Lawler revealed she has been breastfeeding daughter Noa for just over five weeks.
The ad has been praised for offering a realistic and relatable view of breastfeeding and new motherhood.
The new mum has been open about wanting to normalise breastfeeding, and posted the sweet snap to celebrate World Breastfeeding Week.
The mum-of-three headed to Instagram to confront critics and defend sharing breastfeeding photos of her baby son.
The mum believes breastfeeding her daughters until four and five has helped them build strong immune systems.
The mum has now donated almost a bath full of excess breast milk to families in need.
The new mum is using her social media platform to chart her experiences of new motherhood, including breastfeeding.
The actor is being praised for normalising breastfeeding after posting a "powerful" new photo to Instagram.
“I'm experiencing a lot of things a lot earlier than expected!!! Bright orange Colostrum was another treat.”
“Well done Sainsbury’s! Finally breastfeeding friendly clothes are not classed as maternity!"