[moved from https://discourse.openehr.org/t/representation-of-genetic-positions, originally the first response to this subtopic]
Pregnancy is different [from the example of genetic positions] since this is actually about imprecision. The accuracy support in quantity might (should) work for that - see https://specifications.openehr.org/releases/UML/latest/#Architecture___18_1_83e026d_1433773264460_352968_7042
It is certainly what it is/was intended for a
You could have
magnitude = “PW34”
accuracy = “+ - 7 days”
or theoretically have an Interval of Duration “-P7D… +P7D” - I think!!? But 'm not sure that is going to be helpful for safe.