Anticoagulant Therapy in Pregnant Women with Mechanical Heart Valves: Italian Federation of Centers for Diagnosis and Surveillance of the Antithrombotic Therapies (FCSA) Position Paper

The management of anticoagulant therapy in pregnant women with mechanical heart valves (MHVs) is difficult and often challenging even for clinicians experienced in the field. These pregnancies, indeed, are burdened with higher rates of complications for both the mother and the fetus, compared to those in women without MHVs. The maternal need for an optimal anticoagulation as provided by vitamin K antagonists is counterbalanced by their teratogen effect on the embryo and fetus. On the other hand, several concerns have been raised about the efficacy of heparins in pregnant women with MHVs, considering the high risk of thrombotic complications in these patients. Therefore, numerous clinical issues about the management of pregnant women with MHVs remain unanswered, such as the selection of the best anticoagulant agent, the optimal anticoagulation levels to be achieved and maintained, and the evaluation of long-term effects for both the mother and the fetus. Based on a comprehensive review of the current literature, the Italian Federation of the Centers for the Diagnosis and the Surveillance of the Antithrombotic Therapies (FCSA) proposes experience-based suggestions and expert opinions. Particularly, this consensus document aims at providing practical guidance for clinicians dealing with pregnant women with MHVs, to optimize maternal and fetal outcomes while guaranteeing adequate anticoagulation. Finally, FCSA highlights the need for the creation of multidisciplinary teams experienced in the management of pregnant women with MHVs during pregnancy, delivery, and postpartum, in order to better deal with such complex clinical issues and provide a comprehensive counseling to these patients.

Mechanical Heart Valves, Pregnancy, and Bleeding: A Systematic Review and Meta-Analysis

Anticoagulant therapy is essential in pregnant women with mechanical heart valves to prevent valve thrombosis. The risk of bleeding complications in these patients has not gained much attention. This systematic review and meta-analysis investigate the prevalence of bleeding peri-partum and post-partum in women with mechanical heart valves and also investigate whether bleeding risk differed across anticoagulant regimens or according to delivery mode. The present study was conducted according to The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement. Studies reporting bleeding prevalence in pregnant women with mechanical heart valves receiving anticoagulant therapy were identified through PubMed and Embase on December 08, 2021. Data on bleeding complications, delivery mode, and anticoagulation therapy were extracted. A total of 37 studies were included, reporting 423 bleeding complications in 2,508 pregnancies. A meta-analysis calculated a pooled prevalence of 0.13 (95% confidence interval [CI]: 0.09-0.18) bleeding episodes per pregnancy across anticoagulant regimens. The combination of unfractionated heparin (UFH) and vitamin K antagonist (VKA) and single VKA therapy showed the lowest risk of bleeding (8 and 12%). Unexpectedly, the highest risk of bleeding was found in women receiving a combination of low-molecular-weight-heparin (LMWH) and VKA (33%) or mono-therapy with LMWH (22%). However, this could be dose related. No difference in bleeding was found between caesarean section versus vaginal delivery (p = 0.08). In conclusion, bleeding episodes are common during pregnancy in women with mechanical heart valves receiving anticoagulant therapy. A combination of UFH and VKA or VKA monotherapy showed the lowest risk of bleeding.

High-Versus Low-Dose Warfarin-Related Teratogenicity: A Case Report and Systematic Review

OBJECTIVE

The optimal anticoagulant therapy during pregnancy in women with mechanical heart valves remains controversial. This study highlights a case of high-dose warfarin ingestion throughout pregnancy and performed a systematic review to assess rates of teratogenicity with high versus low warfarin dosing (≤5 mg daily).

METHODS

A literature search for all case reports and available literature was conducted in PubMed, Medline, and EMBASE up to December 2016 using medical subject heading terms "mechanical prosthetic valves," "pregnancy," "oral anticoagulants," "warfarin," "coumarins," "heparin, low-molecular-weight," and "thromboembolism." To be included, warfarin had to be administered anytime between 6 and 12 weeks of gestation with the dose being specified. The Newcastle-Ottawa Scale was used to assess quality of the cohort data.

RESULTS

The woman in the studied case received the highest reported warfarin doses throughout pregnancy (14.5-16.5 mg daily) and delivered a baby with no evidence of teratogenicity to the current age of 5 years. The study identified 23 case reports, with all demonstrating warfarin teratogenicity regardless of high-dose (n = 12) or low-dose (n = 11) warfarin. Twelve cohort studies identified a warfarin teratogenicity rate of 5.0%, with rates of 2.4% and 10.5% with low- and high-dose warfarin, respectively. Risk of bias was moderate (median Newcastle-Ottawa Scale score of 6) for all of the cohort studies.

CONCLUSION

Although a lower prevalence of warfarin-induced teratogenicity is reported with low-dose warfarin, a safe "cut-off" dose is misleading. Teratogenic risk with warfarin is unpredictable, mandating individual decisions regardless of the dose.

Pregnancy Outcome in Women with Mechanical Prosthetic Heart Valves Treated with Unfractionated Heparin (UFH) or Enoxaparin

OBJECTIVE

This study was carried out to determine the maternal (including thromboembolic and hemorrhagic complications) and fetal outcomes (including miscarriage, stillbirth, baby death, and live birth) in women with mechanical heart valves managed with therapeutic doses of unfractionated heparin (UFH) versus enoxaparin during pregnancy.

METHODS

This is a prospective comparative, nonrandomized study. Pregnant women with mechanical heart valves presenting to high-risk pregnancy unit of Benha University Hospital, Egypt were treated with UFH 15,000 U/12 h versus enoxaparin (Clexane) 1 mg/kg SC/12 h during pregnancy and the results were analyzed.

RESULTS

40 pregnant women were included in the study. In 20 pregnant women, anticoagulation was with UFH, and 20 pregnant women received enoxaparin. One (3 %) thrombotic complication occurred with enoxaparin treatment. Noncompliance or subtherapeutic levels contributed to this outcome in this case. Antenatal hemorrhage occurred in 4 (10 %) and postpartum hemorrhagic complications in 5 (12.5 %) pregnancies. Of the 32 pregnant women who continued after 20 weeks' gestation, 100 % (17/17) of the women taking predominantly UFH had a surviving infant compared with 93 % (14/15) of the women taking primarily enoxaparin (p = 0.25). One intrauterine fetal death occurred in the enoxaparin group. There was no significant difference in the live birth rates between the two groups (p = 0.31).

CONCLUSIONS

Compliance with therapeutic dose of UFH during pregnancy in women with mechanical heart valves is associated with a low risk of valve thrombosis and good fetal outcomes, but meticulous monitoring is essential.

Limited dose warfarin throughout pregnancy in patients with mechanical heart valve prosthesis: a meta-analysis

The continuation of warfarin throughout pregnancy in patients with a mechanical valve prosthesis is a valid anticoagulation regimen, provided that warfarin dose does not exceed 5 mg/day. Two decades after being introduced, the efficacy and safety of this regimen merit evaluation. We performed a systematic review for cases published between January 1991 and January 2013. We compiled our prospective data on 55 pregnancies and calculated pooled estimates (95% confidence interval) of adverse foetal and maternal outcomes. Events were expressed as proportions of total pregnancies, except embryopathy and maternal death, which were related to the number of live births and number of patients, respectively. There were 494 eligible pregnancies reported in 11 studies. The rate of embryopathy was 0.9% (0.4-2.4%) and most of the 13.4% (8.4-24.7%) foetal losses were due to the 12.8% (7.7-22.7%) rate of spontaneous abortion. No maternal mortality was encountered (0-1.3%) but 0.6% (0.3-2%) prosthetic valve thrombosis, 1.8% (1.1-3.6%) total thromboembolic events and 3.4% (2-5.1%) major maternal bleeding events were recorded. Foetal loss, spontaneous abortions and foetal embryopathy dropped to 8.1% (2.9-13.7%), 7.3% (3.1-11.8%) and 0.6% (0.1-2.1%) among the 344 pregnancies (69.6%) observed in the 6 prospective studies (54.5%). Prosthetic valve thrombosis (0.6%; 01-2%), total thromboembolic (2.3%; 1.2-4.6%) and major bleeding events (2.9%; 1.8-6%) remained comparable with overall results. Foetal embryopathy and prosthetic valve thrombosis were not robust on sensitivity analysis, regardless of the study design. A prospective subgroup of 96 patients (19.4%) received smaller warfarin dose, through targeting a lower international normalized ratio (INR) between 1.5 and 2.5. The associated rate of foetal loss (2.1%; 0.5-6.9%) was significantly lower than that observed in the remaining patients targeting a higher INR between 2.5 and 3.5 (16.1%; 13.1-34.4%). Adverse maternal outcomes were also fewer but rates remained comparable. Limited dose warfarin throughout pregnancy was associated with improved foetal outcomes, without jeopardizing maternal safety. Foetal outcomes were better when patients were followed up prospectively or receiving smaller warfarin doses through targeting a lower INR than recommended (1.5-2.5). Large randomized controlled trials are mandatory to evaluate our findings.