Settled science: Actual exposure to hot temperatures while pregnant *doesn't* cause birth defects, but being pregnant when it's warm outside at night *does* cause birth defects?

Extreme heat contributes to rare childhood blindness — The Daily Climate

Researchers found that a five-degree increase in the daily minimum apparent temperature – a formula derived using temperature, vapor pressure and wind speed – increased the likelihood of developing cataracts by 51 percent.
...Indeed, heat exposure during pregnancy hasn't previously been linked to birth defects: Earlier studies looking at hot tub and sauna use, as well as cooking in a hot kitchen, lack of air conditioning or even exposure to temperatures above 100º Fahrenheit while pregnant have failed to find links to congenital defects.