The spread of ultrasound technology in China and India, did not result in the current situation of skewed gender ratios. You're confusing the underlying cause (desire for male labor or heirs) and a healthcare tool.
How that technology was used, may have had a role in amplifying or accelerating the result (they could still just kill the baby girl after birth). Obvious, simple proof: ultrasound tech didn't cause the same extreme gender skew outcome in the US, Germany, France, UK, Russia, South Korea or Japan, those nations chose not to disproportionately kill baby girls despite having ultrasound tech (that's also the case for nearly all nations).
China and India should have widely available ultrasound tech. All nations should.