Bay Area Urology
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  Prenatal Diagnosis

What is prenatal diagnosis?

It can be defined as the detection of a structural, chromosomal or genetic fetal condition before delivery.

What are its goals?

Its ultimate goal is to offer parents options for treatment and pregnancy management. It may simply alter the timing, mode or site of delivery. In more complex cases early diagnosis might lead to consideration of fetal intervention or early postnatal (post delivery) management of the detected abnormality.

What tools are available for prenatal diagnosis?

The tools include a detailed family history, maternal (mother) serum screening, karyotype (chromosome) analysis, and ultrasound (or sonography).

What is an ultrasound study?

Ultrasound is an imaging technique using ultrasound waves. Its attractiveness includes lack of radiation exposure and being non-invasive. Nearly 75% of pregnant women undergo examination primarily related to high patient expectations and demand. Despite widespread use, there has never been a well-designed study clearly showing improved maternal or fetal outcomes in screened populations.

What urological abnormalities are detected by ultrasound?

The major urological abnormalities identifiable by ultrasound include kidney defects (e.g. hydronephrosis), bladder defects (e.g. urine reflux, exstrophy = literally means turned inside out, and prune-belly syndrome), urethral obstruction (e.g. urethral valves in boys), and defects of the spine and spinal cord (e.g. myelomeningocele). The most common prenatally-identified abnormality is hydronephrosis.

What can be done when major abnormalities are identified?

When major abnormalities are identified in utero intervention and pregnancy termination are options available early in pregnancy. Unfortunately, based on some data it would appear that ultrasound detection of major urological abnormalities substantially increases the chance of pregnancy termination. It is concerning that some of these decisions are reached even with conditions that may not be life-threatening (e.g. bladder exstrophy).

What is in utero intervention?

This is medical and/or surgical treatment performed during pregnancy on the fetus, attempting to correct or provide a temporary solution to the underlying problem. These treatments are available at medical centers (usually university medical centers) with exclusive pediatric specialization. In the 1980s and 1990s, there was a great deal of interest in fetal intervention for urinary tract obstruction. The outcome of these series, however, was disappointing showing very little improvement in urological outcome, mainly due to inherent poor kidney function in these infants. Consequently, intervention is potentially beneficial only to a small percentage of fetuses with obstructive problems but reasonable kidney function.

What has been the real benefit of prenatal diagnosis?

A real benefit of prenatal diagnosis is decreased infectious complications. Historically, hydronephrosis and urine reflux (vesicoureteral reflux) present with infection or pain. Newborns with these prenatally-detected conditions are started on antibiotic prophylaxis. The subsequent incidence of infection in these children is small. With the low incidence of infections, infant morbidity has decreased and the indications for surgical intervention have changed. It has allowed urologists to understand and sometimes predict the natural course of an anatomical abnormality in an asymptomatic (without symptoms) patient. The indication for surgical intervention in a newborn with urethral obstruction (such as posterior urethral valves) are clear, but the indications for intervention in a newborn with a partially obstructed ureter with 35% kidney function are more debatable.

What do we now know about certain disease processes?

1. We now know that 15% to 20% of children with a history of prenatally-detected hydronephrosis have urine reflux that is frequently associated with developmental kidney scars. 2. We know that spontaneous resolution can occur in newborn males with grade 5 (highest) urine reflux. However, we do not know if detection of this reflux is important since most is low-grade and resolves with medical management.

*  This information is not intended to substitute for a consultation with a urologist. It is offered to educate patients on the basis of urological conditions in order to get the most out of their office visits and consultations. Please see our web page disclaimer for addition information.


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