It seems to be due to lack of access/income and race if I recall correctly. For the highest income quintile it’s roughly in line with the OECD. The lower your income the worse you do, and if you’re black the numbers are off the charts. A few years ago you were 3X more likely to die in childbirth in America than Canada, and 6X more likely than Scandinavia. Not sure the exact stack up now.
[edit] Here’s an NPR write up from 2017 [1] and 2023 [2]. And a more recent one suggesting the numbers may be overestimated in aggregate but suggests race is a huge factor, with black women 3X more likely to die in childbirth than white. Note the CDC disagrees with the idea it’s over-counting. [3] Even using the revised-down estimates America does not compare favorably to the OECD. [4]
[1] https://www.npr.org/2017/05/12/527806002/focus-on-infants-du...
[2] https://www.npr.org/2023/07/09/1186694708/u-s-maternal-death...
[3] https://www.npr.org/sections/health-shots/2024/03/13/1238269...
[4] https://data.worldbank.org/indicator/SH.STA.MMRT?locations=O...