Liggins Institute

IMPROVE trial: Improving Maternal and Progeny Risk of Obesity Via Exercise

A randomised controlled trial to reduce risks of obesity in over-weight pregnant women and their babies

The Liggins Institute is inviting pregnant women who are over-weight to take part in a clinical trial to assess the effectiveness of regular, moderate exercise in reducing health risks due to obesity for the women and their babies.


New Zealand has one of the highest rates of over-weight and obese people in the developed world. Obesity is associated with a number of serious health conditions such as diabetes and heart disease.

Babies born to mothers who are over-weight or obese have increased risks of developing these diseases as they grow up.

Regular exercise is recommended for pregnant women who do not have any medical or pregnancy related problems. There is evidence that exercise is good for the health of both mother and baby.

Previous research at the Liggins Institute has shown that moderate exercise in pregnancy by mothers of normal weight results in a small reduction in maternal weight gain and offspring birth weight with no adverse effects on the health of mother or baby. Read more

We are now investigating whether regular, supervised exercise will also have benefits for overweight, pregnant women and their babies. The results of this study will help us plan a way of reducing the risk of obesity for all communities.

The IMPROVE trial has received ethical approval from the Health and disability Ethics Committee of the Ministry of Health (Ref. 12/NTB/24). It is supported by Gravida: National Centre for Growth and Development and is being conducted at the Liggins Institute of the University of Auckland.



Principal study investigators




To take part in the IMPROVE trial, participants must be:

  • less than 20 weeks pregnant
  • between 18 and 40 years of age
  • overweight - Body mass index (BMI) above 25 (contact your lead maternity carer/midwife to check this, or contact us directly with your current weight and height)

Participants must not

  • smoke during this pregnancy
  • have any major medical illness
  • be taking any medication that affects baby’s growth


To discuss taking part in the IMPROVE trial


IMPROVE trial - study outline

There are two groups in this study, an intervention group and a control group. Participants are randomly assigned to one group or the other. The intervention group is asked to do regular exercise; the women in the control group can do their normal activities.

Intervention group

The participants in the intervention group need to exercise, as directed, for 30-40 minutes 5 times a week from 20 weeks to 36 week (5th to 8th month) of pregnancy. They are provided with an exercise cycle so they can exercise at home. It is necessary to exercise regularly at a given heart rate: participants receive a heart rate monitor to wear during exercise and will maintain exercise diaries.

Control group

The participants in the control group do not need to exercise and can do any physical exercise they wish. They will maintain an exercise diary but will not receive exercise cycles until after they have completed the study.

All participants - what else is involved?


  • All women have fetal ultrasound scans, to measure their babies' growth, every 4 weeks at Middlemore hospital.
  • Participants visit the Paykel Clinical Research Unit at the Liggins Institute in Grafton, Auckland three times:
    • Once during the 5th month and once in the 8th month of pregnancy. At this time we will take some measurements and blood tests, and carry out a fitness assessment on an exercise cycle. This takes about 1-2 hours.
    • Approximately two weeks (14 days) after delivery a DXA scan will be performed on mother and baby to measure muscle and fat content.

Participants receive petrol vouchers to cover the cost of each of these trips and free parking at the Institute.




Benefits and risks of participating in this study

We believe that regular exercise will help to improve mothers’ health, and the long-term health of their babies. Extensive research over many decades has demonstrated that daily moderate exercise is safe for pregnant women and well is tolerated. There are recognised benefits of regular physical activities during pregnancy and the major obstetric societies recommend at least 30 minutes of moderate exercise daily.

We believe exercise will help reduce baby’s birth weight a little and protect it from later obesity and obesity related problems. We think there will be benefits for mothers as well, with less weight gain during pregnancy and less risk of pregnancy related diabetes. They may also have an easier labour and delivery.

The research team communicates closely with participants’ maternity caregivers/midwives throughout the study. If there are any health concerns during the study participants may be required to stop exercising.

Evaluation of body fat content by DEXA scanning requires brief exposure to radiation. Radiation carries a small possibility of promoting neoplastic tumours. The radiation from a DEXA scan is extremely low. It is only one tenth of that of a chest X-ray and less than what you would get on a short international flight to Australia.

All participants who complete the study will receive a free exercise cycle to keep together with instructions and an exercise programme to help them develop and maintain fitness after pregnancy.

Further information

Download the participant information sheet which includes full study details, participants’ rights and contacts for further information, concerns and complaints.

Participant information sheet (127.2 kB, PDF)