Dose-dependent fetal complications of warfarin in pregnant women with mechanical heart valves
Key result
Warfarin > for mechanical valves during pregnancy is linked to more fetal complications.
- P=0.0001
- n=43
Why the study?
Gravid patients with mechanical heart valves require long-term anticoagulation, but the dose-dependent risk of warfarin fetal complications is uncertain.
Key Points
- To determine the incidence of fetal complications associated with warfarin therapy during pregnancy and evaluate whether these risks are dose-dependent.
- Observed 43 women across 58 pregnancies on warfarin therapy targeting an international normalized ratio (INR) of 2.5 to 3.5.
- Scheduled planned caesarean sections at the 38th week with brief warfarin cessation to avoid maternal and fetal hemorrhage.
- Categorized and analyzed fetal complications by maternal warfarin dosage (≤5 mg/day vs. >5 mg/day).
- Recorded 31 healthy babies (30 full term, 1 premature) and 27 fetal complications, including 22 spontaneous abortions, 2 warfarin embryopathies, 1 stillbirth, 1 ventricular septal defect, and 1 growth retardation.
- Observed significantly more fetal complications in pregnancies exposed to warfarin doses >5 mg (22 complications) than doses ≤5 mg (5 complications; p = 0.0001).
- Identified two cases of maternal valve thrombosis, with no instances of maternal or fetal bleeding during delivery.
Study Design
Type
Cohort (n=43)
PICO
P
Population
43 pregnant women with mechanical heart valves on warfarin therapy carrying out 58 pregnancies.
E
Exposure / Comparator
Warfarin dosage > 5 mg vs Warfarin dosage <= 5 mg
O
Primary Outcome
Fetal complications, p=0.0001
Main Result
p-value: p=0.0001
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Key expert perspectives
Captured external expert commentary on this paper, strongest first. Original sources are linked where available.
“the results clearly suggest that the detrimental effect of a VKA on fetal outcome is not limited to the first trimester.”
RDRaffaele De CaterinaCardiologist, anticoagulation expert, ESC panel member
“We are aware that the recent ESC guidelines on the 'management of valvular heart disease' favour the use of VKAs (warfarin) if the maintenance dose is relatively low (5 mg/day) also in the first trimester of pregnancy, but this recommendation is based on data from studies of small cohorts of patients.”
KMKarl MischkeCardiologist, RWTH Aachen University
“The risk of warfarin embryopathy is probably dose-dependent. The current ESC guideline on management of valvular heart disease published in this journal in January 2007 therefore favours the use of warfarin during the first trimester if the dose is 5 mg/24 h.”
Implication
Warfarin dose >5 mg may raise fetal risk in mechanical valve pregnancies; supports dose-stratified counseling but leaves optimal regimen open.
Abstract
OBJECTIVES: The purpose of this study was to assess the incidence of warfarin fetal complications and whether they are dose-dependent. BACKGROUND: Gravid patients with mechanical heart valves require long-term anticoagulant therapy. Controversy exists concerning the appropriate treatment of these patients. METHODS: Forty-three women on warfarin carrying out 58 pregnancies were studied. For each patient with full-term pregnancy a caesarian section was scheduled for the 38th week during brief warfarin discontinuation. Maternal and fetal complications were evaluated. Fetal complications were divided according to the warfarin dosage < or = 5 mg and > 5 mg necessary to keep an international normalized ratio (INR) of 2.5 to 3.5, and analyzed subsequently. RESULTS: A total of 58 pregnancies were observed: 31 healthy babies (30 full term, 1 premature) and 27 fetal complications (22 spontaneous abortions, 2 warfarin embryopathies, 1 stillbirth, 1 ventricular septal defect, 1 growth retardation) were recorded. Two maternal valve thromboses occurred. No fetal or maternal bleeding was observed during caesarian sections or premature vaginal delivery. Patients whose warfarin doses during pregnancy were > 5 mg had 22 fetal complications, whereas those taking a dose < or = 5 mg had only five fetal complications (p = 0.0001). For an increase of the warfarin dose there was a substantially increased probability of fetal complications (p < 0.0001; p < 0.7316). CONCLUSIONS: There is a close dependency between warfarin dosage and fetal complications. Patients on warfarin anticoagulation may be delivered by planned caesarian section at the 38th week while briefly interrupting anticoagulation.
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Cite This Study
Vitale et al. (1999) conducted a cohort in Pregnant women with mechanical heart valves (n=43). Warfarin dosage > 5 mg vs. Warfarin dosage <= 5 mg was evaluated on Fetal complications (p=0.0001). Warfarin dosage > during pregnancy in women with mechanical heart valves was associated with more fetal complications compared to doses ≤.