North Shore healthcare professionals and expectant mums will be targeted in a new campaign which aims to tackle the trend of giving birth before 39 to 40 weeks.

The campaign – Every Week Counts (www.everyweekcounts.com.au) - is backed by research from Royal North Shore Hospital and the University of Sydney and shines a light on a baby’s crucial growth and development in the last few weeks of pregnancy.

Professor Jonathan Morris, an obstetrics and gynaecology expert from the hospital and the university, said a recent healthcare study revealed up to 60 per cent of planned caesarean sections performed before 39 weeks gestation did not have a medical or obstetric reason.

"There is a general lack of awareness amongst both clinicians and expectant parents of the short, medium and long-term implications of being born even slightly early," he said.

"Those last few weeks of gestation might seem insignificant, but - in reality - babies are going through crucial developmental phases towards the end of a pregnancy.

"For example, at 35 weeks a baby’s brain weighs only two-thirds of what it will weigh at 40 weeks."

The research reveals babies born early are more likely to:

need help with their breathing

be admitted to a neonatal intensive care unit

have jaundice

spend longer in hospital; and

be readmitted to hospital in the first year of life.

"And in the longer term, early births are linked to an increased risk of developmental problems, such as poorer school performance," Prof Morris said.

"If a woman has a healthy pregnancy and there is no clinical need for earlier delivery, waiting until approximately 39 weeks is best for baby.

"This is in line with recommendations from the Royal Australian and New Zealand College of Obstetricians and Gynaecologists."