Nicole: I think perhaps you are confusing giving anti-D prophylactically (usually given once at 28weeks if antibody negative and then again postnatally if the baby is Rh pos) with treating a possible sensitising event.
When given prophylactically the "life" of the antibodies is thought to be around 12 weeks, theoretically should a sensitising event occur in this time period then these antibodies will take care of it. If the event were significant then perhaps another dose would be given with appropriate blood work (antibodies etc.. and FCAD). When treating a possibly sensitising event: when foetal blood cells would mix with maternal ones eliciting and immuune response and hence a "memory" in the mother's immune system which would make her sensitised then the time period is 3 days or 72hrs. This time period is not the life of the antibodies but the time interval within which the potentially sensitised person will NOT from antibodies, hence if the anti-D is given within this time period the anti-D will destroy the foetal blood cells before the mother's immune system can respond and form a memory. Potentially sensitising events include: spontaneous or intended abortion, placental abruption, small unnoticed placental bleeds, threatened miscarriage with or without observed bleeding, amniocentisis, ecv, birth, retained placenta, and similar events. Once a mother has been sensitised then that is it in the sense that future pregnancies will need to be monitored and antibody titres done to ensure the well being of the baby in the interests of preventing HDN if possible. There are many issues around anti-D not the least being that it is a blood product and thus a potential source of blood born contaminants/pathogens. I do believe to date the actual processing needed to produce these antibodies from sensitised donors has prevented the transmition of the blood born pathogens. Nevertheless the potential remains and we would be fools to ignore it, the scientific community certainly doesn't ignore it. Other issues have included the potential for these antibodies to cross the placenta and start destroying the baby's blood cells themselves. If this has happened I have not known it to be a significant issue: that is not the source of significant hemolysis or anaemia in neonates possibly because the supply is limited and not able to replicate itself. Another issue is the possibility for the antibodies to sensitise an Rh negative baby, again I don't think this has ever been recorded and to be honest doesn't make immunological sense to me but that doesn't mean it couldn't happen (I am not an immunologist). Anti-D has been given prophylactically in various communities around the world since the late 1960's and has been extremely effective in preventing HDN. As with all medications informed consent should be given. Have you visited Sara Wickham's site at http://www.withwoman.co.uk/. marilyn ----- Original Message ----- From: "Nicole Carver" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, October 25, 2004 2:40 AM Subject: [ozmidwifery] Re: > Hi Kristin, > I have concerns about the reasoning behind the giving of anti D in > pregnancy. It is apparently done because some women develop anti D > antibodies without any obvious clinical events that can be treated with anti > D when they occur. (Previously anti D was only given if there was an event > whereby foetal cells could enter the maternal circulation). I can't > understand how giving anti D twice in pregnancy can prevent antibody > formation for the whole pregnancy, when after birth, it must be given within > 72 hours to be effective. If the same period of action applies in pregnancy, > wouldn't it have to be given every three days throughout the pregnancy? > Perhaps someone can set me straight on this? The other thing I am concerned > about is the wide scale use of a blood product on pregnant women. I feel > certain that many women are not giving true informed consent to this. > Kind regards, > Nicole Carver. > > ----- Original Message ----- > From: "Kristin Beckedahl" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Monday, October 25, 2004 6:52 PM > > > > > > > > Dear List, > > > > I have recently heard of the Anti-D that can be given during pregnancy > > (28weeks?) for the prevention of HDN... does anyone know how effective it > > is, and if it is safe...? Thanks, Kristin > > > > > > -- > > This mailing list is sponsored by ACE Graphics. > > Visit <http://www.acegraphics.com.au> to subscribe or unsubscribe. > > > -- > This mailing list is sponsored by ACE Graphics. > Visit <http://www.acegraphics.com.au> to subscribe or unsubscribe. -- This mailing list is sponsored by ACE Graphics. Visit <http://www.acegraphics.com.au> to subscribe or unsubscribe.
