so please take a deep breath, kiss your children, and RELAX.
You are absolutely correct that the increased blood volumes during pregnancy
could cause an elevation in the pressure suggested by the echo. But even more importantly, ECHO is NOTORIOUSLY unreliable for evaluating pulmonary hypertension. It is wrong ALL the time. Moreover, the number 42 is barely abnormal anyways (and again, if accurate, this was during pregnancy).
What is most important is your symptoms.