I spent the day on the pediatric ward (on call) today. It wasn't a very busy day, thankfully, and I was able to spend some time with a little three-year-old (I'll call him John) with cerebral palsy (CP). This little fellow was in hospital for treatment of his rather severe constipation, a relatively benign complication of his complicated medical situation.
John was a cute little boy with bright brown eyes which smiled by themselves. His arms and legs wouldn't quite do what he wanted them to, always overshooting his carefully calculated attempts to grasp things, but they were his own. His perfect little ears fit nicely on each side of his head, nicely suited to frame his small face, even though he is deaf.
He was born at 25 weeks gestation, 15 weeks (almost 4 months) premature. His neonatal pediatricians had predicted he would never make it home alive. His developmental pediatrician, when he did go home, had said he would never walk, talk, think or laugh. His mother, 19 years old, had never laid eyes on him since her C-section. For months he languished, all alone, in a hospital crib in a standard North American tertiary care center. Such things were only supposed to happen in Russia or Romania... When the Children's Services finally took notice, he had been neglected for seven months. Sure, John got his feeds, he had good nursing care from both good nurses and bad, and he was resucitated when he stopped breathing, so he couldn't complain... except he was a little infant, growing up all alone in a hospital bed, in a body that couldn't do what he told it to.
This retrospective scenario becomes more striking when you find out that, at three years of age, little John knows over 200 signs. His new parents, who've had him for more than two years, are delighted to tell everyone about his subtle mood changes, his love for iceskating and how he pulled down the Christmas tree last year. It's quite a sight to see him snuggle close to his mom and eat his pureed diet, and how carefully he tries to touch his little light-up toys.
His adoptive mother's only regret is that she missed being with him for the first seven months of his life. "There's so much time that we can never get back," she says. "He could have had so much more..."
She wouldn't give him up "for all the tea in China."
I guess the moral of little John's story is that every outcome prediction isn't right, that we have every right to hope, and that every drop of love counts.
Sunday, November 13, 2005
Tuesday, November 08, 2005
Prenatal Diagnosis: some details
Just briefly, here are some of the details about prenatal screening and diagnosis...
Maternal Serum Screen
Also known as the Triple Screen, this 2nd Trimester maternal blood test looks at levels of alpha-fetoprotein (AFP), betaHCG, and unconjugated estriol (uE3) in maternal serum. Some centers also look at inhibin level and pregnancy associated plasma protein A (PAPP-A). (They can also check some of these levels in the first trimester, and integrate the results with the Triple Screen.) The first important point is that these tests are not diagnostic tests. They simply try to quantify the statistical likelihood or risk that the baby has one of three disorders: Down Syndrome (Trisomy 21), Edward's Syndrome (Trisomy 18) and open neural tube defects like spina bifida.
It is important to realize that this test, while posing no physical risk to the mother, does not get her any closer to knowing whether or not her baby has one of those three disorders. In fact, using the 2nd Trimester maternal serum screen by itself for Down Syndrome, the false positive rate is about 7%. If you screened 1000 women, 70 will have a "positive test" and only one baby will have Down Syndrome. (There are also, of course, false negatives.) The very real risk, here, is that 69 women will have tremendous psychological stress and worry for no reason. Many of them will move on to have amniocentesis for no reason. Amniocentesis carries a 1 in 200 risk of miscarriage, among other less common risks.
Other tests in what's called the IPS of integrated prenatal screen include 1st trimester serum levels (mentioned above) and a Nuchal Translucency (NT) ultrasound. The NT is done in week 11, 12 or 13, and measures the thickness of the fold at the back of the developing baby's neck, which is correlated with an increased risk of Down Syndrome. This is not a diagnostic test either. In combination with the serum tests it can help lower the overall false positive rate.
Amniocentesis and chorionic villus sampling (CVS) are actual diagnostic tests. A long needle is placed through the abdomen to sample the amniotic fluid or the chorion. Cells from the fluid can be analyzed to determine the baby's sex and presence of all sorts of genetic abnormalities. (The price goes up for each abnormality tested for). After one of these tests one can have a fair degree of certainty as to the presence or absence of a genetic or chromosomal disorder. Amnio has a 1/200, and CVS a 1/100 risk of miscarraige.
On the other hand, a routine ultrasound to check baby's anatomy at around 18 weeks can pick up an open neural tube defect in most cases.
Can you do anything about these disorders? Certainly not Down's or Edward's - no cure for these. For isolated menigomyelocele, a type of open NTD, there is promising research underway showing that intrauterine surgery, between weeks 24 and 30, can be of some benefit when compared to postnatal surgery. However, there are a lot of risks attached to surgery in utero (death being one of them), so that this surgery is not offered routinely.
The conclusion is that a routine 18 week ultrasound for anatomy will pick up many abnormalities in a baby (open NTDs, polycystic kidney disease, gastroscicis, etc.). Surgery, in the future, may be a routine option for some of these, but not really at the moment. As far as I can see, there is no reason to increase stress and worry with a Maternal Serum Screen if you are not going to abort the baby or risk miscarraige from amniocentesis or CVS.
Ultrasound
As far as the safety of ultrasound goes, I know of two large, randomized controlled trials, that demonstrate the safety of ultrasound in pregnancy. Keiler et al, in BJOG, 1997, looked at 4637 randomized pregnancies and found no reduced hearing, no reduced vision, and no difference in height/weight at ages 1, 4 and 7. Ultrasounds have been around for almost two generations, and there has yet to be a study showing detrimental effect. On the other hand, as Leivo et al. showed in a study of 9310 women, perinatal deaths were reduced in the ultrasound group (deaths around the time of delivery). It is a safe and cost-effective means to be reassured about the health of the baby instead of rushing of to a C-Section. It's also been shown to significantly increase parental bonding, as well as objectively reducing pregnancy-related anxiety levels.
Maternal Serum Screen
Also known as the Triple Screen, this 2nd Trimester maternal blood test looks at levels of alpha-fetoprotein (AFP), betaHCG, and unconjugated estriol (uE3) in maternal serum. Some centers also look at inhibin level and pregnancy associated plasma protein A (PAPP-A). (They can also check some of these levels in the first trimester, and integrate the results with the Triple Screen.) The first important point is that these tests are not diagnostic tests. They simply try to quantify the statistical likelihood or risk that the baby has one of three disorders: Down Syndrome (Trisomy 21), Edward's Syndrome (Trisomy 18) and open neural tube defects like spina bifida.
It is important to realize that this test, while posing no physical risk to the mother, does not get her any closer to knowing whether or not her baby has one of those three disorders. In fact, using the 2nd Trimester maternal serum screen by itself for Down Syndrome, the false positive rate is about 7%. If you screened 1000 women, 70 will have a "positive test" and only one baby will have Down Syndrome. (There are also, of course, false negatives.) The very real risk, here, is that 69 women will have tremendous psychological stress and worry for no reason. Many of them will move on to have amniocentesis for no reason. Amniocentesis carries a 1 in 200 risk of miscarriage, among other less common risks.
Other tests in what's called the IPS of integrated prenatal screen include 1st trimester serum levels (mentioned above) and a Nuchal Translucency (NT) ultrasound. The NT is done in week 11, 12 or 13, and measures the thickness of the fold at the back of the developing baby's neck, which is correlated with an increased risk of Down Syndrome. This is not a diagnostic test either. In combination with the serum tests it can help lower the overall false positive rate.
Amniocentesis and chorionic villus sampling (CVS) are actual diagnostic tests. A long needle is placed through the abdomen to sample the amniotic fluid or the chorion. Cells from the fluid can be analyzed to determine the baby's sex and presence of all sorts of genetic abnormalities. (The price goes up for each abnormality tested for). After one of these tests one can have a fair degree of certainty as to the presence or absence of a genetic or chromosomal disorder. Amnio has a 1/200, and CVS a 1/100 risk of miscarraige.
On the other hand, a routine ultrasound to check baby's anatomy at around 18 weeks can pick up an open neural tube defect in most cases.
Can you do anything about these disorders? Certainly not Down's or Edward's - no cure for these. For isolated menigomyelocele, a type of open NTD, there is promising research underway showing that intrauterine surgery, between weeks 24 and 30, can be of some benefit when compared to postnatal surgery. However, there are a lot of risks attached to surgery in utero (death being one of them), so that this surgery is not offered routinely.
The conclusion is that a routine 18 week ultrasound for anatomy will pick up many abnormalities in a baby (open NTDs, polycystic kidney disease, gastroscicis, etc.). Surgery, in the future, may be a routine option for some of these, but not really at the moment. As far as I can see, there is no reason to increase stress and worry with a Maternal Serum Screen if you are not going to abort the baby or risk miscarraige from amniocentesis or CVS.
Ultrasound
As far as the safety of ultrasound goes, I know of two large, randomized controlled trials, that demonstrate the safety of ultrasound in pregnancy. Keiler et al, in BJOG, 1997, looked at 4637 randomized pregnancies and found no reduced hearing, no reduced vision, and no difference in height/weight at ages 1, 4 and 7. Ultrasounds have been around for almost two generations, and there has yet to be a study showing detrimental effect. On the other hand, as Leivo et al. showed in a study of 9310 women, perinatal deaths were reduced in the ultrasound group (deaths around the time of delivery). It is a safe and cost-effective means to be reassured about the health of the baby instead of rushing of to a C-Section. It's also been shown to significantly increase parental bonding, as well as objectively reducing pregnancy-related anxiety levels.
