What we’ve done is cause an unintended spike

[GoodTaste]

Is "cause" a verb here? The structure of "is cause" sounds peculiar and it appears to be me that for it to be easily understood, "is causing" might be better. I am not sure.

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Researchers say that in some countries, pregnant women have received less care than they need because of lockdown restrictions and disruptions to health care. As a result, complications that can lead to stillbirths were probably missed, they say.


“What we’ve done is cause an unintended spike in stillbirth while trying to protect [pregnant women] from COVID-19,” says Jane Warland, a specialist in midwifery at the University of South Australia in Adelaide.

Source: Nature Sep.15, 2020
https://www.nature.com/articles/d41586-020-02618-5

 

[GoesStation]

It's correct as written. "Cause" is a bare infinitive in that sentence. It could have been written as "to cause" with no change in meaning. The participle would be grammatical but the meaning would change; with the participle, the spike would be going on now.