Growth hormone (GH) has been used in the field of assisted reproduction technology for over 30 years. Studies for GH have been exploring in the applicable population, drug dosage, starting time and time limitation. In previous clinical applications, it worked as an adjuvant drug for improving ovarian reactivity. With the development of basic research and clinical applications, the improvement effect on egg quality is gradually recognized. However, which protocol of GH may work well and maximize the clinical effect remains mystery. The investigators' previous self-controlled retrospective research about 380 cases treated with GH found that the average daily injection of GH dose of 2IU for about 6 weeks can significantly improve embryo quality and clinical pregnancy outcomes of the patients with low ovarian response. The new POSEIDON standard clearly groups people with low prognosis and better classifies heterogeneous people, which may help classifying the specific subgroup that benefit most from GH of poor ovarian response (POR). The investigators design a prospective cohort study to explore whether GH low-dose long-term pretreatment can improve the outcome of assisted pregnancy and its possible mechanism in people with low ovarian reserve.

Inclusion Criteria:

1. low ovarian reserve(AMH <1.2ng/ml, or AFC <5);
2. patients who have not participated in any clinical trials within the three months;
3. patients who voluntarily signed informed consent.

Exclusion Criteria:

1. patients with BMI ≥30kg/m2;
2. patients with medical diseases such as endocrine and metabolic diseases, autoimmune disease, etc;
3. ovarian neoplasm that ≥4 cm in diameter and has no clear pathological diagnosis by surgery;
4. complicated with adenomyosis, endometriosis confirmed by surgery;
5. patients with untreated abnormal intrauterine environment, such as uterine effusion, endometritis, etc;
6. untreated hydrosalpinx.

The patients enroll for study are based on POSEIDON criteria[1], and with informed consent.