The measure can be very different elsewhere. The WHO defines a maternal death as "the death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of the duration and the site of the pregnancy, from any cause related to or aggravated by the pregnancy or its management, but not from accidental or incidental causes."
you'll notice in this study that 30.0% of deaths occurred 43–365 days postpartum, so you will have to adjust numbers accordingly if you are comparing the USA to what most other countries measure. (and not all use the WHO definition!) The reason they use the 42 day cutoff is I assume to aid with other-country comparison. Still lots of websites that compare maternal mortality across the world get this wrong, and compare USA deaths for a full year vs other country deaths for 30-60 days postpartum.