VTE prophylaxis in pregnant people with chronic physical disability: Data from a physicians survey and the need for guidance

Introduction

Venous thromboembolism (VTE) complicates around 0.5–2.2 per 1000 pregnancies and remains one of the leading causes of maternal mortality and significant maternal morbidity in the developed countries.^1,2

The risk of VTE is four to five times higher in pregnant women than in non-pregnant women of the same age. This risk increases by 15- to 35-fold during the postpartum period when compared to age-matched non-pregnant women. ³ Most women with VTE in pregnancy had risk factors which developed during pregnancy or were present prior to pregnancy. ⁴ Therefore, risk assessment for VTE during pregnancy is recommended. Those identified at higher risk of VTE are offered thromboprophylaxis with low molecular weight heparin (LMWH).^4,5 Presence of a single risk factor can only have a modest effect on VTE risk and may not reach an absolute risk of 1% to recommend thromboprophylaxis, as recommended by Canadian guidelines, whereas a combination of risk factors may increase the absolute risk of VTE. ⁴

Immobility is a concern for some individuals with physical disabilities, and is a risk factor for VTE. ⁶ The International Classification of Functioning, Disability and Health (ICF) advanced the understanding and measurement of functioning and disability as a dynamic interaction between functioning, health conditions and contextual factors either personal or environmental. It is therefore defined by The World Health Organization (WHO) as “impairments, activity limitations, and participation restriction”. ⁷

The global prevalence of disability in women in the reproductive age group is estimated to range between 6.4% to 12%. In the US, around 10.206 million (10%) women in this age group were classified as having a disability in 2018. ⁸ Out of these 5.204 million (5%) have a physical disability. The conditions giving rise to physical disability are extremely diverse. They can be present from birth (such as spina bifida or cerebral palsy) or result from trauma (like spinal cord injury) or an underlying medical condition. They may be progressive or stable, and involve different degrees of immobility. ⁹

Although larger population registries are lacking, smaller studies indicate that the women with chronic physical disability (CPD) can conceive with successful pregnancy outcomes. The number of pregnancies in people with disability is increasing.^10,11 However, these women remain at risk of adverse outcomes during pregnancy such as preterm birth and pre-eclampsia. They also have a higher incidence of caesarean section.^12,13 Additional aids may be required during pregnancy. Increased incidence of smoking, depression and underlying medical disorders such as diabetes and obesity have also been observed in these women.^11,14,15 Women with spinal cord injury (SCI) can develop additional complications during pregnancy including urinary tract infections, pressure ulcers, autonomic dysreflexia which can further impair their mobility.^12,16–18 Recovery during the postpartum period may be affected with prolonged inpatient stay due to complications during pregnancy, intrapartum or postpartum. ¹⁵

Several gaps in care of pregnancies in people with CPD have been highlighted in literature due to lack of clinical trials and scarcity of consensus based recommendation and interprofessional collaboration.^19,20

Although a number of people with CPD develop risk factors for increased VTE risk in pregnancy, literature on VTE rates remains limited. It is unknown how chronic physical disability itself, independently from underlying comorbidities such as bladder infections, impacts the risk of VTE in pregnancy. VTE risk assessment and therefore prevention during pregnancy for people with CPD can be challenging, and there remains a lack of consensus guidelines on thromboprophylaxis for people with CPD during pregnancy.

As per the current American Society of Hematology (ASH) guidelines, thromboprophylaxis would be offered to people with an absolute risk threshold of greater than 2% in the antepartum period and greater than 1% in the postpartum period. ⁴ Other guidance documents recommend risk assessment in women with disability and following local thromboprophylaxis protocols. ²¹ But data on physician practices on thromboprophylaxis during pregnancy with CPD are limited.

Therefore, this study sought to understand the current approach of Canadian physicians for prevention of VTE in pregnant people with CPD.

To our knowledge, this is the first survey addressing VTE prophylaxis for pregnancies in people with CPD.

Materials and methods

Results

The survey was active from August 2019 to November 2019. During this time, 73 participants responded to the survey, and 55 (75.3%) completed the survey. There were 18 incomplete surveys (24.7% of total responses), which were excluded from the analysis.

Table 1 describes the demographics of the physicians who responded to the survey. The survey sample consisted of 33 (60%) MFM specialists, and 22 (40%) IM specialists: 14 (25.5%) Hematologists and eight (14.5%) GIM physicians. Participants were primarily from Province of Ontario (58.2%), and the majority reported assessing less than five (94.5%) women with CPD during antepartum or postpartum period, yearly. Other participants were from British Columbia 11(20%), five (9%) each from Quebec and Nova Scotia respectively and one (1.8%) each from Saskatchewan and Manitoba. The majority of respondents had over 20 years of practice (35.2%), and nine had less than 5 years of practice (16.67%). There was similar distribution of male (45.5%) and female respondents (49%).

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Table 1.

Demographics of the physician participants.

	Frequency: n
Province of practice
British Columbia	11
Manitoba	1
Nova Scotia	5
Ontario	32
Quebec	5
Saskatchewan	1
Specialty
Maternal Fetal Medicine	33
Hematology	14
Internal Medicine	8
Years of practice
<5 years	9
5-10 Years	12
11-15 Years	7
16-20 Years	7
>20 Years	19
Gender
Male	25
Female	27
Prefer not to answer	3
Number of pregnant people using wheelchairs or with limited mobility seen in past year
0-5	38
6-20	12
21-50	4
50-100	0
>100	1
Number of pregnant people using wheelchairs or with limited mobility seen in past year
0-5	52
6-20	2
21-50	1
50-100	0
>100	0

Only 18% (4/22) IM Specialists report being uncomfortable managing VTE prophylaxis during pregnancy with a CPD, whereas 54.5% (12/22) of IM Specialists were comfortable, and 27.3% (6/22) were neither comfortable nor uncomfortable. Similarly, 18.2% (6/33) of MFMs felt uncomfortable and more than half the MFM Specialists (60.6%) (20/33) felt comfortable managing VTE.

Overall, 58% (32/55) of the total number of respondents were confident and less than a quarter (10/55) felt uncomfortable offering VTE prophylaxis.

Concordance was noted between the respondent's comfort levels and their request for Hematology consultation for VTE prophylaxis during pregnancy.

Half of the IM Specialists agreed that women with CPD did not require the need for a consultation with Hematology during pregnancy (11/22). MFM Specialists had mixed views; a quarter (24.5%) did not refer to a Hematologist during pregnancy and just over a quarter (33.3%) would consider referring to a Hematologist When Hematologists were assessed independently of GIM, only 7% Hematologists (1/14) considered referral to Hematology for VTE prophylaxis to be appropriate.

More than 75% (43/55) of the physicians who responded were interested in formal education on the topic. Only 20% (10/55) of respondents were uncomfortable managing VTE prophylaxis during pregnancy. Guidelines (42/55) were the most popular method of education on this topic, followed by rounds (21/55) and an online learning module (15/55).

To assess how physicians would manage thromboprophylaxis in the context of chronic physical disability and pregnancy, four separate clinical scenarios were presented. More than one response could be submitted.

Scenario 1 involved a pregnant young person using a wheelchair for limited mobility. Overall, 81.8% (18/22) of IM Specialists would not offer antepartum antithrombotic therapy in this scenario. (Figure 1). However, the majority of MFM Specialists (72.7%, 24/33) would offer prophylactic thromboprophylaxis during the antepartum period and more than 75% (26/33) would also consider the chronic physical disability as the only risk factor for VTE and offer thromboprophylaxis in the postpartum period. 36.4% (8/22) of IM specialists would offer postpartum VTE prophylaxis if the use of a wheelchair was the only risk factor, 27.3% (6/22) would offer thromboprophylaxis if there was one other risk factor and 22.7% (5/22) would offer no postpartum VTE prophylaxis.

In Scenario 2, which involved a young person with a longstanding physical disability using a walking aid who had moved to using wheelchair during pregnancy, 75% of MFM Specialists (25/33) would offer antepartum and more than half postpartum VTE prophylaxis (21/33) (Figure 2). In comparison, approximately 75% of IM Specialists (16/22) would not offer antepartum VTE prophylaxis but nearly half (10/22) would offer VTE prophylaxis after delivery.

In Scenario 3, which involved a young person with pregnancy within a year of spinal cord injury was considered at higher risk of VTE. Most of the respondents selected antithrombotic prophylaxis during pregnancy and the postpartum period (Figure 3).

In Scenario 4, which involved a young person with a longstanding physical disability using a walking aid regularly and occasionally uses wheelchair, now pregnant, the majority of physicians considered this person to be at low risk of VTE during antepartum period and would not offer antithrombotic therapy during pregnancy (Figure 4).

Discussion

The risk of, and management of VTE in pregnancy for people with a CPD is not well understood. This survey of Canadian physicians demonstrated substantial variation in the respondent's views regarding VTE prophylaxis in the antepartum and postpartum period. The difference in antithrombotic management may reflect knowledge, experience, and/or agreement with various national guidelines. The Society of Obstetricians and Gynecologists of Canada recommends antenatal and postpartum thromboprophylaxis for any individual who has an absolute risk of VTE of greater than 1% but does not mention CPD in their list of risk factors. ⁶ The Royal College of Obstetricians and Gynecologists Guideline from 2015 includes paraplegia as a risk factor for VTE, however does not recommend thromboprophylaxis if this is the only risk factor. ²³

Lack of consensus regarding thromboprophylaxis in general during pregnancy has previously been illustrated in the literature: a cohort study of 293 people who had undergone caesarean delivery were assessed to see if they would have received thromboprophylaxis if the Royal College of Obstetricians and Gynecologists, UK (RCOG), Chest or American College of Obstetrics and Gynecology (ACOG) guidelines were followed, and discovered a rate of 85%, 35%, or 1% respectively. ²⁴

Outside of pregnancy, thromboprophylaxis for individuals with physical disabilities is only suggested in specific settings, such as in the scenario of acute SCI, ²⁵ when people with SCI are hospitalised or have a surgical procedure ²⁶ or in the scenario of a person with a neurological impairment experiencing sudden immobility. ²⁷ In our study, the increased agreement surrounding thromboprophylaxis in the clinical scenario of a pregnancy in the first year of an SCI may be reflective of this knowledge.

While no large-scale studies have assessed the benefit of anticoagulation in the prevention of VTEs in people with CPD during pregnancy, they appear to have increased risk of VTE. In a large retrospective study comparing 529 pregnant people with spinal cord injury, paralysis or spina bifida to 5282 pregnant people without, the RR of VTE was 9.16 (CI 2.17−38.60). ²⁸ Other cohort studies including pregnancies in people with SCI have reported VTE rates of 3−8%.^12,29 However, these women have higher rates of perinatal complications including preterm birth and stillbirth, urinary tract infection, longer and more frequent hospitalization, and higher rates of medical risk factors for VTE such as obesity and diabetes,^14,19 and it is difficult to assess if the observed increased risk in these studies is due to chronic physical disability alone or other factors.

Not all physicians are comfortable with VTE management of pregnant people with CPD, which is reflected in the lack of overall consensus. However, an important key finding of this study is that there is a desire to learn more about VTE prophylaxis during pregnancy, and it appears that a guideline would be the preferred method of communication. A need for education in the intersection of obstetrics and physical disability has previously been illustrated among Canadian obstetrics and gynecology residents. ³⁰

We recognize the study has some limitations. Scenario-based questionnaires have inherent limitations such as reporting bias where data may not correlate with physician's behavior. We have attempted to minimize these limitations by developing scenarios that closely simulate real patients. The scenarios were pilot tested to ensure relevance to the physicians. It is possible that local factors, such as cost, may influence the selection of anticoagulant agent during pregnancy. As with many survey responses, our overall response rate appears low, however the number of physicians who have an interest in caring for this unique population is unknown but is also likely quite low.

Conclusion

Despite the above limitations, data from our study suggests that the approach towards thromboprophylaxis in pregnancy in people with CPD was variable and that most MFM specialists were comfortable with starting VTE prophylaxis. Also, MFM specialists appear to be more likely to consider thromboprophylaxis than IM physicians.

The variation in responses calls for larger studies to better understand the risk and prevention of VTE in pregnancy in people with CPD. In light of the absence of randomised controlled trials (RCT), a further step forward on this subject would be the use of the Delphi method to generate consensus guidance which may improve the care provided to people with CPD during pregnancy. To better manage this complex population, CPD should be taken into consideration as a risk factor for development VTE in future guidance.