Anticoagulation: LMWH is safe in pregnancy

Clinical bottom line (level 3b)

  1. Pregnant women who receive LMWH compared with no treatment may be at increased risk of a pre-term delivery, but are not clearly more likely to have a malformed baby, a low birth weight baby, or a stillbirth.
Sorensen et al: Acta Obstet Gynecol Scand 2000; 79 : 655-659
Expires November 2003

The study

Case-control study with objective outcomes, adjusted for confounding factors, not validated in an independent set of patients.

Setting:

17325 patients women giving birth to a live singleton
Cases: 66 patients (0% , mean age ): received low-molecular-weight heparin: 91% dalteparin
Controls: 17259 patients (0% , mean age ):

Factors studied:
  • maternal age, birth order, gestational age, smoking, LMWH

    Factors summarised:
  • LMWH

    Multiple regression analysis was used to adjust for confounding factors.

    Outcomes studied:
  • pre-term delivery
    • Data on congential defects was collected from the Danish Medical Birth Registry

    The evidence

    Patient expected event rate for pre-term delivery: 5.7%
    risk factor for
    pre-term delivery     		adjusted OR
    (95% CI)    		 NNH
    (95% CI)
    LMWH 2.11
    (0.96 to 4.65)     		18
    (-460 to 6)

    • No association between LMWH and malformation, low birth weight or stillbirth was found. Odds ratios were not reported.

    Comments


    Citation

    1. Sorensen HT, Johnsen S, Larsen H, et al: birth outcomes in pregnant women treated with low-molecular-weight heparin. Acta Obstet Gynecol Scand 2000; 79 : 655-659
    Search Terms: from ACP Journal Club other articles noted
    Contributor: Chris Ball, November 2001
    Reviewer:

    Clinical Question.
    Patient pregnant women
    Intervention or Exposure low-molecular-weight heparin
    Comparison no treatment
    Outcome malformations, low birth weight, still birth, pre-term delivery
    		•