The Greek capital of Athens was hit by a series of tremors, with the strongest measuring magnitude 5.1, causing people to flee onto the streets from houses, offices and shopping malls.
In the city centre, the marble cupola cross of a historic 19th century church came loose and shattered onto the street below.
The culture ministry said the pregnant tourist was visiting the National Archaeological Museum and was struck by another visitor rushing for the exit.
The Civil Protection Authority said there was no immediate word on injuries or damage.
The Athens Institute of Geodynamics gave the natural disaster that struck at 2:13 p.m. local time (1113 GMT) a preliminary magnitude of 5.1.
"It was more like an explosion", another woman told state TV ERT on central Syntagma Square.
Emergency services said they had received calls from people who were trapped in escalators.
The quake struck about 13.7 miles north of Athens.
Two people were lightly injured from falling materials, officials said late Friday evening.
Anxious residents and office staff have crowded outdoor areas but the government denied it had ordered an evacuation alert. "The capital's buildings are built to withstand a much stronger quake", he said. Geological Survey gave it a preliminary magnitude of 5.3. "But we need more time and data to have a clear picture".
News media reported electricity outages but said internet connections were still operating.
Greece, one of the most earthquake-prone countries in Europe, is situated at a convergence point where three massive plates of the Earth's crust - Eurasian, Arabic and African - grind together.
In July 2017, a 6.7-magnitude quake rocked the Kos, killing two people, injuring scores and causing extensive damage to the island's historic buildings.