[Transvaginal bleeding in pregnancy, as risk factor of Rhesus-D antigen isoimmunization]

The aim of the present study was to evaluate transvaginal bleeding (TVB) as a risk factor for Rhesus isoimmunization during pregnancy, in order to optimize the application of Anti-D gammaglobulin in non-immunized pregnant women, as an alternative to the routine application of Anti-D at 28 weeks of gestation.

This case-control study was conducted from 1995 to 2001 at Mexico's National Perinatology Institute. Cases (n = 24) were non-immunized pregnant women who showed positive anti-D antibody seroconversion during pregnancy or during the early puerperium. Controls (n = 24) were non-immunized pregnant women who enrolled after each case, with similar clinical characteristics but who had no anti-D antibody seroconversion during pregnancy. In all cases the newborns were Rh-positive. None of the patients received immunoprophylaxis at 28 weeks of gestation. The presence of TVB was recorded at any stage of pregnancy and before labor. Odds ratios with 95% confidence intervals were used to assess associations.

TVB was observed in 18/24 (75%) cases and in 5/24 (20%) controls. Preterm uterine contractions and threatened miscarriage were the most frequent causes of TVB. The presence of one TVB event during pregnancy increased 11.4 times (95% CI 2.9-44.0) the likelihood of Rhesus isoimmunization. TVB after 20 weeks of gestation increased the likelihood 5.0 times (95% CI 1.3-19.1). TVB before 20 weeks of gestation was not significantly associated with Rh isoimmunization (OR = 7.6, 95% CI 0.8-69.5).

Prophylaxis with anti-D gammaglobulin should be given to all non-immunized Rhesus-negative pregnant woman with TVB at any stage of pregnancy. The English version of this paper is available at:http://www.insp.mx/salud/index.html.