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Our experience is that an amnio is essentially risk free. We prefer 12-13 weeks GA, but sometimes the need for an amnio is not identified until later. We use a "risk" factor of 1:1850 on our consent forms, for earl and later amnios, recognizing that other factors occuring at the time of an amnio, separate from the procedure can impinge on pregnancy outcome. |
As in all patient-physician relations, there is an implicit contract: the physician must always act in a way that he or she thinks is in the best interest of the patient and inform the patient thoroughly. Patients need to express their wishes, have uncertainties clarified and participate in care. We want patients to be comfortable and we want to be certain that there are no technical impediments to a safe procedure. If there is not a great tap site, we will not proceed. Needle placement is monitored by ultrasound - there is no uncertainty about needle passage or placement. We know a lot about this, because we invented the monitoring techniquein the mid 1970's that everyone uses now.
An basic part
of making an amnio very safe is precise selection of a tap site - a
near penpendicular path that avoids large blood
vessels in the wall of the
uterus,
the
umbilical
cord,
and, of course, the fetus. Early in pregnancy, the fetus is denser than amniotic fluid and rests at the bottom of the sac, leaving most of the fluid where it is accessible. Also, and most importantly, the muscle wall of the uterus is much less
vascular
11 to 13 weeks than
it is later, limiting the possibility of a uterine vessel injury during needle placement. |
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Our main concern with any percutaneous needle procedure is infection. We avoid infection by careful preparation of the skin entry site, meticulous sterile technique, and use of sterile, disposable products. We defer procedures, if there is a hint that the membranes may be infected - we assess this from fetal heart rate pattern and from tenderness of the uterus. The fetus is encased in a sticky, self repairing membrane called the amnion. The amnion seals itself instantly when the needle is withdrawn. There are no post procedure limitations of patient activity.
