Deep vein thrombosis and pregnancy: heparin does not clearly prevent recurrence.

Clinical bottom line (level 1b-)

  1. Pregnant women with a history of deep vein thrombosis who are given heparin, have no clear difference in preventing a further DVT than those not given anything, with a wide confidence interval.
  2. The effect on abortion, placental abruption, preterm labour and osteopenia is unclear.
Howell et al: British Journal of Obstetrics and Gynaecology 1983; 90: 1124-1128
Expires May 2003

The study

Unblinded concealed randomised trial with intention-to-treat
Setting: university maternity hospital, UK

40 patients (aged mean 30 years, 100% female) pregnant and a documented history of deep vein thrombosis
Note:
  • Patients were followed until term.
  • All patients received postpartum thromboprophylaxis.


    • Control Group: (n = 20, 20 analysed): no treatment
    Experimental Group: (n = 20, 20 analysed): heparin subcutaneously 10,000 units twice daily during pregnancy and labour (titrated so dose was <0.4 units/ml)

    100% followed for ?

    The evidence

    Outcome Time to outcome CEREERRRR
    (95% CI)    		ARR
    (95% CI)    		NNT
    (95% CI)
    abortion unknown 1
    (5.00%)    		 1
    (5.00%)    		 0%
    (-1400% to 93%)    		 0.00%
    (-13.5% to 13.5%)    		 inf
    (NNT = 7 to infinity;
    NNH = 7 to infinity)
    placental abruption unknown 0
    (0.00%)    		 1
    (5.00%)    		 %
    (% to %)    		 -5.00%
    (-14.6% to 4.55%)    		 -20
    (NNT = 22 to infinity;
    NNH = 7 to infinity)
    deep vein thrombosis unknown 1
    (5.00%)    		 0
    (0.00%)    		 100%
    (% to %)    		 5.00%
    (-4.55% to 14.6%)    		 20
    (NNT = 7 to infinity;
    NNH = 22 to infinity)
    preterm labour unknown 3
    (15.0%)    		 3
    (15.0%)    		 0%
    (-340% to 77%)    		 0.00%
    (-22.1% to 22.1%)    		 inf
    (NNT = 5 to infinity;
    NNH = 5 to infinity)
    osteopenia unknown 0
    (0.00%)    		 1
    (5.00%)    		 inf%
    (-300% to inf%)    		 -5.00%
    (-14.6% to 4.55%)    		 -20
    (NNT = 22 to infinity;
    NNH = 7 to infinity)

    Comments

    1. The study is too small to show any potential benefit or harm from using heparin.
    2. Uncertain how deep vein thrombosis was diagnosed during pregnant.

    Citation

    1. Howell R, Fidler J, Letsky E: The risks of antenatal subcutaneous heparin prophylaxis: a controlled trial. British Journal of Obstetrics and Gynaecology 1983; 90: 1124-1128
    Contributor: Chris Ball and Clare Wotton, May 2000
    Reviewer: Khalid S Khan

    Clinical Question.
    Patient pregnant and a history of DVT
    Intervention or Exposure heparin
    Comparison no treatment
    Outcome abortion or DVT