Well, to give them credit, at least in Brazil they do seem to be doing something positive, i.e. nothing. Whether this is a deliberate decision we don't know yet.

The possibility of cases of brain injury that are not detectable with a tape measure is the most worrying development. The only reliable test for viral exposure is by using PCR, which is way too expensive, and even that could only be a preliminary screening test to show the mother had had an an infection that might have damaged the foetus, not that the foetus definitely was damaged.

The Brazilian study Joe cited describes 35 cases that the researchers investigated in detail. Of course they didn't follow up every case in the country, and their summary says:

historical birth prevalence of microcephaly in Brazil, approximately 0.5 cases per 10,000 live births, calculated from birth certificates, was lower than expected estimates of 1–2 cases per 10,000 live births (9), which might indicate general underascertainment of microcephaly in Brazil. However, during the second half of 2015 alone, >3,000 suspected cases of microcephaly (approximately 20 cases per 10,000 live births) were reported to the MoH through the special notification protocol, suggesting a sharp increase in birth prevalence.

That is, Zika seems to have increased the prevalence of microcephaly by a factor of 10 to 20 (and that's just the damage detectable with a tape measure).

Here are the World Health Organization figures:

http://www.who.int/csr/don/8-january-2016-brazil-microcephaly/en/