Leading cause of premature baby

In humans, preterm birth refers to the birth of a baby of less than 37 weeks gestational age. Premature birth, commonly used as a synonym for preterm birth, refers to the birth of a premature infant. The child may commonly be referred to throughout their life as being born a "preemie" or "preemie baby". Because it is by far the most common cause of prematurity, preterm birth is the major cause of neonatal mortality in developed countries. Premature infants are at greater risk for short and long term complications, including disabilities and impediments in growth and mental development. Significant progress has been made in the care of premature infants, but not in reducing the prevalence of preterm birth.[1] The cause for preterm birth is in many situations elusive and unknown; many factors appear to be associated with the development of preterm birth, making the reduction of preterm birth a challenging proposition.
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Classification

Pregnant mother's body weakness and fatigue resulting overall long travel, or daily commuting from the duty station to the center housing, especially if such a distance away.
In that they continue developing after birth, most animals are not born mature. At birth, a normal human infant is less mature than infants of some other primate species, possibly to allow the disproportionately large head to fit through a pelvis adapted for walking on two legs.

In humans, whereas the usual definition of preterm birth is birth before 37 weeks gestation,[2] a "premature" infant is one that has not yet reached the level of fetal development that generally allows life outside the womb. In the normal human fetus, several organ systems mature between 34 and 37 weeks, and the fetus reaches adequate maturity by the end of this period. One of the main organs greatly affected by premature birth is the lungs. The lungs are one of the last organs to develop in the womb; because of this, premature babies typically spend the first days/weeks of their life on a ventilator. Therefore, a significant overlap exists between preterm birth and prematurity: generally, preterm babies are premature and term babies are mature. Prematurity can be reduced to a small extent by using drugs to accelerate maturation of the fetus, and to a greater extent by preventing preterm birth.
  Leading cause of premature baby

Signs and symptoms

Symptoms of imminent spontaneous preterm birth are signs of premature labor; such signs consists of four or more uterine contractions in one hour before 37 weeks' gestation. In contrast to false labor, true labor is accompanied by cervical shortening and effacement. Also, vaginal bleeding in the third trimester, heavy pressure in the pelvis, or abdominal or back pain could be indicators that a preterm birth is about to occur. A watery discharge from the vagina may indicate premature rupture of the membranes that surround the baby. While the rupture of the membranes may not be followed by labor, usually delivery is indicated as infection (chorioamnionitis) is a real threat to both fetus and mother. In some cases the cervix dilates prematurely without pain or perceived contractions, so that the mother may not have warning signs until very late in the birthing process.

Mortality and morbidity

The shorter the term of pregnancy, the greater the risks of mortality and morbidity for the baby primarily due to the related prematurity. Preterm-premature babies ("preemies" or "premies") have an increased risk of death in the first year of life (infant mortality), with most of that occurring in the first month of life (neonatal mortality). Worldwide, prematurity accounts for 10% of neonatal mortality, or around 500,000 deaths per year.[3] In the U.S. where many infections and other causes of neonatal death have been markedly reduced, prematurity is the leading cause of neonatal mortality at 25%.[4] Prematurely born infants are also at greater risk for having subsequent serious chronic health problems as discussed below.

The earliest gestational age at which the infant has at least a 50% chance of survival is referred to as the limit of viability. As NICU care has improved over the last 40 years, viability has reduced to approximately 24 weeks,[5][6] although rare survivors have been documented as early as 21 weeks.[1] This date is controversial as gestation in this case was measured from the date of conception rather than the date of her mother's last menstrual period. Gestation appears 2 weeks less than if calculated by the more common method.[7] As risk of brain damage and developmental delay is significant at that threshold even if the infant survives, there are ethical controversies over the aggressiveness of the care rendered to such infants. The limit of viability has also become a factor in the abortion debate.

Specific risks for the preterm neonate

 Preterm infants usually show physical signs of prematurity in reverse proportion to the gestational age. As a result they are at risk for numerous medical problems affecting different organ systems.

    * Neurological problems include apnea of prematurity, hypoxic-ischemic encephalopathy (HIE), retinopathy of prematurity (ROP), developmental disability, cerebral palsy and intraventricular hemorrhage, the latter affecting 25 percent of babies born preterm, usually before 32 weeks of pregnancy.[8] Mild brain bleeds usually leave no or few lasting complications, but severe bleeds often result in brain damage or even death.[8]
    * Cardiovascular complications may arise from the failure of the ductus arteriosus to close after birth: patent ductus arteriosus (PDA).
    * Respiratory problems are common, specifically the respiratory distress syndrome (RDS or IRDS) (previously called hyaline membrane disease). Another problem can be chronic lung disease (previously called bronchopulmonary dysplasia or BPD).
    * Gastrointestinal and metabolic issues can arise from hypoglycemia, feeding difficulties, rickets of prematurity, hypocalcemia, inguinal hernia, and necrotizing enterocolitis (NEC).
    * Hematologic complications include anemia of prematurity, thrombocytopenia, and hyperbilirubinemia (jaundice) that can lead to kernicterus.
    * Infectious include sepsis, pneumonia, and urinary tract infection

Causes

 As the cause of labor still remains elusive, the exact cause of preterm birth is also unsolved. Labor is a complex process involving many factors. Four different pathways have been identified that can result in preterm birth and have considerable evidence: precocious fetal endocrine activation, uterine overdistension, decidual bleeding, and intrauterine inflammation/infection.[9] Activation of one or more of these the these pathways may have been gradually over weeks, even months.[9] From a practical point a number of factors have been identified that are associated with preterm birth, however, an association does not establish causality.

Maternal background

A number of factors have been identified that are linked to a higher risk of a preterm birth: low socio-economic or educational standing and single motherhood,[1] as well as age at the upper and lower end of the reproductive years be it more than 35[10] or less than 18 years of age.[1] Further, in the US and the UK Afro-American and Afro-Caribbean women have preterm birth rates of 15–18% more than double than that of the white population. This discrepancy is not seen in comparison to Asian or Hispanic immigrants and remains unexplained.[1]

Pregnancy interval makes a difference as women with a 6 months span or less between pregnancies have a two-fold increase in preterm birth.[11] Studies on type of work and physical activity have given conflicting results, but it is opined that stressful conditions, hard labor, and long hours are probably linked to preterm birth.[1] Patients who had undergone previous induced abortions have been shown to have a higher risk of preterm birth only if the termination was performed surgically but not medically.[12] Adequate maternal nutrition is important. Women with a low BMI are at increased risk for preterm birth.[13] Further, women with poor nutritional status may also be deficient in vitamins and minerals. Adequate nutrition is critical for fetal development and a diet low in saturated fat and cholesterol may help reduce the risk of a preterm delivery.[14] Obesity does not directly lead to preterm birth; however, it is associated with diabetes and hypertension which are risk factors by themselves.[1] Women with a previous preterm birth are at higher risk for a recurrence at a rate of 15–50% depending on number of previous events and their timing.[15] To some degree those individuals may have underlying conditions (i.e. uterine malformation, hypertension, diabetes) that persist. Genetic make-up is a factor in the causality of preterm birth. An intra- and transgenerational increase in the risk of preterm delivery has been demonstrated.[16][17] No single gene has been identified, and it appears with the complexity of the labor initiation, that numerous polymorphic genetic interactions are possible.

Factors during pregnancy

Multiple pregnancies (twins, triplets, etc.) are a significant factor in preterm birth. The March of Dimes Multicenter Prematurity and Prevention Study found that 54% of twins were delivered preterm vs. 9.6% of singleton births.[18] Triplets and more are even more endangered. The use of fertility medication that stimulates the ovary to release multiple eggs and of IVF with embryo transfer of multiple embryos has been implicated as an important factor in preterm birth. Maternal medical conditions increase the risk of preterm birth, and often labor has to be induced for medical reasons; such conditions include high blood pressure,[19] pre-eclampsia,[20] maternal diabetes,[21] asthma, thyroid disease, and heart disease. In a number of women anatomical issues prevent that the baby is carried to term. Some women have a weak or short cervix[19] (the strongest predictor of premature birth)[22][23][24] The cervix may also have been compromised by previous cervical conization or loop excision. In women with uterine malformations the capacity of the uterus to hold the growing pregnancy may be limited and preterm labor ensues.[25] Women with vaginal bleeding during pregnancy are at higher risk for preterm birth. While bleeding in the third trimester may be a sign of placenta previa or placental abruption – conditions that occur frequently preterm – even earlier bleeding that is not caused by these two conditions is linked to a higher preterm birth rate.[26] Women with abnormal amounts of amniotic fluid, too much (polyhydramnios) or too little (oligohydramnios) are also at risk.[1] The mental status of the women is of significance. Anxiety[27] and depression have been linked to preterm birth.[1] Finally, the use of tobacco, cocaine, and excessive alcohol during pregnancy also increases the chance of preterm delivery. Tobacco is the most commonly abused drug during pregnancy and also contributes significantly to low birth weight delivery.[28][29] Babies with birth defects are at higher risk of being born preterm.[30]
[edit] Infection

Infection

 Infections play a major role in the genesis of preterm birth and may account for 25–40% of events.[31] The frequency of infection in preterm birth is inversely related to the gestational age.[1] Endotoxins released by microorganisms and cytokines stimulate deciduasl responses including the release of prostaglandins which may stimulate uterine contractions. Further the decidual response may include release of matrix-degrading enzymes that weaken fetal membranes leading to premature rupture.[31] Intrauterine infection appears to be a chronic process.[31] Typical organisms identified in the uterus before rupture of the membranes are genital Mycoplasma spp and specifically Ureaplasma urealyticum. Micro-organisms may reach the decidua in a number of ways, ascending, hematogeneous, iatrogenic by a procedure, or retrograde through the fallopian tubes. From the deciduas they may reach the space between the amnion and chorion, the amniotic fluid, and finally the fetus. A chorioamnionitis also may lead to sepsis of the mother. Fetal infection not only is linked to preterm birth but to significant long-term handicap including cerebral palsy.[1] It has been reported that asymptomatic colonization of the decidua occurs in up to 70% of women at term using a DNA probe suggesting that the presence of micro-organism alone may be insufficient to initiate the infectious response. Bacterial vaginosis has been linked to preterm birth raising the risk by a factor of 1.5 – 3.[32] As the condition is more prevalent in black women in the US and the UK, it has been suggested to be an explanation for the higher rate of preterm birth in this population. It is opined that bacterial vaginosis before or during pregnancy may affect the decidual inflammatory response that leads to preterm birth.[1] A number of maternal bacterial infections are associated with preterm birth including pyelonephritis, asymptomatic bacteriuria, pneumonia, and appendicitis. Also periodontal disease has been shown repeatedly to be linked to preterm birth.[33] In contrast, viral infections, unless accompanied by a significant febrile response, are considered not to be a major factor in relation to preterm birth.
 

Diagnosis

Helpful clinical test should predict a high risk for preterm birth during the early and middle part of the third trimester, when their impact is significant. Many women experience false labor (not leading to cervical shortening and effacement) and are falsely labelled to be in preterm labor. The study of preterm birth has been hampered by the difficulty in distinguishing between "true" preterm labor and false labor.[9] These new test are used to identify women at risk for preterm birth.

Fetal fibronectin                                                                                                                                      

 Fetal fibronectin has become the most important biomarker—the presence of this glycoprotein in the cervical or vaginal secretions indicates that the border between the chorion and deciduas has been disrupted. A positive test indicates an increased risk of preterm birth, and a negative test has a high predictive value. It has been shown that only 1% of women in questionable cases of preterm labor delivered within the next week when the test was negative

Ultrasonography of the cervix

Obstetric ultrasound has become useful in the assessment of the cervix in women at risk for premature delivery. A short cervix preterm is undesirable: At 24 weeks gestation a cervix length of less than 25 mm defines a risk group for preterm birth. Further, the shorter the cervix the greater the risk.[35] It also has been helpful to use ultrasonography in women with preterm contractions, as those whose cervix length exceeds 30 mm are unlikely to deliver within the next week

Prevention

Historically efforts have been primarily aimed to improve survival and health of preterm infants (tertiary intervention). Such efforts, however, have not reduced the incidence of preterm birth. Increasingly primary interventions that are directed at all women, and secondary intervention that reduce existing risks are looked upon as measures that need to be developed and implemented to prevent the health problems of premature infants and children. 

Primary (aimed at all women)

 The prevention of premature births is what needs to be focused on today. That is what the professionals in the health care community are struggling with. “Reasons for this include a lack of universal access to health care for women of childbearing age or pregnant women of any age”. Depression is a leading cause for premature births. Women suffering with this disorder need to make sure they are in continuous treatment in order for their symptoms to be controlled and monitored. Becoming overly stressed and upset can trigger premature labor in an otherwise healthy woman.There needs to be more focus on the decisions pregnant women make and the potential effects on their unborn child, including smoking, drugs, and alcohol. Partaking in any of these activities first and foremost denies the fetus from proper nourishment. Smoking increases the risk of premature births and possibly stillbirths. Abusing alcohol while pregnant has been linked to children with behavioral problems later in life, as well as fetal alcohol syndrome. Illegal drugs attribute to birth defects and premature births. All of the above should be enough for a woman to make better lifestyle changes while she is caring a child, but unfortunately it is not made public enough.

Other than the lifestyle choices an expecting mother can make, there are some cases that a premature birth is not in the mother’s hands. Of all premature births, 40 percent do not have a known cause. There are though four main routes that can lead to a premature birth or spontaneous premature labor. Infections is the first of these four. Usually urinary tract infections or infections involving the genitals can trigger a woman to go into preterm labor. Fetal and maternal stress is the second of the four. CRH, corticotrophin-releasing hormone, which is produced when the mother and or fetus are under unusual stress can cause other hormones to be released which can trigger uterine contractions, resulting in a premature birth.

Placental abruption is the third and can cause bleeding. Multiple births or an abundance of amniotic fluid may cause the uterus to stretch which is the fourth route that is identified in the causes of premature births. This can also lead to chemicals being released that cause uterine contractions. Scientists are and have been working on interventions to prevent premature births, but there is not one final answer to prevent all children from being born prematurely.

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