The 20210G>A and 19911A>G polymorphisms of prothrombin gene and recurrent miscarriages

To Test or Not to Test: Routine Thrombophilia Diagnostic Screening of Women with Reproductive Failures

BACKGROUND

Recurrent reproductive failure is a global health issue affecting a significant number of women. Thrombophilias have been implicated as a possible cause. Inherited thrombophilias include a single nucleotide variant on factor V Leiden and prothrombin.

OBJECTIVE

The aim of this study was to evaluate the association between the following single nucleotide variants: factor V Leiden (c.1601G>A), the prothrombin gene (c.*97G>A) and the reproductive failure in the Polish population.

METHODS

The study was conducted in a group of 545 patients with recurrent pregnancy loss, RPL (≥2 miscarriages), and in a group of 641 patients with infertility. The distribution of genotypes for the selected variants were determined by RFLP-PCR and by the real-time PCR method.

RESULTS

A variant of the F5 gene was found in 5.14% of patients with RPL and in 6.08% of infertile women. A variant of the F2 gene was identified in 0.73% of patients with RPL and in 2.03% of women with infertility. The frequency in the study groups did not differ from that in the general population. No association between the studied variants of the F5 gene or the F2 gene and the predisposition to reproductive wastage was found.

CONCLUSIONS

Recommendations for routine thrombophilia testing in women with recurrent miscarriages should be revisited. The decision regarding testing should be made individually depending on additional factors indicating an increased risk of venous thromboembolism.

Hereditary thrombophilia and recurrent pregnancy loss: a systematic review and meta-analysis

STUDY QUESTION

Is there an association between hereditary thrombophilia in pregnant women and risk of recurrent pregnancy loss (RPL)?

SUMMARY ANSWER

Pregnant women with hereditary thrombophilia have an increased risk of RPL, especially for pregnant women with the G1691A mutation of the factor V Leiden (FVL) gene, the G20210A mutation of the prothrombin gene (PGM), and deficiency of protein S (PS).

WHAT IS KNOWN ALREADY

Prior studies have suggested that pregnant women with hereditary thrombophilia have a higher risk of RPL, however, the results are inconsistent; furthermore, a complete overview is missing. This lack of information is an obstacle to the risk assessment of RPL in pregnant women with hereditary thrombophilia. A comprehensive meta-analysis on the relation between hereditary thrombophilia and the risk of RPL is needed.

STUDY DESIGN, SIZE, DURATION

A systematic review and meta-analysis was performed using observational studies published in English before 1 April 2020 to evaluate the relation between hereditary thrombophilia and risk of RPL.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Relevant studies were identified from PubMed, Web of Science, and EMBASE searches and complemented with perusal of bibliographies of retrieved articles. The exposure of interest was hereditary thrombophilia, including FVL mutation, PGM, deficiency of antithrombin (AT), deficiency of protein C (PC), and deficiency of PS. The overall risk estimates were pooled using random effects models. Subgroup and sensitivity analyses were carried out to explore possible sources of heterogeneity and assess the robustness of the results.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 89 studies involving 30 254 individuals were included. Results showed that women with FVL mutation (odds ratio (OR): 2.44, 95% CI: 1.96-3.03), PGM (OR: 2.08, 95% CI: 1.61-2.68), or deficiency of PS (OR: 3.45, 95% CI: 1.15-10.35) had higher risks of developing RPL. Compared with the reference group, there was no observed relation between a deficiency in AT or PC and RPL (all P > 0.05). Heterogeneity in the risk estimates of RPL was partially explained by geographic region, definitions of RPL, types of RPL, and controlled confounders. Sensitivity analyses validated the robustness of the findings.

LIMITATIONS, REASONS FOR CAUTION

Only 39 of the included studies controlled for one or more confounders, and the heterogeneity across all included studies was high. Based on the data available, we cannot determine whether this association is confounded by other potential risk factors of RPL.

WIDER IMPLICATIONS OF THE FINDINGS

This systematic review and meta-analysis show a possible association between hereditary thrombophilia and an increased risk of RPL, suggesting that testing for hereditary thrombophilia should be considered in individuals with RPL.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by the Hunan Provincial Key Research and Development Program (Grant number: 2018SK2062) and National Natural Science Foundation Program (Grant number: 81973137). There are no conflicts of interest.

REGISTRATION NUMBER

N/A.

Selected genetic causes of miscarriages

Approximately 15–25% of pregnancies end in spontaneous abortion, which is an expulsion from the mother body of the fetus weighing less than 500 g or before the 20th week of gestation. Determining abortions etiology is difficult due to its multifactorial character. Chromosomal abnormalities cause 38.6–80% of miscarriages. The largest group (93%) of chromosomal aberrations found in miscarried fetuses are numerical changes – aneuploidies and polyploidies. Much rarer (7%) are unbalanced structural aberrations, which can arise de novo or can be inherited from a carrier parent. In couples with spontaneous abortions, reciprocal chromosomal translocations (RCT) occur the most frequently, next are Robertsonian translocations and inversions. More complex chromosome abnormalities, e.g. double aneuploidies are found in 3.8% of fetuses. Another group of causes responsible for abortions are monogenic diseases of embryo or fetus resulting from autosomal dominant, autosomal recessive or X-linked mutations. Among mutations which may contribute to pregnancy loss are factor V Leiden gene mutations (c.1601G>A, earlier 1691G>A) and prothrombin gene mutation (c.97G>A, earlier 20210G>A). The research on mutations in candidate genes, eg.: ALOX15, CR1, CYP1A1, CYP17, CYP2D6, FOXP3, HLA-G, IL-6, KHDC3L, NLRP7, NOS3, PLK4, SYCP3, TLR3, TNF, TP53 and VEGFA is still ongoing.