In the Northern hemisphere, it's commonly said women prefer to give birth around summer. It would appear this does not hold for Australia. The graph below actually suggests most babies are conceived over the summer months (December to February) down under!
In preparing the graph above (a "seasonal subseries plot"), I could not help but notice the spike in the numbers for each month around 2005. It turns out that was real - Australia did experience a temporary increase in its fertility rate. Whether that was thanks to government policy (baby bonus, tax subsidies) or other causes is not known.
Full R code is on my git server. Check it out - there are a few more plots in there already. I might write about these later.