One in five mothers are not being checked for perinatal mental health — and the women at highest risk are the most likely to miss out, researchers have found.

The first Australian study to review mental health screening in a large national sample of pregnant women over time has found that coverage rose from 21% in 2000 to 79% in 2017.

However, the self-reported data, from 7500 mothers participating in the Australian Longitudinal Study on Women’s Health, suggested many were falling through the net.

Mothers with prior emotional distress were 23% less likely than others to receive both antenatal and postnatal screening in accordance with health department guidelines, and older mothers were 35% less likely to be checked twice.