
Newborns have unique and complex physiology that changes rapidly in the minutes, hours, days, and months after birth. Their appearance changes quickly in the first few days and weeks, and they exhibit a range of behaviours and characteristics that can be surprising to new parents. Many of these are normal, but some may indicate the need for medical attention. This article will explore the normal and abnormal characteristics of newborns, covering physical attributes, behaviours, and potential health concerns.
What You'll Learn
Skin rashes and jaundice
Skin Rashes
Most babies develop one or more skin rashes in their first week. Tiny white bumps on the chin and nose, known as milia, will disappear on their own. Many babies also develop a blotchy red rash called erythema toxicum, which fades within a few weeks. Stork bites and angel kisses are small, red "birth marks" on the eyelids and back of the neck. Salmon patches are caused by nests of blood vessels and usually fade within a few weeks or months.
Dry, peeling skin is common in newborns, especially those born a little late. The skin underneath is perfectly normal. Cradle cap (seborrhea) is another common skin condition that appears in the first few months of a baby's life. It causes greasy, yellowish crusts on the scalp and may include a red, irritating rash on the face, neck, and armpits.
Jaundice
Jaundice is a yellow discolouration of a newborn's skin and eyes, affecting nearly 50% of babies. It occurs due to a buildup of bilirubin, a yellow pigment from the breakdown of red blood cells, in the baby's blood. The liver normally removes this substance, but a newborn's immature liver may not be able to eliminate it quickly enough, leading to jaundice.
Jaundice typically appears two to four days after birth and usually goes away on its own within a couple of weeks. It is more common in breastfed babies and can last a month or longer. Treatment for jaundice is often not necessary, but in some cases, phototherapy or an exchange transfusion may be recommended.
While skin rashes and jaundice are typically harmless, it is important to monitor your baby's condition and seek medical advice if you have any concerns.
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Newborn behaviours
Sleeping
Newborns spend most of their time sleeping, even when being fed.
Crying
Newborns also grunt, grimace, squirm, kick, and startle easily.
Reflexes
Newborns have a Moro reflex, which is when they briefly stiffen their body in response to a noise. They also have a rooting reflex and a grasp reflex.
Breathing
Newborns breathe noisily and irregularly, particularly between three and six weeks old. Sneezing is how they clear their nose, and hiccoughs are frequent and harmless. Choking on mucus and milk and spitting up is very common in the first few days.section
Bowel Movements
Newborns often strain with bowel movements even when the stool is soft. Stools may vary in colour and consistency but are most often mustard yellow with a "cottage cheese" consistency.
Feeding
Newborns may have trouble feeding due to tongue movement being restricted by an anterior lingual frenulum.
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Genital characteristics
Ambiguous genitalia, also known as atypical genitalia, is a rare condition in which a newborn's external genitals are not clearly defined. The external genitals may not have developed completely, or they may have features of both sexes. This condition can be upsetting for parents and can have profound physical, social, and psychological effects on the child. The following sections will discuss the normal and abnormal characteristics of genitalia in newborns, focusing on the various types of ambiguous genitalia and their potential causes.
Normal Characteristics
In typical male and female development, the presence of the XY or XX chromosomes plays a pivotal role in determining the indifferent gonads. During the sixth week of gestation, these gonads develop into male-typical or female-typical gonads. The formation of typical male external genitalia is influenced by androgens, particularly dihydrotestosterone (DHT), which leads to the fusion of the urethral and labioscrotal folds, elongation of the genital tubercle, and the formation of the shaft of the penis. For typical female external genitalia, the absence of androgens is crucial to prevent virilization, resulting in the separation of the urethral folds and genital swellings to form the labia minora and majora, with the genital tubercle forming the clitoris.
Abnormal Characteristics
Ambiguous genitalia can arise from either an excessive or insufficient androgen effect on the neutral external genital anlage in males or females, respectively. The incidence of ambiguous genitalia in newborns is approximately one in 4,500. It is caused by hormonal irregularities during pregnancy, which interfere with the developing sex organs. The characteristics of ambiguous genitalia will depend on the sex chromosomes affected.
Characteristics in Genetic Females
- An enlarged clitoris that resembles a small penis.
- The urethral opening (where urine exits) may be in an atypical location.
- The "lips" of the vagina (labia) may fuse and resemble a scrotum.
- A lump of tissue within the labia that looks like a scrotum with testicles.
Characteristics in Genetic Males
- A penis that is absent or very small and resembles an enlarged clitoris.
- The urethral opening may be at the base of the penis instead of the tip.
- A small, separated scrotum that looks like labia.
- Undescended testicles.
Causes
The causes of ambiguous genitalia vary depending on the sex chromosomes present.
46 XX DSD
In this condition, the internal sex organs include ovaries and a uterus, but the external sex organs may resemble a penis and testicles. It is often caused by congenital adrenal hyperplasia (CAH), where the adrenal glands produce excessive amounts of androgens.
46 XY DSD
In this condition, the internal sex organs are male, but the external sex organs are unclear. It may be due to improper testicular development, insufficient testosterone production, or the body's inability to utilize testosterone effectively.
Disorders of Gonadal Differentiation
These disorders involve incomplete development of the sex organs, which may not fully develop into testes or ovaries.
Ovotesticular DSD
A rare condition where the sex organs have both ovarian and testicular tissue, or one ovary and one testis.
Diagnosis and Treatment
Most babies with ambiguous genitalia are diagnosed at birth, and a team of healthcare providers is often involved in determining the correct diagnosis and treatment plan. This team may include a paediatric endocrinologist, urologist, psychologist, and geneticist. Treatment options may include hormone replacement therapy and reconstructive surgery, with the goal of achieving normal-looking results and preserving sexual function and fertility.
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Eye characteristics
Normal Characteristics
Newborns' eyes are sensitive to bright light, so they are more likely to open their eyes in low light. It is normal for a newborn's eyes to sometimes cross or drift outward until their vision improves and eye muscles strengthen. This typically happens when they are falling asleep or being woken up. Newborns can also exhibit some degree of eyelid edema (puffiness) after birth, which makes it seem like they are having difficulty opening one or both eyes. However, this can be easily evaluated through a gentle examination, and the edema resolves over the first few days of life.
Abnormal Characteristics
Any abnormalities in the eyes should be carefully monitored and may require referral to an ophthalmologist or pediatrician.
Leukocoria
Leukocoria, or a white reflex, is an abnormal finding and may indicate the presence of cataracts, a tumor, or retinopathy of prematurity.
Cataracts
Cataracts can cause a reduced or absent red reflex and can lead to severe amblyopia if left untreated. They are most commonly caused by genetic mutations but can also be the result of chromosomal abnormalities, metabolic disorders, or congenital infection syndromes.
Glaucoma
A cornea size larger than 1 cm in diameter can be indicative of congenital glaucoma.
Retinopathy of Prematurity (ROP)
ROP is a major preventable cause of visual impairment that results from disordered retinal vascular development in preterm infants. It is classified into five categories, ranging from mild (stage I) to severe (stage V, denoting complete retinal detachment).
Retinoblastoma
Retinoblastoma is the most common neural retinal intraocular malignancy of childhood, accounting for 3% of all childhood cancers. It presents as a white reflex (leukocoria) instead of a normal red reflex or a complete absence of the red reflex, where the eye may appear black.
Nystagmus
Nystagmus is the repetitive, involuntary, to-and-fro oscillation of the eyes. It can be congenital or acquired and can be associated with various neurological and ocular abnormalities.
Strabismus
Strabismus, or a squint, is when the eyes do not look in the same direction. It can be caused by various factors such as congenital fibrosis of the extraocular muscles, Duane syndrome, or Möbius syndrome.
Aniridia
Aniridia is the hypoplasia or absence of the iris, usually affecting both eyes. It is associated with other ocular abnormalities, including cataracts, glaucoma, and corneal opacification, leading to reduced vision and nystagmus.
Congenital Ptosis
Congenital ptosis refers to the vertical narrowing of the eye opening due to drooping of the upper eyelid from birth. It can be caused by developmental dysgenesis of the levator palpebrae superiorus muscle or neurological conditions such as Horner's syndrome or oculomotor nerve palsy.
Other Abnormalities
Other potential eye abnormalities in newborns include entropion, epiblepharon, congenital dacryocystocele, microphthalmos, anophthalmos, coloboma, cryptophthalmos, and ankyloblepharon.
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Cardiovascular system
The cardiovascular system of a newborn is immature and distinct from that of an adult. The myocardium and autonomic control of the heart are underdeveloped, making newborns more susceptible to life-threatening haemodynamic changes.
Normal Characteristics
The cardiovascular system of a newborn is immature and distinct from that of an adult. The myocardium and autonomic control of the heart are underdeveloped, making newborns more susceptible to life-threatening haemodynamic changes.
The structure of the heart includes the atria, ventricles, and heart valves. Deoxygenated blood from the posterior and superior vena cava enters the right atria and ventricle during diastole and is pumped to the lungs via the pulmonary artery during systole. Oxygenated blood from the lungs returns to the left atria and ventricle via the pulmonary veins during diastole and is then pumped out to the body via the aorta during systole.
The heart rate of a newborn should be between 60 and 100 with a regular rhythm to be considered within the normal range.
Abnormal Characteristics
Abnormalities in the cardiovascular system of newborns can be congenital or acquired. Congenital abnormalities include atrial septal defects, ventricular septal defects, patent ductus arteriosus, transposition of the great vessels, coarctation of the aorta, and tetralogy of Fallot, among others. Acquired abnormalities can result from factors such as preterm birth, maternal diabetes, or environmental and genetic risk factors.
Some signs of cardiovascular abnormalities in newborns include chest pain, peripheral edema, unexplained sudden weight gain, shortness of breath, irregular pulse rate or rhythm, dizziness, or poor peripheral circulation.
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