Common doctor will know very little about physiological changes during freediving, so am not sure if it makes any sense asking one. Perhaps consulting a freediving specialist, or posting the question at the
World Freediving Medical Association would be better.
If you google up the topic, you find plenty links about sleep apnea during pregnancy:
Google It is hard to tell whether it is applicable to freediving apnea too, because the physiological reactions are not completely identical in both cases.
You can also google diving and pregnancy - one of important risks is the decompression - the fetus appears to be much more sensitive for possible harm. Although DCS is of a lesser risk for common freediving (except of deep diving, or repetitive diving with short surface intervals), it may be still harmful for the fetus.
EDIT: also strong diaphragmatic contractions during apnea may possibly pose an additional risk for the fetus
Another good topic to research is pregnancy at ama divers. I found that they allegedly worked year-round and often through pregnancy. It is interesting to know, but it does not mean that the diving did not cause any harm.
