The National Archives of Scotland has the Rhynie Kirk Session Records, available to view in Edinburgh or by Intranet at many local archive centres in Scotland, or later this year (I think) via Scotlandspeople.
Kirk Session records are great for identifying the parents of illegitimate children - there is usually a much fuller narrative than is present on the baptismal register. If Elizabeth Cow was "compeared" by the Session it is difficult to predict how long before or after the birth of her child this happened, but she would be put under considerable pressure to name the father.