INTRODUCTION:

Preterm birth, defined as childbirth occurring at less than 37 completed weeks or 259 days of gestation, is a major determinant of neonatal mortality and morbidity and has long-term adverse consequences for health. Children who are born prematurely have higher rates of cerebral palsy, sensory deficits, learning disabilities and respiratory illnesses compared with children born at term. The morbidity associated with preterm birth often extends to later life, resulting in enormous physical, psychological and economic costs¹.

The usual definition of preterm birth is birth before a gestational age of 37 complete weeks. 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 mature in the womb; because of this, many premature babies 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. Preterm babies born near 37 weeks often have no problems relating to prematurity if their lungs have developed adequate surfactant, which allows the lungs to remain expanded between breaths. Sequelae of 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 birth².

Meaning

Preterm birth (Latin: partus praetemporaneus or partus praematurus) is the birth of a baby of less than 37 weeks gestational age; such a baby is sometimes referred to as a "preemie" or "premmie", depending on local pronunciation².

Premature birth is defined either as the same as preterm birth or the birth of a baby before the developing organs are mature enough to allow normal postnatal survival².

Prevalence:

Significant progress has been made in the care of premature infants, but not in reducing the prevalence of preterm birth. Preterm birth is among the top causes of death in infants worldwide. Preterm birth rates have been reported to range from 5% to 7% of live births in some developed countries, but are estimated to be substantially higher in developing countries³.

Signs and Symptoms:

Preterm birth causes a range of problems. The main categories of causes of preterm birth are preterm labor induction and spontaneous preterm labor. Signs and symptoms of preterm labor include four or more uterine contractions in one hour. In contrast to false labor, true labor is accompanied by cervical dilatation 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 serious 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 process⁴.

Risk Factors:

As the cause of labor still remains elusive, the exact cause of preterm birth is also unsolved. In fact, the cause of 50% of preterm births is never determined. 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 over distension (placental abruption), decidual bleeding, and intrauterine inflammation/infection. Activation of one or more of these pathways may happen gradually over weeks, even months. From a practical point a number of factors have been identified that are associated with preterm birth; however, an association does not establish causality⁵.

Maternal Background:

· A number of factors have been identified that are linked to a higher risk of a preterm birth: age at the upper and lower end of the reproductive years, be it more than 35 or l ss than 18 years of age.⁶ Maternal height and weight can play a role.

· Pregnancy interval makes a difference as women with a six-month span or less between pregnancies have a two-fold increase in preterm birth. 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.⁶

· A history of spontaneous (i.e., miscarriage) or surgical abortion has been associated with a small increase in the risk of preterm birth, with an increased risk with increased number of abortions, although it is unclear whether the increase is caused by the abortion or by confounding risk factors (e.g., socioeconomic status). Pregnancies that are unwanted or unintended are also a risk factor for preterm birth.⁷

· Adequate maternal nutrition is important. Women with a low BMI are at increased risk for preterm birth. Further, women with poor nutrition 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.⁸Obesity does not directly lead to preterm birth; however, it is associated with diabetes and hypertension which are risk factors by themselves. 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. To some degree those individuals may have underlying conditions (i.e., uterine malformation, hypertension, diabetes) that persist.⁹

· 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. It appears with the complexity of the labor initiation that numerous polymorphic genetic interactions are possible.¹⁰

· Sub fertility is associated with preterm birth.

Factors during Pregnancy:

· Multiple pregnancies (twins, triplets, etc.) are a significant factor in preterm birth. 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. Often labor has to be induced for medical reasons; such conditions include high blood pressure, pre-eclampsia, maternal diabetes, asthma, thyroid disease, and heart disease.¹¹

· In a number of women anatomical issues prevent the baby from being carried to term. Some women have a weak or short cervix (the strongest predictor of premature birth) 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.¹²

· 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 conditions is linked to a higher preterm birth rate. Women with abnormal amounts of amniotic fluid, whether too much (polyhydramnios) or too little (oligohydramnios), are also at risk.

· The mental status of the women is of significance. Anxiety and depression have been linked to preterm birth.

· Finally, the use of tobacco, cocaine, and excessive alcohol during pregnancy increases the chance of preterm delivery. Passive smoking and/or smoking before the pregnancy influences the probability of a preterm birth.¹³

· Presence of anti-thyroid antibodies is associated with an increased risk preterm birth.⁶

Infection:

· Infections play a major role in the genesis of preterm birth and may account for 25–40% of events. The frequency of infection in preterm birth is inversely related to the gestational age.⁶

· Endotoxins released by microorganisms and cytokines stimulate deciduas 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. Intrauterine infection appears to be a chronic process.¹⁴ 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 the fetus. A chorioamnionitis also may lead to sepsis of the mother. Fetal infection is linked to preterm birth and to significant long-term handicap including cerebral palsy.⁶

Diagnosis

Many women experience false labor (not leading to cervical shortening and effacement) and are falsely labeled 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.These new tests are used to identify women at risk for preterm birth.⁵

Placental alpha microglobulin-1 (PAMG-1)

It has been the subject of several investigations evaluating its ability to predict imminent spontaneous preterm birth in women with signs, symptoms, or complaints suggestive of preterm labor.¹⁵ In one investigation comparing this test to fetal fibronectin testing and cervical length measurement via transvaginal ultrasound.

Fetal fibronectin has become an 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.⁶

Ultrasonography of the cervix

Obstetric ultrasound has become useful in the assessment of the cervix in women at risk for premature delivery. The shorter the cervix the greater the risk. 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.¹⁶

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.¹⁷

Before pregnancy

Adoption of specific professional policies can immediately reduce risk of preterm birth as the experience in assisted reproduction has shown when the numbers of embryos during embryo transfer were limited. Many countries have established specific programs to protect pregnant women from hazardous and night-shift work, and to provide them with time for prenatal visits and paid pregnancy-leave. Also, night work has been linked to preterm birth. Health policies that take these findings into account can be expected to reduce the rate of preterm birth.¹⁸ Avoidance of weight extremes and good nutritional support are important. Preconceptional intake of folic acid is recommended to reduce birth defects. There is significant evidence that long term (> one year) use of folic acid supplement preconceptionally may reduce premature birth. Reducing smoking is expected to benefit pregnant women and their offspring.¹⁸

During Pregnancy

Interventions that should have been initiated prior to pregnancy can still be instituted during pregnancy, including nutritional adjustments, use of vitamin supplements, and smoking cessation.

Screening of low risk women: Screening for asymptomatic bacteriuria followed by appropriate treatment reduces pyelonephritis and reduces the risk of preterm birth. Routine ultrasound examination of the length of the cervix identifies patients at risk.¹⁸

Self-care: Methods to reduce the risk of preterm birth include proper nutrition, avoiding stress, seeking appropriate medical care, avoiding infections, and the control of preterm birth risk factors (e.g. working long hours while standing on feet, carbon monoxide exposure, domestic abuse, and other factors). Self-monitoring vaginal pH followed by yogurt treatment or clindamycin treatment if the pH was too high all seem to be effective at reducing the risk of preterm birth.¹⁹

Secondary (Reducing Existing Risks):

Women are identified to be at increased risk for preterm birth on the basis of their past obstetrical history or the presence of known risk factors. Preconception intervention can be helpful in selected patients in a number of ways. Patients with certain uterine anomalies may have a surgical correction (i.e. removal of a uterine septum), and those with certain medical problems can be helped by optimizing medical therapies prior to conception, be it for asthma, diabetes, hypertension and others.

Reducing indicated preterm birth: A number of agents have been studied for secondary prevention of indicated preterm birth. Trials using low-dose aspirin, fish oil, vitamin C and E, and calcium to reduce preeclampsia demonstrated some reduction in preterm birth.¹⁸Reducing spontaneous preterm birth: Reduction in maternal activity – pelvic rest, limited work, bed rest – is frequently recommended although there is no clear proof of its efficacy. Use of nutritional supplements such as omega-3 polyunsaturated fatty acids is based on the observation that populations who have a high intake of such agents are at low risk for preterm birth, presumably as these agents inhibit production of proinflammatory cytokines.²⁰

Progesterone:

Progesterone, often given in the form of 17-hydroxyprogesterone caproate, relaxes the uterine musculature, maintains cervical length, and has anti-inflammatory properties, and thus exerts activities expected to be beneficial in reducing preterm birth. Progesterone supplementation also reduces the frequency of preterm birth in pregnancies where there is a short cervix.²¹

Cervical Cerclage:

In preparation for childbirth, the woman's cervix shortens. Preterm cervical shortening is linked to preterm birth and can be detected by Ultrasonography Cervical cerclage is a surgical intervention that places a suture around the cervix to prevent its shortening and widening. Instead of a prophylactic cerclage, women at risk can be monitored during pregnancy by sonography, and when shortening of the cervix is observed, the cerclage can be performed.¹⁸

COMPLICATIONS:

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 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. 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%.²²Prematurely born infants are also at greater risk for having subsequent serious chronic health problems as discussed below.

Short-Term Complications:

In the first weeks, the complications of premature birth may include:

· Breathing problems:

A premature baby may have trouble breathing due to an immature respiratory system. If the baby's lungs lack surfactant — a substance that allows the lungs to expand — he or she may develop respiratory distress syndrome because the lungs can't expand and contract normally. Preemies may also develop chronic lung disease known as bronchopulmonary dysplasia. In addition, some preemies experience prolonged pauses in their breathing, known as apnea.

· Heart problems:

The most common heart problems premature babies experience are patent ductus arteriosus (PDA) and low blood pressure (hypotension). While this heart defect often closes on its own, left untreated it can cause too much blood to flow through the heart and cause heart failure as well as other complications. Low blood pressure may require adjustments in intravenous fluids, medicines and sometimes blood transfusions.

· Brain problems:

The earlier a baby is born, the greater the risk of bleeding in the brain, known as an intraventricular hemorrhage. Most hemorrhages are mild and resolve with little short-term impact. But some babies may have larger brain bleeding which causes permanent brain injury.

Larger brain bleeds may lead to fluid accumulation in the brain (hydrocephalus) over a number of weeks. Some babies who develop hydrocephalus will require an operation to relieve the fluid accumulation.

· Temperature control problems:

Premature babies can lose body heat rapidly; they don't have the stored body fat of a full-term infant and they can't generate enough heat to counteract what's lost through the surface of their bodies. If body temperature dips too low, hypothermia can result. Hypothermia in a preemie can lead to breathing problems and low blood sugar levels. In addition, a preemie may use up all of the energy gained from feedings just to stay warm, not to grow bigger. That's why smaller preemies require additional heat from a warmer or an incubator until they're larger and able to maintain body temperature without assistance.

· Gastrointestinal problems:

Preemies are more likely to have immature gastrointestinal systems, leaving them predisposed to complications such as necrotizing enterocolitis (NEC). This potentially serious condition, in which the cells lining the bowel wall are injured, can occur in premature babies after they start feeding. Premature babies who receive only breast milk have a much lower risk of developing NEC.

· Blood problems:

Preemies are at risk of blood problems such as anemia and infant jaundice. Anemia is a common condition in which the body doesn't have enough red blood cells. While all newborns experience a slow drop in red blood cell count during the first months of life, the decrease may be greater in preemies, especially if your baby has a lot of blood taken for lab tests.

Infant jaundice is a yellow discoloration in a newborn baby's skin and eyes that occurs because the baby's blood contains an excess of a yellow-colored pigment from the liver or red blood cells (bilirubin).

· Metabolism problems:

Premature babies often have problems with their metabolism. Some preemies may develop an abnormally low level of blood sugar (hypoglycemia). This can happen because preemies typically have smaller stores of glycogen (stored glucose) than do full-term babies and because preemies' immature livers have trouble converting stored glycogen into glucose.

· Immune system problems:

An underdeveloped immune system, common in premature babies, can lead to infection. Infection in a premature baby can quickly spread to the bloodstream causing sepsis, a life-threatening complication.

Long-Term Complications:

In the long term, premature birth may lead to these complications:

· Cerebral palsy:

Cerebral palsy is a disorder of movement, muscle tone or posture that can be caused by infection, inadequate blood flow or injury to a preemie's developing brain either during pregnancy or while the baby is still young and immature.

· Impaired cognitive skills:

Premature babies are more likely to lag behind their full-term counterparts on various developmental milestones. Upon school age, a child who was born prematurely might be more likely to have learning disabilities.

· Vision problems:

Premature infants may develop retinopathy of prematurity, a disease that occurs when blood vessels swell and overgrow in the light-sensitive layer of nerves at the back of the eye (retina). Sometimes the abnormal retinal vessels gradually scar the retina, pulling it out of position. When the retina is pulled away from the back of the eye, it's called retinal detachment, a condition that, if undetected, can impair vision and cause blindness.

· Hearing problems:

Premature babies are at increased risk of some degree of hearing loss. All babies will have their hearing checked before going home.

· Dental problems:

Preemies who have been critically ill are at increased risk of developing dental problems, such as delayed tooth eruption, tooth discoloration and improperly aligned teeth.

· Behavioral and psychological problems:

Children who experienced premature birth may be more likely than full-term infants to have certain behavioral or psychological problems, such as attention-deficit/hyperactivity disorder (ADHD).

Chronic Health Complication:

Premature babies are more likely to have chronic health issues — some of which may require hospital care — than are full-term infants. Infections, asthma and feeding problems are more likely to develop or persist. Premature infants are also at increased risk of sudden infant death syndrome (SIDS).²³

Management:

Tertiary interventions are aimed at women who are about to go into preterm labor, or rupture the membranes or bleed preterm. The use of the fibronectin test and ultrasonography improves the diagnostic accuracy and reduces false-positive diagnosis. While treatments to arrest early labor where there is progressive cervical dilatation and effacement will not be effective to gain sufficient time to allow the fetus to grow and mature further, it may defer delivery sufficiently to allow the mother to be brought to a specialized center that is equipped and staffed to handle preterm deliveries. In a hospital setting women are hydrated via intravenous infusion (as dehydration can lead to premature uterine contractions.

Glucocorticosteroids:

Severely premature infants may have underdeveloped lungs, because they are not yet producing their own surfactant. This can lead directly to respiratory distress syndrome, also called hyaline membrane disease, in the neonate. To try to reduce the risk of this outcome, pregnant mothers with threatened premature delivery prior to 34 weeks are often administered at least one course of glucocorticoids, a steroid that crosses the placental barrier and stimulates the production of surfactant in the lungs of the fetus. Typical glucocorticoids that would be administered in this context are betamethasone or dexamethasone, often when the fetus has reached viability at 23 weeks. In cases where premature birth is imminent, a second "rescue" course of steroids may be administered 12 to 24 hours before the anticipated birth. Besides reducing respiratory distress, other neonatal complications are reduced by the use of glucocorticosteroids, namely intraventricular hemorrhage, necrotizing, and patent ductus arteriosus.²⁴

The routine administration of antibiotics to all women with threatened preterm labor reduces the risk of the baby to get infected with group B streptococcus and has been shown to reduce related mortality rates.

Tocolysis:

A number of medications may be useful to delay delivery including: NSAIDs, calcium channel blockers, beta mimetics, andatosiban. Tocolysis rarely delays delivery beyond 24–48 hours. This delay however may be sufficient to allow the pregnant women to be transferred to a center specialized for management of preterm deliveries and give administered corticosteroids the possibility to reduce neonatal organ immaturity. Meta-analyses indicate that calcium-channel blockers and an oxytocin antagonist can delay delivery by 2–7 days, and β2-agonist drugs delay by 48 hours but carry more side effects.¹⁸

When membranes rupture prematurely, obstetrical management looks for development of labor and signs of infection. Administration of corticosteroids is indicated prior to 32 weeks gestation. Prophylactic antibiotic administration has been shown to prolong pregnancy and reduced neonatal morbidity with rupture of membranes at less than 34 weeks.Because of concern about necrotizing enterocolitis, amoxicillin or erythromycin has been recommended.²⁵

Neonatal care:

After delivery, plastic wraps or warm mattresses are useful to keep the infant warm on their way to the NICU. In developed countries premature infants are usually cared for in a neonatal intensive care unit (NICU). In the NICU, premature babies are kept under radiant warmers or in incubators (also called isolettes), which are bassinets enclosed in plastic with climate control equipment designed to keep them warm and limit their exposure to germs. Modern neonatal intensive care involves sophisticated measurement of temperature, respiration, cardiac function, oxygenation, and brain activity. Treatments may include fluids and nutrition through intravenous catheters, oxygen supplementation, mechanical ventilation support, and medications. In developing countries where advanced equipment and even electricity may not be available or reliable, simple measures such as kangaroo care (skin to skin warming), encouraging breast feeding, and basic infection control measures can significantly reduce preterm morbidity and mortality.²⁶ Bili lights may also be used to treat newborn jaundice (hyperbilirubinemia). Prophylactic treatments are also used to care for preterm infants. For example, indomethacin (a prostaglandin inhibitor) is commonly used to help with the closure of a patent ductus arteriosus (PDA).

NURSING MANAGEMENT:

· Assess the mother’s condition and evaluate-signs of labor.

· Obtain a thorough obstetric history.

· Obtain specimens for complete blood count and urinalysis.

· Determine frequency, duration, and intensity of uterine contractions.

· Determine cervical dilation and effacement.

· Assess status of membranes and bloody show.

· Evaluate the fetus for distress, size, and maturity (Sonography and lecithin-sphingomyelin ratio)

· Perform measures to manage or stop preterm labor.

· Place the client on bed rest in the side-lying position.

· Prepare for possible ultrasonography, amniocentesis, tocolytic drug therapy, and steroid therapy.

· Administer tocolytic (contraction-inhibiting) medications as prescribed.

· Assess for side effects of tocolytic therapy (eg, decreased maternal blood pressure, dyspnea, chest pain, and FHR exceeding 180 beats/min)

· Provide physical and emotional support. Provide adequate hydration

· Provide client and family education

· After labor monitor vital signs of the baby.

· Administration of oxygen and maintenance of airway.

· Care of the baby under incubator.

· Maintaining fluid and electrolyte imbalance.

· Administration of antibiotics to reduce and prevent infection.

· Encourage breast feeding and kangaroo care.

NURSING DIAGNOSIS:

· Impaired gas exchange

· Ineffective thermoregulation related to prematurity

· Imbalanced nutrition

· Altered growth and development related to hospitalization

· Altered parenting

· Anxiety related to lack of knowledge

CONCLUSION:

Preterm birth is one of the most significant problems in perinatology. The findings of this analysis point towards the need to focus on identification of risk factors and preventive interventions in the disadvantaged regions of the world where the concentration of preterm births is highest. Moreover, striking inequalities exist between developed and developing countries in terms of the survival chances of a preterm infant. In many developing countries, infants weighing less than 2000 g (corresponding to about 32 weeks of gestation in the absence of intrauterine growth retardation) have little chance of survival. In contrast, the survival rate of infants born at 32 weeks in developed countries is similar to that of infants born at term.

REFERENCES:

1. Stacy Beck, Daniel Wojdyla, Lale Say et.al. Bulletin of the World Health Organization 2010; 88:31-38. doi: 10.2471/BLT.08.062554, 25 sep. 2009.

2. World Health Organization (November 2013). "Preterm birth". WHO. Int. Retrieved 19 September 2014.

3. Betrán AP, Say L, Gülmezoglu AM, Allen T, Hampson L. Effectiveness of different databases in identifying studies for systematic reviews: experience from the WHO systematic review of maternal morbidity and mortality. BMC Med Res Methodol 2005; 5: 6- doi: 10.1186/1471-2288-5-6 pmid: 15679886.

4. Saigal S, Doyle LW (2008). "An overview of mortality and sequelae of preterm birth from infancy to adulthood". The Lancet 371(9608): 261–269. doi:10.1016/S0140-6736(08)60136-1. ISSN 0140-6736. PMID 18207020.

5. Simhan HN, Caritis SN (2007). "Prevention of Preterm Delivery". New England Journal of Medicine 357 (5): 477–487.doi:10.1056/NEJMra050435. PMID 17671256.

6. Goldenberg RL, Culhane JF, Iams JD, Romero R (2008). "Epidemiology and causes of preterm birth". The Lancet 371 (9606): 75–84. doi:10.1016/S0140-6736(08)60074-4. PMID 18177778.

7. "The Care of Women Requesting Induced Abortion" (PDF). Evidence-based Clinical Guideline No. 7. Royal College o Obstetricians and Gynaecologists. November 2011. pp. 44, 45. Retrieved May 31, 2013.

8. Cholesterol Lowering Diet for Pregnant Women May Help Prevent Preterm Birth. British Medical Journal 331: 1093. 2005.doi:10.1136/bmj.331.7525.0-e.

9. Mercer BM, Goldenberg RL, Moawad AH, Meis PJ, Iams JD, Das AF, Caritis SN, Miodovnik M, Menard MK, Thurnau GR, Dombrowski MP, Roberts JM, McNellis D (1999). "The preterm prediction study: effect of gestational age and cause of preterm birth on subsequent obstetric outcome". American Journal of Obstetrics and Gynecology 181 (5 Pt 1): 1216–1221.doi:10.1016/S0002-9378(99)70111-0. PMID 10561648.

10. Winkvist A, Mogren I, Högberg U (1998). "Familial patterns in birth characteristics: impact on individual and population risks".International Journal of Epidemiology 27 (2): 248–254. doi:10.1093/ije/27.2.248. PMID 9602406.

11. Pinborg A, Wennerholm UB, Romundstad LB, Loft A, Aittomaki K, Söderström-Anttila V, Nygren KG, Hazekamp J, Bergh C (2012). "Why do singletons conceived after assisted reproduction technology have adverse perinatal outcome? Systematic review and meta-analysis". Human Reproduction Update 19 (2): 87–104. doi:10.1093/humupd/dms044. PMID 23154145.

12. Acién P (1993). "Reproductive performance of women with uterine malformations". Human Reproduction 8 (1): 122–126.PMID 8458914.

13. Marz 2014: Effect of smoke-free legislation on perinatal and child health: a systematic review and meta-analysis. This study is registered with PROSPERO, number CRD42013003522

14. Goldenberg RL, Hauth JC, Andrews WW (2000). "Intrauterine infection and preterm delivery". New England Journal of Medicine 342 (20): 1500–1507. doi:10.1056/NEJM200005183422007. PMID 10816189.

15. Lee SE, Park JS, Norwitz ER, Kim KW, Park HS, Jun JK. Measurement of placental a-microglobulin-1 in cervicovaginal discharge to diagnose rupture of membranes. Obstet Gynecol 2007;109:634–640.

16. Leitich H, Brunbauer M, Kaider A, Egarter C, Husslein P (1999). "Cervical length and dilatation of the internal cervical os detected by vaginal ultrasonography as markers for preterm delivery: A systematic review". American Journal of Obstetrics and Gynecology 181 (6): 1465–1472. doi:10.1016/S0002-9378(99)70407-2. PMID 10601930.

17. Been JV, Nurmatov UB, Cox B, Nawrot TS, van Schayck CP, Sheikh A (May 3, 2014). "Effect of smoke-free legislation on perinatal and child health: a systematic review and meta-analysis.". Lancet 383 (9928): 1549–60. doi:10.1016/S0140-6736(14)60082-9. PMID 24680633.

18. Ugboma HA, Akani CI (2004). "Abdominal massage: another cause of maternal mortality". Niger J Med 13 (3): 259–62. PMID 15532228

19. https://www.unitedconcordia.com/dental insurance/dental/conditions/pregnancy-oral-health/

20. Lee SM, Lee J, Seong HS, Lee SE, Park JS, Romero R, Yoon BH. The clinical significance of a positive Amnisure test TM in women with term labor with intact membranes. J Matern Fetal Neonatal Med 2009;22:305–310.

21. Lee SM, Lee J, Seong HS, Lee SE, Park JS, Romero R, Yoon BH. The clinical significance of a positive Amnisure test TM in women with term labor with intact membranes. J Matern Fetal Neonatal Med 2009; 22:305–310.

22. Nikolova T, Bayev O, Nikolova N, Di Renzo GC. Comparison of a novel test for placental alpha microglobulin-1 with fetal fibronectin and cervical length measurement for the prediction of imminent spontaneous preterm delivery in patients with threatened preterm labor. J Perinat Med. 2015 Jan 6.

23. http://www.mayoclinic.org/diseases-conditions/premature-birth/basics/definition/con-20020050

24. Leitich H, Brunbauer M, Kaider A, Egarter C, Husslein P (1999). "Cervical length and dilatation of the internal cervical os detected by vaginal ultrasonography as markers for preterm delivery: A systematic review". American Journal of Obstetrics and Gynecology 181 (6): 1465–1472.

25. Hoyme UB, Saling E (2004). "Efficient prematurity prevention is possible by pH-self measurement and immediate therapy of threatening ascending infection". European Journal of Obstetrics and Gynecology and Reproductive Biology 115 (2): 148–153.doi:10.1016/j.ejogrb.2004.02.038

26. Phibbs CS, Baker LC, Caughey AB, Danielsen B, Schmitt SK, Phibbs RH (2007). "Level and volume of neonatal intensive care and mortality in very-low-birth-weight infants" New England Journal of Medicine 356 (21): 2165–2175.

Received on 16.04.2015 Modified on 23.04.2015

Int. J. Adv. Nur. Management 3(2): April- June, 2015; Page 179-186