New Zealand's midwives believe the problem of childhood obesity doesn't start with pregnant mothers - the issue is created well before that stage.

As part of a childhood obesity crackdown, the Government's pushing programmes centred on weight gain during pregnancy and gestational diabetes.

But College of Midwives spokesperson Alison Eddy said ideally women should already be at a healthy weight when they fall pregnant.

"If you are obese and you become pregnant, then there's very little that you can do to reduce your obesity - its certainly not recommended to reduce your weight or take up a lot of exercise."

Alison Eddy said pregnant women and midwives are being held responsible for a range of social ills.

She said that although programmes for healthier pregnancies are useful measures, she's concerned that it adds to the expectation on the midwifery profession.

"Its yet again more expectation on us as a workforce and a profession - a women's workforce who are really struggling hard to keep up the volume of expectation on them."

Eddy said she fears the changes will put further pressure on women during what can already be a stressful time.

Minister of Health Jonathan Coleman said no single strategy will fix the obesity problem and that's why they've developed a range of interventions within the plan.

They include targeted interventions for the obese, more support for those deemed at risk of becoming obese, and broad strategies to make healthier choices easier.

Dr Coleman said from December 2017, 95 percent of children identified as obese on B4 school checks will be referred to health professionals for clinical assessment and interventions.