Almost 17 percent of parliamentarians the world over are women, the IPU said.
Nordic countries retained their reputation as bastions of female advancement, with the regional average increasing to 40.8 percent after Sweden elected a greater number of women MPs than ever before in its September polls.
Women now hold 47.3 percent of seats in the Riksdag, the Swedish parliament , as well as the justice, EU affairs, international development, energy and enterprise ministerial portfolios in the ruling centre-right government.
Rwanda actually has the highest proportion of female parliamentarians, with
48.8 percent of seats in the lower house, the IPU said.
The group also hailed the "consistent rate of progress in the Americas over the past decade," notably Costa Rica where women made up 38.6 percent of parliamentarians.
Women make up on average 20 percent of parliamentarians across the Americas, trailing only their Nordic sisters and ahead of the rest of Europe.
However, the IPU also highlighted "missed opportunities" during 2006 in post-conflict states which are undergoing electoral and parliamentary reform.
Story continues below…
Women won only 8.4 percent of seats in the newly established lower house of the Democratic Republic of Congo, and four percent in Haiti's lower house.
This contrasts with "significant increases" in female representation over recent years in polls in Afghanistan, Burundi, Rwanda, Mozambique, South Africa and East Timor, the IPU said.