pacific Islander (9.3%) and had public insurance. The lowest PTB rates were present in White individuals with nonpublic insurance (5.8%). Additionally, from 2011 to 2022, PTB rates decreased slightly among Black individuals with nonpublic insurance (9.1% to 8.8%); however, significant increases in PTB rates were observed in most racial groups by insurance types during this period (Hispanic individuals: 7.1% to 7.4%; American Indian or Alaska Native individuals: 6.4% to 9.5%).

Associations (relative risks [RR] ≥2) were observed between PTB rates and risk factors such as pre-existing diabetes and hypertension, previous PTB, and fewer than 3 prenatal care visits. Additionally, associations (RRs >1) were observed between PTB rates and risk factors such as age above 34 years, gestational diabetes or hypertension, mental health conditions, substance use, non-sexually transmitted infection or COVID-19 infection, and interpregnancy interval of more than 59 months. The investigators also observed that sickle cell anemia and autoimmune conditions were associated with higher risk in some groups, whereas housing insecurity increased PTB risk in all public insurance groups and multiple nonpublic insurance groups, with RRs ranging from 1.87 (95% CI, 1.64-2.14; P < .001) for Black individuals who have public insurance to 4.18 (95% CI, 3.35-5.22; P < .001) for White individuals with nonpublic insurance.

According to the authors, limitations of this study included the lack of data on the interventions used as well as limited numbers for some racial and ethnic groups (eg, Filipino, multiple races). Additionally, the authors noted that although efforts were made to avoid overadjustment bias, further analyses with adjusted factors may be helpful at clarifying aggregate risk. Further, the authors suggested that future research should expand to include a national sample, allowing for more detail analyses of these groups while exploring potential patterns in other public health systems.

REFEERENCE

Jelliffe-Pawlowski LL, Baer RJ, Oltman S, et al. Risk and Protective Factors for Preterm Birth Among Racial, Ethnic, and Socioeconomic Groups in California. JAMA Netw Open. 2024;7(9):e2435887. doi:10.1001/jamanetworkopen.2024.35887