The randomized controlled trial (RCT) recruits pregnant women with de novo diagnosis of gestational diabetes. Women bearing a singleton pregnancy are randomized into four arms: DHA, oat, oat plus DHA, and placebo. The primary outcomes are cord blood leptin concentration in the newborns and maternal fasting glucose levels at 8 weeks post-intervention.

DHA is a long-chain fatty acid that has been shown to increase insulin sensitivity in basic science studies. Some studies have reported that oat (β-glucan) intake in patients with type 2 diabetes may improve glycaemic control. Evidence is emerging that gut microbiota may play an important role in energy homeostasis and glucose metabolism. This RCT aims to test the hypothesis that DHA and/or oat intake may improve glycemic control in women with gestational diabetes mellitus (GDM), and may impact metabolic health in fetuses/infants as indicated by cord blood leptin level. Changes in microbiota may be linked to these effects.

Growing evidence suggests that epigenetic changes may occur during fetal development in response to an adverse in utero environment, and this may "program" the risk of metabolic syndrome and type 2 diabetes in adulthood. GDM's offspring are programmed to be at substantially elevated risk of metabolic syndrome and type 2 diabetes in adulthood. We will explore whether the intervention may affect epigenetic profile in placental DNA in GDM.

Pregnant women bearing a singleton fetus without any evidence of malformation and with a de novo diagnosis of GDM at 22-28 weeks of gestation will be randomized into four arms: DHA, oat, oat plus DHA, and placebo. We will collect maternal blood and stool specimens on recruitment and 8-weeks post-intervention, cord blood and placenta specimens at delivery. The primary outcomes are cord blood leptin concentration in the baby, and fasting blood glucose at the 8 weeks post-intervention in the mother.

Inclusion Criteria:

1. Han nationality
2. 20-45 years old
3. singleton pregnancy
4. natural conception
5. the pregnant women with de novo diagnosis of gestational diabetes mellitus during 22-28 weeks of pregnancy

Exclusion Criteria:

1. Pregnant woman or the biological father has diabetes mellitus (Type I or II)
2. the woman has severe diseases or life threatening conditions such as HIV, cancer, renal failure
3. the fetus has known congenital malformation or genetic defects
4. in-vitro fertilization
5. active hepatitis
6. tuberculosis
7. syphilis
8. drug abuser
9. multiple pregnancy