This document summarizes guidelines and studies on anticoagulation treatment for pregnant women with mechanical heart valve prostheses. It finds that oral anticoagulants (OA) appear safer for mothers but heparin appears safer for fetuses. The guidelines recommend 3 regimens: OA throughout pregnancy, substituting OA with heparin from weeks 6-13, or heparin throughout pregnancy. The document reviews 19 studies comparing outcomes of these regimens. It finds higher rates of fetal complications like embryopathy, prematurity and abortion with OA, but higher rates of maternal complications like thrombosis with heparin. The document aims to determine if fetal embryopathy risk from OA was overstated or decreasing

1. Anticoagulation of pregnant women
with mechanical heart valve
prosthesis: current guidelines
Ahmed Hassouna, MD.
March 2012

2. It is generally accepted that (OA) provide efficient
thromboprophylaxis for patients with (MPHV)
however, pregnancy raises important concerns and
addresses still unresolved questions:
 1- (OA) impose a true risk of embryopathies
and, in this regards, heparin (H) is safe for
being unable to cross the placental barrier.
 2- However, the use of (H) is associated with a
higher rate of (TEC), (VT) and maternal death.
 3- There is a considerable rate of fetal wastage,
regardless to the type of adopted regimen.
 In other words, OA appear to be safer to the
mother while H appears to be safer to the fetus!

3. In the absence of a randomized clinical trial (RCT),
AHA/ACC have recommended 3 regimen:
 1- (OA) throughout pregnancy*.
 2- (OA/H): OA are substituted with H between
the 6th and 13th week of gestation.
 3- (H) throughout pregnancy.
 In any of the above regimen it is advised to:
 1- add a daily oral dose of 100 mg aspirin.
 2- Shift to (H) therapy before delivery (2 weeks- 2 days) and,
 3- Hospitalization for either normal or induced delivery at 36th month.

4. A Medline search was conducted of articles published in English
language between January 2000 and September 2009 using MESH
headings “PHV", "pregnancy,” and “anticoagulants.”
Inclusion/exclusion criteria: Major adverse outcomes:
-Complete reports of (MPHV) patients  Maternal adverse outcomes included :
that defined any of the 3 PVT, TEC, major bleeding and death.
anticoagulation regimen, as well as a
4th group of concomitantly reported
 Fetal adverse outcomes included: fetal
cases who stopped anticoagulants embryopathy/congenital malformation,
against medical advice. spontaneous abortions, prematurity
 -Articles involving small case series of and total fetal wastage.
less than 5 patients, reports to  Outcomes were expressed as
questionnaire, duplicate data, letters to proportions of total pregnancies,
the editor as well as data issued from except embryopathy and maternal
editorials or review articles were death, which were related to the
excluded from the analysis. numbers of live births and number of
 *The quality of given information was patients; respectively.
appreciated by noting if eligible studies
were clinical trials, prospective  Results were presented as pooled
observational studies or else. estimates (+ 95% confidence interval).

5.  1. Rowan JA, McCowan LM, Raudkivi PJ, North RA. Enoxaparin treatment in women with mechanical heart valves during
pregnancy. Am J Obstet Gynecol. 2001;185(3):633–637.
 2. Hassouna A, Allam H. Oral anticoagulation therapy during pregnancy in patients with mechanical mitral valves: a prospective
study. Cardiovasc Surg. 2001;9(5):478–481.
 3. Ashour ZA, Shawky Abdel Fattah H, Hassan HM. Outcome of pregnancy in women with mechanical valves. Tex Heart Inst J.
2002;27:240–245.
 4. Geelani MA, Singh S, Verma A, Nagesh A, Betigeri V, Nigam M. Anticoagulation in patients with mechanical valves during
pregnancy. Asian Cardiovasc Thorac Ann. 2005;13(1):30–33.
 5. Yamak B, Emir M, Ulus TA, et al. Pregnancy with St. Jude medical mitral valve prosthesis. Asian Cardiovasc Thorac Ann.
2000;8:127–129.
 6. Ayhan A, Yucel A, Bildirici I, Dogan R. Feto-maternal morbidity and mortality after cardiac valve replacement. Acta Obstet
Gynecol Scand. 2001; 80(8):713–718.
 7. Al-Lawati AA, Venkitraman M, Al-Delaime T, Valliathu J. Pregnancy and mechanical heart valves replacement; dilemma of
anticoagulation. Eur J Cardiothorac Surg. 2002;22(2):223–227.
 8. Cotrufo M, De Feo M, De Santo LS, et al. Risk of warfarin during pregnancy with mechanical valve prostheses. Obstet Gynecol.
2002;99:35–40.
 9. Srivastava AK, Gupta AK, Singh AV, Husain T. Effect of oral anticoagulant during pregnancy with prosthetic heart valve. Asian
Cardiovasc Thorac Ann. 2002;10(4):306–309.
 10. Bhutta SZ, Aziz S, Korejo R. Pregnancy following cardiac surgery. J Pak Med Assoc. 2003;53:407.
 11. Vural KM, Ozatik MA, Uncu H, et al. Pregnancy after mechanical mitral valve replacement. J Heart Valve Dis. 2003;12(3):370–
376.
 12. Nassar AH, Hobeika EM, Abd Essamad HM, Taher A, Khalil AM, Usta IM. Pregnancy outcome in women with prosthetic heart
valves. Am J Obstet Gynecol. 2004;191:1009–1013.
 13. De Santo LS, Romano G, Della Corte A, Tizzano F, Petraio A, Amarelli C. Mitralmechanical replacement in young rheumatic
women: analysis of longterm survival, valve-related complications, and pregnancy outcomes over a 3707-patient-year follow-up. J
Thorac Cardiovasc Surg. 2005;130(1):13–19.
 14. Plesinac SD, Darko PV, Pilic IZ, Babovic IR. Anticoagulation therapy during pregnancy of patients with artificial heart valves:
fetomaternal outcome. Arch Gynecol Obstet. 2006;274(3):141–145.
 15. Akhtar RP, Abid AR, Zafar H, Cheema MA, Khan JS Anticoagulation in pregnancy with mechanical heart valves: 10-year
experience. Asian Cardiovasc Thorac Ann2007;15(6):497–501.
 16. Kawamata K, Neki R, Yamanaka K, et al. Risks and pregnancy outcome in women with prosthetic mechanical heart valve
replacement. Circ J. 2007; 71(2):211–213.
 17. Khamooshi AJ, Kashfi F, Hoseini S, Tabatabaei MB, Javadpour H, Noohi F. Anticoagulation for prosthetic heart valves in
pregnancy. Is there an answer? Asian Cardiovasc Thorac Ann. 2007;15(6):493–496.
 18. Kim KH, Jeong DS, Ahn H. Anticoagulation in pregnant women with a bileaflet mechanical cardiac valve replacement. Heart
Surg Forum. 2007; 10(4):E267–E270.
 19. Lee JH, Park N, Keum DY, Choi SY, Kwon KY, Cho CH. Low molecular weight heparin treatment in pregnant women with a
mechanical heart valve prosthesis. J Korean Med Sci. 2007;22:258–261.

6. Distribution of mechanical prosthetic heart valves
Number Number of Number Type of mechanical prosthesis Position of implantation
of patients/ of Cage Tilting bileaflet undefined mitral Aortic Mitral + tricuspid
studies* pregnancies prostheses & ball disc aortic
14 745/988 866 134 272 220 240 515 107 122+122 -
(82.3%) (77.8%)
3 147/243 247 - 110 121 16 156 34 25+25 7
(17.7%) (22.2%)
17 892/1231 1113 134 382 341 256 671 141 147+147 7
(12%) (34.3%) (30.6%) (23%) (60.3%) (12.7%) (26.4%) (0.6%)
 *= A total of 19 studies were included in our review (974 patients/ 1343 pregnancies) however, 2 studies (1- Bhutta SZ, Aziz S, Korejo R.
Pregnancy following cardiac surgery. J Pak Med Assoc. 2003;53:407. 2- De Santo LS, Romano G, Della Corte A, Tizzano F, Petraio A, Amarelli C.
Mitral mechanical replacement in young rheumatic women: analysis of long-term survival, valve-related complications, and pregnancy
outcomes over a 3707-patient-year follow-up. J Thorac Cardiovasc Surg. 2005;130(1):13–19.) do not appear in this table because no
information was available to correlate both: the exact number and positions of implanted MPHV.

7. Anticoagulation regimens adopted / compared per study.
Oral anticoagulation regimen* Number of Number of Number of
studies patients pregnancies
A) Studies adopting a single regimen
1- OA 4 (21%) 154 (15.8%) 182 (13.6%)
2- OA/H 1 (5.3%) 45 (4.6%) 64 (4.8%)
3- Heparin 2 (10.5%) 23 (2.4%) 30 (2.2%)
total 7 (36.9%) 222 (22.8%) 276 (20.6%)
B) Studies comparing different regimens
4- OA versus OA/H 5 (26.3%) 434 (44.5%) 593 (44%)
5- OA versus Heparin 2 (10.5%) 104 (10.7%) 148 (11%)
6- OA versus OA/H versus Heparin 2 (10.5%) 60 (6.2%) 123 (9.2%)
7- OA versus OA/H versus none 1 (5.3%) 21 (2.15%) 21 (1.6%)
8- OA versus Heparin versus none 1 (5.3%) 101(10.4%) 136 (10.1%)
9- OA vs. OA/H vs. Heparin vs. none 1 (5.3%) 32 (3.3%) 46 (3.4%)
total 12 (63.1%) 752 (77.2%) 1067 (79.4%)
Overall total 19 974 1343

8. Distribution of anticoagulation regimen

9. Adverse fetal outcomes
Anticoagulation regimen*
OA OA/H Heparin None
(559/833) (258/322) (96/157) (27/31)
Embryopathy/ 21/559 (3.7%) 1/258 (0.4%) 0/96 0/27
malformations [1.9-4.8] [0.2-2.7] [0-3.1] [0-11.1]
Prematurity 62/833 (7.4%) 26/322 (8.1%) 15/157 (9.5%) 3/31 (9.7%)
[2.1-9.6] [3.4-12.8] [3-23.6] [2.6-22.8]
Spontaneous 194/833 (23.3%) 42/322 (13%) 34/157 (21.6%) 2/31 (6.4%)
abortion [13.8-31.6] [7-21.6] [10.1-29.8] [1.8-20.7]
Fetal wastage 274/ 833 (32.9%) 64/ 322(19.9%) 61/157 (38.8%) 4/31 (12.9%)
[25.7-49.2] [15.9-31.4] [32-46.8] [5-28.4]

10. Adverse maternal outcomes
Anticoagulation regimen*
OA OA/H Heparin None
(559/833) (258/322) (96/157) (27/31)
PVT 10/833 (1.2%) 17/322 (5.3%) 16/157 (10.2%) 8/31 (25.8%)
[0.7-2.2] [3-10.8] [6.9-16.5] [0.2-88.2]
TEC 24/833 (2.9%) 23/322 (7.1%) 21/157 (13.4%) 9/31 (29%)
[1.9-4.1] [4.7-10.3] [9.7-20.5] [0.5-98.7]
Maternal 35/833 (4.2%) 11/322 (3.4%) 17/157 (10.8%) 2/31 (6.4%)
bleeding [1.4-6.8] [2.3-6.6] [2.8-27.3] [1.8-20.7]
Maternal 7/605 (1.1%) 4/236 (1.7%) 5/107 (4.7%) 0/26
mortality [0.5-2.2] [0.8-4.5] [2.2-10.7] [0-11.5]

11. Adverse outcomes reported in prospective studies
Adverse outcomes Anticoagulation regimen
OA OA/H Heparin
(182/215) (87/100) (47/80)
A) Fetal:
Embryopathy/congenital (0.5%) 0 0
malformations
Prematurity (14.9%) (13%) (1.2%)
Spontaneous abortion (10.2%) (8%) 20 (25%)
Fetal wastage due to any (15.3%) (13%) (41.2%)
cause
B) Maternal
PVT 0 (1%) (7.5%)
TEC (2.3%) (4%) (12.5%)
Maternal bleeding (3.2%) (2%) (1.2%)
Maternal mortality 0 (1%) (7.8%)

12. Questions to be answered
 1- OA induced embryopathy: was it
overstated or is it actually decreasing?
 2- Does Heparin really improve fetal
wastage, even on the expense of mothers?
 3- Is pregnancy becoming safer for patients
with MPHV?

13. Was fetal embryopathy overstated or is it
actually decreasing?
 In their excellent large meta-analysis that reviewed
the subject over the last 3 decades of the 20th
century, Chan and colleagues have shown pooled
risks of embryopathy of 6.4% and 3.4% in patients
following OA and OA/H regimen; respectively (Arch
Intern Med. 2000;160(2):191–196). In our study, the
calculated pooled risk has dropped to 3.7% in
patients on (OA), and became negligible (0.4%) in
patients on OA/H.
 Twenty years ago, Cotrufo and co-workers have
suggested that warfarin can be safe if the dose can
be restricted to 5mg/day (Eur J cardiothorac Surg.
1991;5:300–305), yet it is unclear and hence
doubtful if the patients reported in Chan review have
benefited from this information.

14.  On the contrary, most of our authors have
clearly indicated adopting this strategy.
Consequently, we find it legitimate to suppose
that the risk of warfarin embryopathy may be
actually decreasing; even if actual
doses/success in adopted strategy are not
usually reported.
 Playing the same tune, this awareness can also
explain the very low risks of 0.5% and 0%
recorded in our prospective subgroup of
patients.

15. Does heparin improve fetal wastage?
The salutary effect of introducing heparin during the 1st trimester
is lost/reversed whenever its use is extended till parturition.

16. Is pregnancy becoming safer for patients with MPHV?
Compared to older reviews, maternal complications (mainly TEC) appear to
be decreasing by nearly 50% which may reflect the improving valve
technology (40% vs. 12% cage and balls valves). However, the use of
heparin was associated with the same crescendo pattern; which was also
reported in prospective studies.

17. The dilemma of using heparin
 The inherent problem of small series: Out of the
1,343 pregnancies and the 19 series in this review,
only 11.7% of patients were following heparin
throughout pregnancy in as many as 42% of our
eligible series.
 In this review, the largest series of pregnant
women who were kept on UFH and LMWH did only
include 66 and 14 pregnancies; respectively. This
modest representation may be due to a tendency
for the publication of case reports, which we
automatically excluded from our analysis.
 On the other hand, the reluctance to include many
patients in those studies may suggest a probable
loss of confidence in the safety of heparinotherapy.

18. The dilemma of using heparin (cont.)
 Two unfinished clinical trials are likely to
overshadow any serious decision: Salazar and co-
workers reported the interruption of their trial on
UFH because of the unacceptable maternal
mortality due to TEC and the manufacturer of
Lovenox launching a warning against its use during
pregnancy in patients with PHV because of its
association with serious maternal and fetal
complications, even if this was soon rephrased to
‘‘use of Lovenox for thromboprophylaxis in
pregnant women with mechanical PHV has not
been adequately studied’’

19. The dilemma of using heparin (cont.)
 There is an overall inadequate reporting of data
concerning key elements, namely patient compliance,
adequate dosing, and regular adjustment. In the largest
series, which included 42% of pregnancies on Heparin,
UFH was given in a small dose of 5,000 IU/8 h to 10000
IU/12 h, and the activated PTT was never checked
[Ashour et al; Tex Heart Inst J. 2002]. The other 7
series reported between 2-18 pregnancies managed
with UFH, LMWH, or IVIH, with only one prospective
study on LMWH [Rowan et al; Am J Obstet. Gynecol.
2001], which respected and, fortunately, reported the
recommended levels of pre- and 4-h postdose anti-Xa
monitoring.

20. CONCLUSION
 This study shows that (OA) and (OA/H) are still
competing alternatives for pregnant ladies with
(MPHV), especially with an apparently decreasing rate
of fetal embryopathy.
 (Heparin) does not ensure better fetal outcomes and is
still associated with the worst adverse maternal
outcomes, including mortality.
 To the best of our knowledge, still the literature do not
supply enough data to judge the adequacy of dose
adjustment of heparin or to evaluate the protective
effect of an adjuvant low-dose aspirin in conjunction
with either therapy.