Introduction and Overview
Thank you for joining us for today's webinar. If you were not able to attend last week's session, we discussed the many aspects of typical feeding development. As we concluded that course, I shared some of the things that can disrupt that progression. If you missed that live event, it is now available as a recorded course in SpeechPathology.com's library (Course ID: 8188).
During this course, and the three upcoming courses to follow, I'm going to share information about diagnoses and conditions that are associated with feeding problems. In this course, we will specifically address premature birth, the impact that it has on a child, as well as the related diagnoses and conditions that can develop as a result of prematurity. Hopefully, after this course, you'll have a deeper understanding and appreciation for what premature children and their families have experienced, which should have an impact on how you perform your tasks.
First, I'd like to list some specific populations that are at risk for premature births. These populations include:
- Women from low income households
- Women of color
- Women younger than 20; older than 40
- Women who were born premature
- Women with a history of a previous premature delivery
- Women with multiple pregnancies
- Women with uterine/cervical abnormalities
Additionally, the following risk factors also contribute to preterm births:
- Smoking, alcohol, substance use
- Unintended pregnancy
- Chronic health conditions
- In-vitro conception
- History of repeated miscarriages/spontaneous abortions
Incidence and Statistics
It is estimated that worldwide, an average of 11% of all births are premature. That translates to about 15 million preterm infants born per year. About 84% of those preterm infants are between 32 and 36 weeks estimated gestational age (EGA); 10% are between 28 and 32 weeks; and 5% of those infants are less than 28 weeks gestational age.
Premature birth is associated with approximately one-third of infant deaths in the United States. It accounts for 45% of children diagnosed with Cerebral Palsy, 35% of children with vision impairments, and 25% of children with cognitive and hearing problems.
Classification: Gestational Age and Birth Weight
Premature births are commonly classified as follows:
- Late preterm birth: An infant born between 34 and 36 weeks gestational age
- Very preterm birth: An infant born at less than 32 weeks gestational age
- Extremely preterm birth: An infant born at or below 28 weeks gestational age
As one may expect, there are more problems associated with infants who are born extremely preterm.
Another way to classify infants born prematurely is in terms of their birth weight.
- Low birth weight: less than 2500 grams (about five pounds)
- Very low birth weight: less than 1500 grams (about three pounds)
- Extremely low birth weight: less than 1000 grams
Unsurprisingly, there are many more negative outcomes associated with the extremely low birth weight.
It is important to note that the survival rate for premature births is improving. The Journal of the American Medical Association (JAMA) compared data from 1993 with data from 2012, and found survival rate increases at each gestational stage, as follows:
- 22 weeks: from 6% (1993) to 9% (2012)
- 23 weeks: from 28% (1993) to 33% (2012)
- 24 weeks: from 52% (1993) to 65% (2012)
- 25 weeks: from 68% (1993) to 81% (2012)
- 26 weeks: from 83% (1993) to 87% (2012)
- 27 weeks: from 84% (1993) to 94% (2012)
- 28 weeks: from 91% (1993) to 94% (2012)
Additionally, between 1990 and 2006, late preterm birth survival rates increased from 7.5% to 17.3%. Due to medical advancements, more infants can be saved; however, there are still many negative long- and short-term outcomes related to premature birth.
Adjusting for Prematurity
Adjusting for prematurity involves looking at the infant and accounting for how early they were born. The reason we adjust for prematurity is because infants who are born early are not as developed as infants who were carried full term. Premature babies still have to develop the same systems (e.g., nervous system, gastrointestinal system), but in a much less nurturing environment (i.e., outside the mother's womb). As such, we definitely want to "cut them some slack," typically until two to three years of age. Much of the literature supports adjusting for prematurity until the child reaches the age of three years.
In order to adjust for prematurity, we first determine the baby's gestational age in weeks. Then, subtract the gestational age from 40 weeks (full term) to find out how many weeks premature they were. Finally, look at the current chronological age of the child (the time at which they exited the womb), and subtract the weeks of prematurity, resulting in the weeks of adjustment.
For example, Baby Olivia was born at 30 weeks gestational age. If we subtract 30 weeks from 40 weeks, we can see that Olivia was 10 weeks premature. If Baby Olivia's current chronological age is 16 weeks, and she was 10 weeks premature, we need to adjust for 6 weeks of development.
Associated Diagnoses: Short-Term Complications
Some of the short-term complications associated with premature birth that we will cover today include, but are not limited to, the following:
- Respiratory complications
- Cardiovascular abnormalities
- Intraventricular hemorrhage (IVH)
- Necrotizing enterocolitis (NEC)
- Retinopathy of prematurity (RoP)
Hypothermia is a common problem in preemies. They don't have stored body fat like a full-term infant. They can't generate enough heat to counter what is lost through the surface of their bodies. They may have to use energy to stay warm, which takes away from the energy they need to grow. This can result in some metabolic disorders, because everything is immature. They can end up being hypoglycemic, which can typically be managed, but it's a problem when they're in the NICU. Hypothermia is also associated with increased mortality in preterm infants, along with intraventricular hemorrhage and pulmonary insufficiency.
Respiratory distress syndrome in premature infants occurs due to a lack of surfactant, which is a liquid that coats the lungs and helps them stay open rather than collapsing. A lot of these babies are born before surfactant has been produced. Artificial surfactant exists, but premature infants lack the surfactant that naturally occurs in full-term babies.
Infants with respiratory distress syndrome spend a long period of time on the ventilator, receiving high concentrations of oxygen, along with other interventions. Bronchopulmonary dysplasia (BPD) occurs as a result of all of those interventions, altering the normal lung development. It's similar to a chronic lung disease or chronic lung problem, which we will discuss in greater detail shortly.
Premature infants can also experience apnea of prematurity. Apnea is the cessation of breathing for 20 seconds or longer. In this world, it can be a shorter period of cessation of breathing if it's accompanied by bradycardia (when the heart beat drops below 60 beats per minute). Typically, if a baby is born before 28 weeks gestational age, episodes of apnea may take longer to cease, possibly extending beyond the period of term. If they're over 28 weeks, apnea will often be resolved by the time they reach what would have been their term, or their due date.
Although much research exists on this topic, I wanted to point to a few key studies that demonstrate the impact of respiratory diagnoses:
- Lin et al., 2017: The duration of this study was four years. Lin and colleagues looked at 83 preterm infants with BPD, 89 preterm infants without BPD and 98 healthy term infants. They found that the infants who had BPD had a much higher incidence of adverse neurodevelopmental outcomes at nine to 12 months, which was more than either of the other populations.
- Mizuno et al., 2007: Mizuno and colleagues looked at 20 different preterm infants of varying degrees of BPD. It was well documented that regardless of whether it was mild or severe BPD, all of the infants had feeding difficulties, which makes sense when you think about having to breathe and eat.
- Barlow, 2009: Barlow published an article supporting the fact that compared to healthy preterm infants without BPD, preterm infants with BPD have larger decreases in oxygen saturation and higher respiratory rates. As a result, they exhibited a lower performance on sucking measures. Again, this makes it difficult for babies trying to take a bottle or a breast.
In another course (Course ID: 8231), I discuss cardiovascular abnormalities in more detail. For the purposes of this course, I want to point out two abnormalities in particular. First, is patent ductus arteriosus (PDA). Before birth, the aorta and the pulmonary artery are connected by a blood vessel called the ductus arteriosus, which is essential for fetal blood circulation. That vessel is supposed to close after birth, often within minutes, but sometimes it takes a few days. In full-term infants, it typically closes successfully on its own, without intervention. However, preterm infants are notorious for having a PDA that remains open. It can be closed with medication, and if necessary, surgery. Additionally, due to immature vascular systems, premature infants tend to have systemic hypotension (low blood pressure).
In 2012, Laas and colleagues conducted a population-based study. They found that premature infants are two times as likely to have congenital heart defects (CHD) as term infants. Also, they found that preterm infants have a higher incidence of anomalies of ventricular outflow. One of those types of disorders is called transposition of the great arteries. If you remember your heart anatomy, the aorta is supposed to be on the left side, and the pulmonary artery is supposed to come from the right side. In someone with transposition of the great arteries, the aorta is on the right side and the pulmonary artery is coming from the left. Essentially, this means that oxygen rich blood from the aorta is not going out to the body; it just keeps going back for more oxygenation, which is not helpful. In addition, the pulmonary artery is sending blood out to the body that is not oxygenated, which again is not helpful. This condition needs to be surgically managed, and there are a number of different things that they do. One of the things they do is to keep the PDA open so that there's at least some mixing of the O2 rich blood with the non-O2 rich blood. In any case, you can appreciate how a disorder of this nature in a small infant could pose a real problem for feeding.
There are several studies that demonstrate the impact of prematurity on an infant's cardiovascular health:
- Sterken et al., 2016: This was a longitudinal study of 107 infants with congenital heart disease and 77 healthy infants. In a nutshell, when they looked at all of these infants as they turned age four, the ones with the heart problems had deficits in intelligence, visual motor integration, and psychosocial functioning. If you think about it, our visual system plays a huge part when we're learning and developing our eating skills (older infants learn to eat through observing other people). Also, our psychosocial system affects how we learn to eat, because eating is a relational activity that we partake in with other people.
- Mussatto et al., 2015: This article highlights that children with heart disease have a higher incidence of delays across the board. That's especially true when they have repeated heart surgery, longer hospital stays, and tube feedings.
- Massaro et al., 2008: This last study reiterates that children with CHD have an increased risk of neurodevelopmental impairments, although intelligence appears to be within normal limits.
Intraventricular Hemorrhage (IVH)
Intraventricular hemorrhage (IVH) is the most common neuropathological lesion of the preterm infant. It rarely occurs at birth. It typically occurs within the first three days of life. It occurs more frequently in infants born before 32 weeks estimated gestational age.
This is the grading system for IVH. We often think of grades one and two as likely to resolve, and not see a lot of problems; grades three and four can frequently carry with them severe problems that we can see long term.
- Grade I (Mild): Bleeding confined to germinal matrix
- Grade II (Moderate): IVH occupies 50 percent or less of lateral ventricle volume
- Grade III (Severe): IVH occupies more than 50 percent of lateral ventricle volume
- Grade IV (Severe): Hemorrhagic infarction in periventricular white matter ipsilateral to large IVH
Klebermass-Schrehof, et al. (2012) looked at data from 471 infants who passed through their NICU over an 11-year period. They found significantly lower psychomotor and mental scores in this population. There was an increased incidence of cerebral palsy (CP). They had poorer outcomes when the baby had IVH and was born before 28 weeks. They also found that even in children who had lower grades of IVH, as they grew, those children had poorer outcomes compared to healthy infants. Clearly, intraventricular hemorrhage impacts children significantly on multiple levels.
Necrotizing Enterocolitis (NEC)
The next short-term diagnosis is important, especially when we talk about feeding. Necrotizing enterocolitis (NEC) is one of the most common GI emergencies in a newborn. It occurs one in three per 1000 live births. It involves an ischemic necrosis of the intestinal mucosa. Essentially, oxygen is cut off and part of the bowel/intestine will die. The symptoms are extremely obnoxious. It can be resolved in seven to 10 days, but it can also result in lengthy hospital stays and surgeries.
Looking at these clinical characteristics, I think most of us would agree that if we were experiencing any of these symptoms, they would significantly impact our desire to eat. Infants who are experiencing NEC do not eat by mouth during that period until everything is resolved.
Systemic signs of NEC include:
- Respiratory failure
- Poor feeding
- Temperature instability
Abdominal signs of NEC include:
- Gastric retention
- Rectal Bleeding
- Bilious drainage
One of the complications/outcomes of NEC is short bowel syndrome (SBS), the incidence of which is 20 to 35% (Nino, Sodhi and Hackman, 2016). SBS is a malabsorption disorder caused by a lack of functional small intestine. Most cases are due to the surgical removal of a large portion of the small intestine. Many children with SBS had NEC as an infant. These children have a lifetime issues relating to feeding, metabolism and absorption.
The impact of necrotizing enterocolitis is highlighted in the following articles:
- Neu and Walker, 2011: Premature infants with NEC were hospitalized 60 days longer if surgery was required, and 20 days longer if no surgery was required, as compared to unaffected preterm infants.
- Rees et al., 2017: NEC was associated with worse neurodevelopmental outcomes than in preterm infants without the diagnosis. Advanced NEC with need for surgery increases the risk of neurological impairment. Approximately 50% of neonates with NEC have long-term neurodevelopmental problems.
- Shah et al., 2008: Infants with NEC are at greater risk for motor impairment.
All newborns should be eating, breathing, sleeping and becoming stronger. Unfortunately, newborns with NEC experience noxious stimuli which result in these negative outcomes, with the potential for ultimately ending up on our feeding caseload.
Infection and Sepsis
Another common complication associated with prematurity is late onset sepsis, which can occur after three days of life. It's associated with longer hospital stays. The complications that we've already talked about (e.g., BPD, PDA, NEC) are putting that child at greater risk for infection and sepsis.