The Little Mermaid


One of the down side to being an obstetrician, is that things don’t always go well.  In general, I know many people think that my job is just about delivering babies, but that is such a small part of what I do.  I often help people through the most agonizing, life changing situations.  It makes me go home at the end of my day and hold my little ones close to me.

I once cared for a lady with a history of recurrent pregnancy loss.  She was investigated to the full extend of our current knowledge and no clear cause was identified.  She and her husband are not consanguineous and more than anything in the world, they want to have a baby.  They do not have trouble getting pregnant, but somewhere between 8-12 weeks, they have lost four babies.  Three had visible heart rates before the miscarriage.

This pregnancy was supposed to be different.  She was followed as closely as medically possible.  Early after pregnancy confirmation, her HCG’s were rising perfectly.  She was nauseated, but not too nauseous.  No spotting and no cramping.  Fetal pole and heart rate were seen at 8 weeks, and the crown-rump length showed appropriate growth at 11 weeks.  She was in the clear, or so we all thought.

Although she would never have terminated a baby affected by trisomy 21, she was interested in having integrated prenatal screening.  She went for her nuchal translucency scan, the the first sign of problems was noted.  There was essentially no amniotic fluid around the baby.

Although the fetal kidney’s start to function around 6-7 weeks of gestation, it is not until the second trimester that they are mainly responsible for the production of amniotic fluid.  After about 13-14 weeks, the absences of amniotic fluid is most often due to premature rupture of membranes or a severe defect in the renal-urinary system.  Any profound oligohydramnios, or as in this case, anhydramnios, carries a dismal prognosis for the baby.  This leads to the Potter’s Sequence, where the fetal lungs cannot use amniotic fluid to expand the future air pockets.  This leads to a lethal underdevelopment of the lungs call pulmonary hypoplasia.

Sometimes it can be difficult to determine the cause of a Potter’s sequence, but the diagnosis of the sequence itself is not difficult.  Prenatally, the actually cause may not be as important to determine prior to delivery, because it does not change the outcome for baby.  It is always bad.  Potter’s syndrome is a specific cause, which is caused by the absence of the fetal kidney’s.  Other causes include an obstructed bladder, where the urine never exits the bladder and there is no accumulation of amniotic fluid as a results.  The pressure in the urinary system often leads to renal dysfunction of destruction, so even if the bladder obstruction could be corrected, the damage is already done by the time we diagnosis the problem.  We can’t replace the fluid of the long term.  There are genetic renal conditions that lead to abnormal or absent renal development and or function.  There are a variety of structural problems that can lead to this outcome.

For this couple, the absence of fluid was devastating.  This have been their most normal pregnancy, and now this was a lethal malformation.  They were not prepared to just terminate, they wanted to gather some more information before saying good bye to this fetus.  It is very difficult to image a 13 week fetus without amniotic fluid.  Our views are limited by fetal position, and everything is very very small.  Even so, I was concerned that this fetus likely had bilateral renal agenesis, or absent kidneys.  This is often an isolated defect and can be sporadic, meaning there is not an underlying genetic or chromosomal abnormality.  However, I also had concerns about the heart of this baby.  From my limited observation, it appeared abnormal, potential a severe defect that in itself could be life threatening.

For this couple, they wanted to know there options.  Like most things, there are only some many choices, and none of them are really nice choices to make.  The first choice is they could continue the pregnancy.  They would likely deliver a baby at term who would die within minutes of birth.  There would also be a high risk of stillbirth due to the absent amniotic fluid and the risk for cord compression.  They would terminate the pregnancy straight-away, either by D&E or an induction.  If they wanted an autopsy, an induction of labour would provide an intact fetus to examine.  Not really a pleasant conversation to have with families.  The final choice would be to try and get a better look at the baby with an amnio-infusion.  This is a special time of amniocentesis where fluid is put in, instead of taking fluid out.  It allows a better look, and sometimes allows us make a more definitely diagnosis, thus allowing some women to choose a D&E because we have our answers.  It also helps identify the subset of patients with ruptured membranes, because we include a blue dye in the infusion, making it really easy to determine if they are leaking amniotic fluid.  Although it won’t necessarily change things for this pregnancy, it will provide valuable information for future pregnancies.

This couple decided to have the amnio-infusion, followed by a termination of pregnancy if renal agenesis and the suspected heart defect was confirmed.  The infusion was the first I had every performed, but it went well.  Once there was fluid around the baby, we asked her to go home, and we would do the scan the next day so that we could let the bubbles and turbulence settle.  Unfortunately she returned later that night with clear evidence of ruptured membranes.  I am sure that is was iatrogenic, because when the ultrasound was repeated, the baby clearly had no kidneys, and the heart was definitely abnormal.  She had an induction that night and delivered the next morning.

I was called to examine the fetus, because there was an unexpected finding.  The baby had fused legsIt had sirenomelia, or the mermaid syndrome.  This is a rare condition occurring in 1 in 100,000 pregnancies.  It is nearly uniformly lethal, and rare cases of prolonged survival are unusual in that they don’t have severe renal dysfunction and anhydramnios.  The urogenital organs do not develop properly and there is often no bladder or at least no bladder outlet.

It was heart breaking to hand this little mermaid over to her* parents.  Originally, they hadn’t wanted to see the baby, but after I described her to her parents, they wanted to hold her and say good-bye.


My daughter is a big fan of Disney’s The Little Mermaid.  She likes to pretend that she is a mermaid and tie her legs together.  However, now I often this of this couple and their little mermaid who will never grow up, and I wonder why like can be so unfair.  I am so lucky have my children, I hope they will be so lucky in the future too.

*Genetic testing was done to determine gender from the earlier amniocentesis

For more information on Potter’s Syndrome, please see:

Emedicine Review

Potter’s Syndrome Organization


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