- Author: Jenny E Halfhill, DO; Chief Editor: Carl V Smith, MD more...
Ultrasound-guided needle placement is the standard for amnioreduction. Transplacental procedures should be avoided if possible.
A surgical site is created with appropriate skin scrubs and sterile towels. Sterile covers and sleeves should be available for the ultrasound transducer. Typically, the site chosen for amnioreduction is ventral to the fetus—that is, between the knees and the elbows. Before needle insertion, sonographic calipers may be used to calculate the approximate depth to which the needle should be advanced.
Current practice is to perform needle placement under direct ultrasonographic guidance, with the needle adjacent to the ultrasound transducer and sterile cover (see the image below). The needle is observed within the 2-dimensional image generated by the transducer as it moves into the target location.
Amnioreduction may be useful in singleton pregnancies complicated by polyhydramnios. If a substantial amount of fluid is to be removed, the reduction in the size of the uterus may be sufficient to change the anatomic orientation. As a preemptive measure in these circumstances, inserting the needle in a cephalic direction may be prudent. As drainage continues, the needle will then become caudally directed and thus will be less likely to disengage from the amniotic cavity.
If the pregnancy is viable, a nonstress test may be performed at the completion of amnioreduction to document fetal well-being. Testing may continue to be performed weekly or twice weekly thereafter, including biophysical profiles as appropriate, depending on the indication for the procedure. If the amnioreduction was performed for twin-twin transfusion syndrome (TTTS), additional amnioreduction procedures may be required.
In cases of mirror syndrome associated with TTTS, amnioreduction alone or with selective feticide may result in complications such as a transient exacerbation of anemia and hemodilution which may cause severe maternal complications.
In a Cochrane database meta-analysis of treatment interventions to improve maternal-fetal outcomes in TTTS, investigators found no difference between amnioreduction and endoscopic laser coagulation of anatomic vessels and between amnioreduction and septostomy in the following : overall death, death of at least one infant per pregnancy, or death of both infants per pregnancy. Between amnioreduction and septostomy, there was also no difference in gestational age at birth. Over the long term, although more surviving babies were neurologically intact at age 6 years in the laser group than in the amnioreduction groups, no significant difference was seen between the surviving babies alive at 6 years who had major neurologic abnormalities who were treated with these interventions (laser or amnioreduction).
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