This study is about the application of needle-free injection device in GDM patients in order to observe the variation of blood glucose and patients' experience compared to the traditional insulin pen injection. To provide evidence for the application of needle-free syringe injection in GDM patients.

This study is a prospective, randomized, unblinded,crossover and controlled clinical trail. The first patient was enrolled on November 1, 2019. The follow-up visit of all enrolled patients in our center will be finished on June 30, 2021. There are two arms in our study : Test Group(IG,n=20) and Control Group(CG,n=20), 40 patients totally.

Test group: "Needle-free injection device, Then traditional insulin pen" Patients first received needle-free syringe for insulin injection 3~4 times per day for 2 weeks. After the period of 2 weeks, they then received conventional insulin pen for insulin injection 3~4 times per day for 2 weeks.

Control group: "Traditional insulin pen , Then Needle-free injection device" Patients first received conventional insulin pen for insulin injection 3~4 times per day for 2 weeks. After the period of 2 weeks, they then received needle-free syringe for insulin injection 3~4 times per day for 2 weeks.

Inclusion Criteria:

• Patients'diagnostic criteria of gestational diabetes mellitus(GDM) is according to the Guidelines for the prevention and control of type 2 diabetes in China (2017 Edition).
• fasting glucose or 2h post prandial glucose was abnormal after 3days' dietary control (fasting glucose ≥ 6.1 mmol/L, or 2h post prandial glucose ≥7.8 mmol/L).
• Aged≥20 years, Han, singleton pregnancy.
• Patients who gave informed consent voluntarily participated in the study, and had regular perinatal examination at our hospital and intended to deliver at our hospital.

Exclusion Criteria:

• Patients with multiple pregnancy or undergoing assisted reproductive technology.
• Patients with polycystic ovary syndrome in preconception.
• Patients with other endocrine metabolic disorders such as gestational hypertension and hyperthyroidism.
• Patients with severe anemia and hypoproteinemia, abnormal liver and kidney function, severe heart failure, respiratory failure and other systemic diseases.
• Patients on long-term medications that affect glucose metabolism.