Excess weight gain in pregnancy is a major problem affecting 55-75% of Canadian women who enter pregnancy overweight or obese and about 40% of women who are normal weight. Excess weight gain puts mothers at risk for health problems such as diabetes and developing or sustaining obesity after pregnancy, and puts their babies at risk of being born too large or developing related health problems. Mothers will be randomized to a structured high dairy protein diet and walking program or the usual care by their care provider. The investigators research questions are: Will a structured nutrition and exercise program in pregnancy compared to usual prenatal care increase the chance that mothers will achieve pregnancy weight gain within the current recommendations; improve health measures, in mother and infant at six months post-partum; to evaluate the benefits of a high dairy intake in pregnancy on maintenance of bone status in the mother and bone health outcomes in the child in early life (6 months); and to investigate the interactions between genes associated with bone health and high dairy diet supplementation on bone status in mothers during pregnancy, and bone health in mothers post-delivery and children to 6 months of age. Mothers' weight, physical activity and adherence to the nutrition plan will be assessed until birth and at follow-up with their infants at 6 months after birth. The research team will ensure new information is quickly transferred to programs to assist women to have healthier pregnancies.

This will be a 2-arm randomized 3-site trial. Recruitment will be within the community care clinics by poster and flyer advertisements. Pregnant women will be stratified by BMI categories and study site and randomized within strata to Group A (Nutrition+Exercise intervention program) or Group B (Usual Prenatal Care + Health Canada materials about healthy pregnancy + two focus group sessions exploring women's experiences with exercise, nutrition and weight gain in pregnancy).

Primary research question: Among pregnant women, does introducing a structured and monitored nutrition and exercise program (treatment) in early pregnancy compared with Usual Prenatal Care (control) increase the likelihood of attaining gestational weight gain within the Institute of Medicine (IOM) guidelines over the pregnancy period? Secondary research questions: Among pregnant women (population), does introducing a structured and monitored nutrition and exercise program in early pregnancy (intervention) compared with Standard Prenatal Care (control) lead to 1) better maternal outcomes (outcome) at 6 months post- partum; and ii) better infant outcomes (outcome) at 6 months post partum?; and 2) i) to evaluate the benefits of a high dairy intake in pregnancy on maintenance of bone status in the mother and bone health outcomes in the child in early life (6 months); and ii) to investigate the interactions between genes associated with bone health and high dairy diet supplementation on bone status in mothers during pregnancy, and bone health in mothers post-delivery and children to 6 months of age.

Experimental and Control groups: Both groups of mothers and their health care providers will be given the Health Canada materials on "Healthy Weight Gain during Pregnancy", "Eating Well with Canada's Food Guide" and the "Pregnancy Weight Gain Calculator". Baseline information will be recorded for eligible and consenting women after which they will be randomized to Experimental or Control group. Nutrition intake, physical measures and physical activity will be recorded at baseline, 26-28 weeks, 36-38 weeks of gestation, and 6 months postpartum in the same manner for both groups. All mothers will receive the study promotional materials and small incentives. Also, all mothers will be followed by their primary care provider and have usual access to public health.

Inclusion Criteria:

• Healthy pregnant females > 18 years of age with singleton pregnancies (either nulliparous or multiparous);
• less than 17 weeks gestation;
• a pre pregnancy BMI < 40 kg/m2 (owing to the fact that severe obesity with BMI> 40 may have limitations with respect to physical activity);
• plans to deliver at a Hamilton or London regional hospital or by home birth and willing to attend research visits at the community site where they were recruited;
• able to tolerate dairy foods;
• approval of primary care provider;
• able to provide signed informed consent.

Exclusion Criteria:

• unable to understand some English;
• type 1 or type 2 diabetes;
• known contraindications to exercise as recommended by the Canadian clinical practice guidelines for pregnancy;
• severe gastrointestinal diseases or conditions;
• any significant heart, kidney, liver or pancreatic diseases;
• pre-existing diabetes;
• currently smoking;
• a depression score 12 or above on the validated Edinburgh depression questionnaire.