• S Gates, P Brocklehurst, and L J Davis.
• National Perinatal Epidemiology Unit, University of Oxford, Institute of Health Sciences, Old Road, Oxford, UK, OX3 7LF. simon.gates@perinat.ox.ac.uk
• Cochrane Db Syst Rev. 2002 Jan 1(2):CD001689.

BackgroundVenous thromboembolic disease (TED), although very rare, is a major cause of maternal mortality and morbidity, hence methods of prophylaxis are often used for women at risk. This may include women delivered by caesarean section, those with a personal or family history of TED and women with inherited or acquired thrombophilias (conditions that predispose people to thrombosis). Many methods of prophylaxis carry a risk of side effects, and as the risk of thromboembolic disease is low, it is possible that the benefits of thromboprophylaxis may be outweighed by harm. Current guidelines for clinical practice are based on expert opinion only, rather than high quality evidence from randomised trials.ObjectivesTo determine the effects of thromboprophylaxis in association with pregnancy in women who are pregnant or have recently delivered on the incidence of venous thromboembolic disease and side effects.Search StrategyThe register of trials maintained by the Cochrane Pregnancy and Childbirth Group, the Cochrane Controlled Trials Register, MEDLINE, EMBASE and bibliographies of reviews. Date of last search: January 2002.Selection CriteriaRandomised trials comparing one method of thromboprophylaxis with placebo or no treatment, and randomised trials comparing two (or more) methods of thromboprophylaxis.Data Collection And AnalysisData were extracted independently by all reviewers. Discrepancies were resolved by discussion.Main ResultsEight trials involving 649 women were included. Four of them compared methods of antenatal prophylaxis; low molecular weight versus unfractionated heparin (two studies), aspirin plus heparin versus aspirin alone (one study), and unfractionated heparin versus no treatment (one study). Four studies assessed postnatal prophylaxis after caesarean section; one compared hydroxyethyl starch with unfractionated heparin, two compared heparin with placebo (one low molecular weight heparin, one unfractionated heparin) and the other compared unfractionated heparin with low molecular weight heparin. It was not possible to assess the effects of any of these interventions on most outcomes, especially rare outcomes such as death, thromboembolic disease and osteoporosis, because of small sample sizes and the small number of trials making the same comparisons.Reviewer's ConclusionsThere is insufficient evidence on which to base recommendations for thromboprophylaxis during pregnancy and the early postnatal period. Large scale randomised trials of currently-used interventions should be conducted.

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