Working hypothesis and aims:

To asses Chrono Biological factors during the third trimester of gestational diabetes melittus (GDM) with birth weight and related complications. The investigators hypothesize that participants with GDM pregnancies with higher Chrono Biologocal status will be ended with higher birth weight compared to participants with GDM pregnancies with lower status. In addition, the investigators hypothesize that the Chrono Nutritional intervention program will contribute to the reduction of the rate of birth weight above percentile 90 compared with the participants with GDM in the control group.

Background: Many studies have linked pre-pregnancy obesity and the metabolic syndrome, with an increased risk of developing gestational diabetes mellitus (GDM). These factors are associate with increased risk of newborn obesity, insulin resistance and diabetes. Recently, studies have shown that the "Chrono-Biological" (CB) aspects need to be considered in this context. These factors are related to endogenous circadian clocks, which regulate many body functions depending upon cycle of light and darkness during a day of almost 24 hours. By tracks daily fluctuations in heart rate, blood pressure, hormone secretion and control of a variety of metabolic pathways. Factors that can affect the setting of the circadian clock may include; Change dark and light hours, consumptions of certain nutrients during the day and more.

Chronic rhythm disruption associated with the development of obesity, diabetes, and more. Factors such as "chrono-nutrition" (CN) have a significant impact on variations in circadian rhythms includes: meals program schedule, glucose, saturated fat, caffeine and alcohol intake, and the ratio of macronutrients. Intervention studies in adults who are obese and diabetes were able to reduce the impact of these disorders by changing the composition and schedule of meals that lead to weight loss and diabetes control. Moreover, Insomnia during pregnancy can be caused by disorders CB. Insomnia affects 30-40% of all pregnancies. Some sleep disorders can be worsening by pregnancy, particularly overweight. Currently, routine monitoring and treatment of women with GDM does not include screening for sleep disorders and CN factors.

Working hypothesis and aims: To asses CB factors during the third trimester of participants with GDM pregnancies with a weight of childbirth and related complications. The investigators hypothesize that participants with GDM pregnancies with higher CB status will be ended with higher birth weight compared to participants with GDM pregnancies with a lower status.

In addition, the investigators assume that the CN intervention program will contribute to reducing the rate of birth weight above the 90 percentile compared to control group.

Methods: In a prospective cohort study, n= 280, The investigators will review the obstetric outcomes and the impact of CB disorders and complications for mother and fetus, through questionnaires. In a clinical trial n=100, The investigators will assess the effect of CN intervention on birth weight in participants with GDM pregnancies.

Expected results: Based on the investigators preliminary research and literature, The investigators expected that due to the increasing prevalence of obesity and sleep disturbance among GDM pregnancies , and the feasibility of high interference CN factors in pregnancy, Therefore, it is important to examine the impact of CB factors on maternal and fetal.

The importance of the study: Since there is a high probability that GDM is exposed to the interference of CB factors which are not monitored during GDM, this unique study, is of great importance for understanding the potential impact of the CB factors on higher birth weight rates.

Inclusion Criteria:

• GDM first screened in 24-32 week of prenancy
• singleton pregnancy
• GDM screened in "Rabin medical center"
• signing an informed consent

Exclusion Criteria:

• women with history of metabolic disorder such as dislipidemia, heart disease, cancer, type 1 diabetes, type 2 diabetes, hypertension, kidney disease,liver disease, thyroids disorder, cancer.
• women with history of fertility drug therapy such as IVF or progsterone
• women who work night shifts
• women who work in air crew