The findings add to the existing evidence that race discrimination is a risk factor for poor health outcomes, say the researchers.
For several decades, race has been recognized as a social determinant of health and a risk factor for numerous diseases. The evidence increasingly suggests that upstream social, environmental, economic and political factors are fundamental drivers of health inequities, and that it is often racism, rather than race, that is the root cause.
For example, maternal death rates among Black and Indigenous women in the U.S. are 2-3 times higher than those of white women. Similarly, in the UK, maternal death rates are 2-4 times higher among Black and Asian women than they are among white women.
To explore the existing patterns of racial disparities in pregnancy outcomes, the researchers searched 8 electronic databases, looking for relevant studies on self-reported race discrimination and premature birth (before 37 weeks), low birthweight, and high blood pressure associated with pregnancy, and published up to January 2022.
In all, the results of 24 studies were included in the final analysis, with the number of participants in each study ranging from 39 to 9470. Most (20) studies were carried out in the US.
Study participants were of different racial and ethnic backgrounds, including Black or African American, Hispanic, non-Hispanic white, Mãori, Pacific, Asian, Aboriginal, Romani, indigenous German and Turkish.
The pooled data analysis showed that for all the outcomes studied, experience of race discrimination was associated with a heightened risks of premature birth and giving birth to a small-for-gestational age baby.
The overall odds of a premature birth were estimated to be 40% higher. When low quality studies were excluded, the odds of a premature birth were reduced but still 31% higher. And while not statistically significant, the overall odds of a small-for-gestational age baby were estimated to be 23% higher.
Similar results were obtained when further analyses of selected data were carried out.
The researchers acknowledge that many of the studies included in the pooled data analysis were of low quality, and that most were based in the U.S., and included few marginalized racial or ethnic groups other than African Americans. As such, they may not be more widely applicable to other ethnic groups and cultural settings.
Nevertheless, they point out, "Our findings align with existing evidence on perceived racial discrimination as an important risk factor for adverse pregnancy outcomes."
They explain, "Pervasive in people's day-to-day lives, racism has far reaching implications on the experiences of racialized individuals. As an upstream factor, it shapes other social determinants of health such as employment, poverty, education and housing.
"Relating more directly to health, racism can impact what services and resources are available, such as referral to specialist care, access to health insurance and access to public health services."
The researchers highlight various approaches to counter the effects of racism on health outcomes, including the need to improve the training of clinicians.
This can be done by "universally removing well-documented examples of racial bias which continue to perpetuate health inequities," they suggest.
"This includes the lack of teaching on dermatology and differential disease presentations in non-white individuals, inaccuracies in pulse oximetry technology, unsubstantiated race-based adjustments to measuring renal function, and inadequate teaching around individual biases and the social drivers of health inequities."