The number of women with gestational diabetes mellitus (GDM) had been increasing. Maternal GDM has a great impact on both the health of the mothers and the offspring. Antenatal lifestyle interventions, in particular dietary intervention appear to be feasible to improve maternal GDM and weight gain. To the best of our knowledge, there has been no such trial examining the feasibility of a lifestyle intervention in pregnant women in Hong Kong. Therefore, we plan to conduct a randomized controlled trial comparing a lifestyle modification program (LMP) in early pregnancy and the usual antenatal care in high risk Chinese pregnant women in Hong Kong. Intervention group subjects (n=110) will participate in a dietitian-led LMP including dietary and exercise component from the first antenatal (AN) booking to 24 weeks gestation. 110 women in the control group will receive routine hospital antenatal care. The primary endpoint will be the prevalence of GDM measured using a 75 g oral glucose tolerance test at 24-28 weeks gestation. The secondary endpoints will be the proportion of infant born with large for gestational age (>=95th percentile of the customized birth weight) and macrosomia (>=4 kg at birth). The intervention group involves dietary and exercise advice and monitoring. No drug or invasive procedure is involved. The control group will receive routine antenatal care and will be provided with an educational pamphlet on diet and exercise during pregnancy.

Inclusion Criteria:

• Chinese origin
• Reside normally in Hong Kong
• Singleton pregnancy
• Gestational age <= 12 weeks at the time of recruitment
• Could speak and understand Chinese
• Fulfill at least one of the following criteria for high risk of GDM at the time of recruitment based on the update hospital protocol implemented since 1st May 2014
• Maternal age >= 35 years old at expected date of confinement.
• Prior history of GDM or birth of child >= 4 kg
• Pre-pregnant BMI or BMI at 1st trimester >= 25 kg/m2
• Family history of diabetes at 1st degree relatives
• Willing to give informed written consent and follow the study procedures

Exclusion Criteria:

• Concurrent participation in any clinical trial or study
• With renal, liver or thyroid dysfunction, cognitive impairment, or any other indication of a major medical or psychological illness, as judged by the investigators as ineligible to participate the study
• Multiple pregnancies
• Pre-existing DM
• With physical restriction that prevents from exercising
• Substance abuse