ATHLETICS: Australia will have a full and strong contingent of female marathoners at the Rio Olympics after Lisa Weightman became the third runner to better the qualifying standard with a fighting second-placed finish in the Houston marathon.

Weightman led for the first 30 kilometres of the race early Monday (AEDT) before being overtaken by eventual winner Biruktayit Degefa of Ethiopia.

The Australian's time of two hours 27 minutes and 35 seconds saw her join countrywomen Jess Trengove and Milly Jane Clark in bettering the qualifying mark for Rio.

It was the 37-year-old Weightman's first marathon since giving birth to son Pete 13 months ago.

She was paced most of the way in Houston by her husband Lachlan McArthur, who clocked a PB to finish 34th in the men's race.

Weightman was 33rd in her Olympic marathon debut in Beijing eight years ago and then finished a creditable 17th in 2:27:32 at the 2012 London Games.

Trengove smashed the Rio qualifying mark with a commanding victory at the Melbourne marathon in October while Clark clocked an outstanding time of 2:29:07 on her debut over the distance to claim third spot in the 2015 Amsterdam marathon.

Australia can enter a maximum of three athletes in any individual event in Rio.

The marathon qualifying period ends on April 24.

AAP