The study plans to recruit patients with recurrent miscarriage and detect their niacin, thiamine, vitamin A, vitamin B6, vitamin B12, vitamin D levels in plasma, evaluating if some lack exists.

Dr. Shi Hongjun from West Lake University has confirmed in a mouse model that a decrease in maternal niacin levels caused by a low niacin diet can lead to stillbirth(HJ Shi, et al. 2017). Due to the lack of a recognized clinical niacin test, it is unclear whether niacin deficiency is associated with abortion. However, some studies have showed: 1. Nearly one-third of pregnant women present low niacin level during the first trimester of pregnancy; 2. Insufficient parent niacin intake is positively correlated with the incidence of congenital heart disease; 3. Vitamin B6 affects niacin metabolism, while maternal B6 deficiency is significantly associated with early abortion. Based on this, the investigators predict that (1) a certain proportion of recurrent abortion women's niacin levels are lower than the normal range of women's normal; (2) supplementation of niacin can reduce the risk of repeated abortion.

There are many methods for detecting niacin, but so far with no reports for large population. Dr. Shi Hongjun from West Lake University used the most sensitive QTRAP 6500+ liquid chromatography tandem mass spectrometer to accurately quantify the concentration of NAD, nicotinamide, niacin and other niacin metabolites in plasma and have optimized the detection process, which would be applicated in this study.

At the same time, studies have shown that pregnant women generally have multiple vitamin deficiency during pregnancy, including plasma thiamine, vitamin A, vitamin B6, vitamin B12 and vitamin D. Therefore, in addition to detecting plasma niacin, this study will also examine the plasma levels of the remaining multivitamins to further explore the impact of nutritional deficiencies on the probability of recurrent miscarriage.

Inclusion Criteria:

• Research group 1: Recurrent abortion group: women of childbearing age who have spontaneous abortion within 20 weeks of pregnancy for 2 or more consecutive times.

Control group: 1) Women of childbearing age who had a normal pregnancy history and are not in pregnancy status now. 2) Women of childbearing age in general examination.

Exclusion Criteria:

• patients with confirmed causes unrelated to nutritional deficiencies, including

  1. Both husband and wife have been diagnosed with chromosomal abnormalities or fetal chorionic chromosomal abnormalities;
  2. The patient has been diagnosed with uterine abnormalities;
  3. vaginal bacterial infection or chlamydial infection;
  4. antiphospholipid antibody syndrome;
  5. Other immune system diseases (hypothyroidism, PCOS, hyperprolactinemia);
  6. ovarian function decline (FSH>10mIU/ml);
  7. Cervical insufficiency5.3 Exit criteria:

After being selected, the researcher was withdrawn due to various considerations.

Recurrent abortion population without confirmed diagnosis of known causes

The results of outcomes may be presented after the study has been finished.