Preterm Infant's impairments and complications

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According to World Health Organization (WHO) “Preterm birth is defined as babies born alive before 37 weeks of pregnancy are completed”. Every year an estimated 15 million babies are born premature, i.e. 1 in 10 babies and this number is rising with risk of neurodevelopmental and behavioural disabilities high in children and in adults who were born preterm. As more infants are surviving, the importance of finding ways to improve developmental outcomes and their quality of life becomes paramount.

Fig : Preterm Infant in NICU care

Categories of preterm birth Infant : 

A) Based on gestational age (GA): Normal gestational period is 38 weeks to 42 weeks

1. Extremely preterm infant : GA less than 28 weeks.
2. Very preterm infant : GA of 28 to 32 weeks.
3. Moderate to late preterm Infant : GA of 32 to 37 weeks

B) Based on birth weight : (Average birth weight of full term infant is 3500 g)

1. Low birth weight (LBW) : less than 2500 g
2. Very low birth weight (VLBW) : less than 1500 g
3. Extremely low birth weight (ELBW) : less than 1000 g

C) Based on weight for a specific gestational age :

1. Small for gestational age (SGA) : Weight less than 10th percentile
2. Appropriate for gestational age (AGA) : Weight 10 - 90th percentile
3. Large for gestational age (LGA) : Weight more than 90th percentile

Factors Associated with Preterm Birth ( According to centers of Disease control and prevention)

A) Social, Personal, and Economic Characteristics of mother :

• Low or high maternal age. 
• Black race. 
• Low maternal income or Socioeconomic status.

B) Medical and Pregnancy Conditions : 

• Infection. 
• Prior preterm birth. 
• Carrying more than 1 baby (twins, triplets, or more.) 
• High blood pressure during pregnancy.
• Diabetic mother

C) Lifestyle behaviour and habits :

• Tobacco and alcohol use. 
• Substance abuse. 
• Late prenatal care. 
• Stress.

Impairments found in Preterm infants :

1) Primitive reflexes are spinal cord and brain-stem level mediated reflexes which are involuntary, automatic in nature. In preterm, premature and neurologically affected infants these reflexes are not fully developed. These neonates may appear weak and hypotonic or may be hypertonic with abnormal or persistent primitive motoric responses.

2) Brain damage in neonates or infants associated with preterm birth may occur due to asphyxia, physical damage to brain (during birth), fetal intracranial hemorrhage, neonatal intraventricular hemorrhage, infection, preeclampsia. This leads to mild to severe cognitive and functional impairment, developmental delay, visual and auditory deficits. Infants may struggle to achieve age appropriate motor milestones. Brain damage may interfere with maturational process of CNS and this results in pathological release and persistence of abnormal tonic reflex activity. For example, in case of spastic or quadriplegic CP, the response may be increased and reflexes are retained for longer duration in life. The reflex will be more active on the affected side of upper-limb and lower-limb in spastic CP, whereas in athetoid or hypotonic CP the infants are weak, less active with decreased reflex response.

3) Some features of anatomical body part in preterm infant :

Ear cartilage :

• Preterm infant at 28 weeks of gestational age (GA) has a small amount of ear cartilage and/or flattened pinna.
• Preterm infant at 33 weeks of GA has increased ear cartilage, recoil and outer ridge of ear is curved inward.
• Term infant has well developed ear cartilage with instant recoil.

Fig : Ear cartilage on preterm and full term infant

Sole : 

• Preterm infant at 28 weeks of GA has flat sole with no prominent crease.
• Preterm infant at 33 weeks of GA has only an anterior crease on sole of the foot.
• Term infant has multiple crease on the sole.

Fig : Sole of preterm and full term infant

Breast tissue : 

• Preterm infant at 28 weeks of GA has no breast tissue and the areolae are barely visible.
• Preterm infant at 33 weeks of GA has breast tissue less than 1 cm and the areolae are raised and/or pigmented.
• Full term has clearly have a raised to a full areola with breast buds thay are 3 to 10 mm in diameter.

Fig : Breast tissue in preterm infant

Genitalia : On observation, full term infants have large genitalia as compared to preterm infants, who have smaller genitalia.

• In full term males infant, the testes are descended in the scrotum. Testes descend in scrotum at about 4 to 6 weeks before birth. Rugae (small elevation) visible on scrotum. Whereas preterm male infant, are at a risk of undescended testes with scrotum remaining flat and smooth after birth.
• In full term female infant, labia majora is larger than clitoris and labia minora. Whereas preterm female infant have prominent clitoris and labia minora, and smaller labia majora.

4) Feeding problems are common in preterm infants. These infants often appears to regress in feeding skills or might develop new feeding problems after hospital discharge. Premature infants may have weak or immature sucking ability due to preterm birth. Rooting and sucking reflex are not fully developed in preterm birth.

5) Preterm infants may not have been able to engage in normal pleasurable oral exploration because of motor structure and function immaturity or delay or intubation or lack of experience.

6) Premature or preterm infants with hypertonia may attend abnormal postures like backward arching or extended neck during inappropriate tactile stimulus while handling, during dressing, changing diapers or during feeds. The infants may be using neck extension to maintain airway flow for breathing. On the other hand, hypotonic infants have poor neck and trunk control leading to inability to sustain semi-flexed position during feeds. These abnormal postures causes difficulty to attain optimal feeding position.

7) Babies who are born near term (33–36 weeks of gestation) may not appear very different from term babies. They are now recognised to have other morbidities and outcomes, which are different from the term or more preterm babies. Preterm babies have less subcutaneous fat, are often oedematous and may have extensive lanugo, a larger head and large body surface area. Preterm or premature infants have less muscle bulk, poorly developed tendon and ligament structure as well as less body fat. Buccal fat pads are also not well developed. There is decreased opposition of tongue to the surface of oral cavity and reduced flexor tone with neck in extended position.

8) Transitional or disorganized feeding patterns are common in preterm or ill NICU infants learning to orally feeding. These infants have difficulty coordinating sucks and swallows with breathing. Problem in any one process or lack of coordination between process can have a profound effect of infant's feeding ability. Within pharynx, breathing and feeding shares a common space. This dual role of pharynx underlie the difficulties which is observed in premature infants when sucking, swallowing and breathing is not well coordinated during feeding process.

9) Preterm respiratory capacity : preterm or premature birth interrupts normal in-utero lung development, which results in significant alteration in lung function and physiology. Alveoli may form during saccular phase of human lung development (between 28 to 36 weeks of GA), but mature alveoli that are ready for function of gases exchange are fully developed in alveolar phase (36 weeks GA to term). During the alveolar phase, the epithelium and interstitium decrease in thickness, air-space walls proliferate, and the capillary network matures to its final single-capillary network. Blood-vessel development, which begins at the earliest stages, continues throughout lung development. Preterm or premature birth during this critical period may result in significant  alteration in lung function and physiology.

10) The skin in preterm infants is thin and fragile.  Transepidermal water loss also contributes towards excessive heat loss from the baby’s body. Therefore, high humidity should be maintained, if the baby is very premature till the baby’s skin is mature. Dehydration is known to result in electrolyte derangement, poor growth and temperature problems like dehydration fever. Incubator care is generally needed for more premature babies. In general, the lower the gestation, the higher is the incubator temperature. 

11) Preterm babies have limited reserves of glycogen, fat and gluconeogenesis, and are at high-risk of hypoglycaemia during first few days of life. In very preterm babies, insulin production is limited; this coupled with insulin resistance of the tissues may result in hyperglycaemia. Hyperglycaemia may produce osmotic diuresis, dehydration and electrolyte imbalance. 

12) Premature infants whose bone mineral requirements are different from full term newborns because calcium is deposited in foetus bone during the 3rd trimester. This calls for the need of dietary supplementation of vitamin D in premature neonates. There is evidence that hydroxylation of vitamin D in the liver of preterm infants is impaired and this together with dietary phosphate deficiency is an important factor in the osteopenia of preterm infants. 

13) Vitamin E deficiency except in the preterm infant is rare. In the preterm, vitamin E deficiency is occasionally associated with haemolytic anaemia and may contribute to the membrane damage associated with intraventricular haemorrhage and bronchopulmonary dysplasia. Newborn have a relatively low reserve of vitamin E because only small amounts of vitamin E cross the placenta. Thus, newborns, particularly preterm or premature infants are at increased risk of vitamin E deficiency.

14) The premature infant may have severe visual impairment caused by retinopathy of prematurity (ROP). All infants weighing less than 1500 g at birth or with a gestational age of 32 weeks or less should be screened for ROP by an ophthalmologist with experience in ROP screening until the blood vessels are mature, around 40 weeks from conception.

Complications associated with prematurity :

1) Respiratory Distress syndrome (RDS) : This condition is due to surfactant deficiency. Surfactant reduces the surface tension at the alveolar surface and prevents their collapse at the end of expiration. Babies of lower gestation have a higher risk of and severity of RDS. The clinical symptoms start soon after the birth and worsen gradually during first 6 hours of age. Signs and symptoms include increased work of breathing (intercostal and subcostal recession), grunting (exhalation against partially closed glottis to maintain functional residual volume) and cyanosis with increased oxygen requirement. Prophylactic surfactant has led to even extremely LBW babies been extubated within first 2 days of life. 

Fig : RDS in preterm infants

2) Hypothermia and hypoglycemia : It may be prevented through simple and inexpensive interventions. Risk factors for hypoglycaemia include birth asphyxia, prematurity and 

hypothermia. Hypothermia is common in developing countries, affecting more than half of all newborns in many communities, and is associated with an increased risk of mortality. Hypothermia also is associated with increased rates of morbidity, including increased risk of neonatal infections, coagulation defects, acidosis, delayed foetal-to-newborn circulatory adjustment, hyaline membrane disease and IVH. Effects of hypothermia on babies includes lethargy , poor feeding and weak cry, peripheral oedema, marked facial oedema (may give false impression of healthy infant). Hypothermia can be prevented by simple measures such as ensuring a warm environment during delivery, early breastfeeding and skin-to-skin contact with the mother, proper bathing, drying and swaddling, and prompt identification and rewarming of hypothermic neonates. 

3) Haemorrhagic and periventricular white matter brain injury : Intraventricular or periventricular haemorrhage (IVH) is a major problem in preterm babies born at less than 32 weeks of gestation. The more preterm the baby is, the higher the risk of IVH. Administration of antenatal steroids to the mother will reduce the risk. Risk of bleeding is highest during first 72 hours of life, slightly reduced from day 4 to 7. The risk of intraventricular bleed is low after day 7 of life. Although it is common practice to correct any clotting abnormality in preterm babies, there is lack of evidence on any reduction in the incidence of IVH. 

Like IVH, Periventricular Leukomalacia (PVL) is inversely related to gestational age. PVL is the most common ischemic injury to the preterm infant and results from lack of cerebral autoregulation leading to decreased blood flow in the vulnerable watershed arterial vessels. Subplate neurons, critical for normal neuronal organization and interaction, are destroyed in PVL, leading to decreased white matter. In addition, preoligodendrocytes are exquisitely sensitive to oxygen and glucose deprivation leading to markedly abnormal myelination.

Fig : Complications of brain in preterm and full-term infants

Fig : Brain complications in preterm and full-term infants

4) Bronchopulmonary dysplasia (BPD) : it is a distinct pulmonary disease affecting the developing lung after prolonged respirator or oxygen therapy in RDS. By giving oxygen under pressure ( through ventilator) can sometime hurt the air sacs in the lung. Also called chronic lung disease of prematurity, the radiological findings includes bubbly appearance of the lungs, hyperaeration and cardiomegaly. "Dysplasia" means abnormal changes in the structure or organization of a group of cells. The cell changes in BPD take place in smaller airways and lung alveoli, making breathing difficulty and causing problems with lung function.

5) Necrotising Enterocolitis : Necrotising enterocolitis is a severe disease of the GI tract. Prematurity or low birth weight is the most commonly associated factor and occurs in 90% of babies with this disease. Hypovolaemia and hypoxia result in damage within the mucosa cells initiating the NEC. Factors related to intestinal ischemia and inflammation, enteral feeing, and aberrant bacterial colonization (i.e. infection) have been shown to play a role in the development of NEC in premature infants. Thus, it is important to do assessments such as routinely measuring the abdominal girth of an infant, and assessing for pregavage residuals prior to gavage feeding. In addition, the inclusion of assessment of emesis, abdominal masses or tenderness, auscultation of bowel sounds in all four quadrants of the abdomen, and testing stool for occult blood are important.  Immediate medical management and intervention of bowel rest, gastric decompression, and introduction of antibiotic treatment is crucial to decreasing morbidity and mortality in these infant.

6) Apnoea/ anaemia of prematurity : Prolonged respiratory pauses (more than 20 seconds) in preterm infants may be associated with cyanosis and bradycardia. Although these may be related to immature respiratory centre particularly in babies born below 34 weeks of gestation (apnoea of prematurity), they may be a feature of underlying illness.

7) Persistent Patent Ductus Arteriosus : The ductus arteriosus serves an important function in the foetal life by diverting the blood from pulmonary trunk into aorta. It closes soon after birth as the pulmonary pressure falls. However, in preterm babies, it may not close due to immaturity of the ductal tissue. As the systemic pressure is higher than pulmonary pressure, the blood flows from aorta into pulmonary trunk and to lungs. This has important implications. Firstly, it increases the preload on the heart and secondly, it causes pulmonary congestion. The baby develops tachycardia, wide pulse pressure from diastolic run off and metabolic acidosis. Babies may develop renal dysfunction, reduced blood supply to gut (increased risk of necrotising enterocolitis) and arterial steal from the cerebral circulation. 

Fig : Patent Ductus Arteriosus in infants

Need for Early intervention :

After understanding about impairments and complications of preterm infant's birth, it becomes necessary for taking immediate actions to intervene these infants in terms of their medical management and rehabilitation. Early intervention is very important for their proper growth and development. 

During the first 1,000  days, the brain grows more quickly than at any other time in a person’s life and a baby needs the right nutrients at the right time to feed his/her brain’s rapid development. There are three crucial stages in the first 1,000 days: pregnancy, infancy and toddlerhood. 

It is rightly said that “A stitch in time saves nine"... it is better to fix a problem when it is small than to wait and let it become a bigger problem. Therefore, Early Intervention is crucial and important to timely invest on care of premature newborns in order to save them from being functionally impaired. The major purpose of early intervention is prevention of disability and developmental delay. Many research evidences concludes that early intervention programs  helps to improve cognitive outcomes as well as showed significant positive effect on motor development, social skills and adaptive response in infants.

You can also refer to our previous blogs related to preterm infant : (Click on the below link)

• NICU care : Neonatal feeding assessment
  
• Primitive Reflexes in infants and adults : Need to integrate primitive reflexes

Thankyou for reading!!!

Dr. Sheetal Tatar-Dhande, Dr. Pallavi Khadse-Kolhe, Dr. Ashwini Sangar.