Influence of Smoking and Alcohol during Pregnancy on Outcome of VLBW Infants

Are Babies Born Preterm High-Risk Asthma Candidates?

Among preterm infants, the risk of developing asthma is a matter of debate. This review discusses the state of the art of poorly understood prematurity-associated asthma. Impaired pulmonary function is common in children born prematurely. Preterm infants are prone to developing viral respiratory tract infections, bronchiolitis in the first year of life, and recurrent viral wheezing in preschool age. All of these conditions may precede asthma development. We also discuss the role of both atopic sensitization and intestinal microbiome and, consequently, immune maturation. Diet and pollution have been considered to better understand how prematurity could be associated with asthma. Understanding the effect of factors involved in asthma onset may pave the way to improve the prediction of this asthma phenotype.

Retinopathy of prematurity: contribution of inflammatory and genetic factors

Retinopathy of prematurity (ROP) is a retinal vasoproliferative disorder that represents an important cause of childhood visual impairment and blindness. Although oxidative stress has long been implicated in ROP etiology, other prenatal and perinatal factors are also involved. This review focuses on current research involving inflammation and genetic factors in the pathogenesis of ROP. Increasing evidence suggests that perinatal inflammation or infection contributes to ROP pathogenesis. Cytokines and chemokines with a fundamental role in inflammatory responses and that significantly contributing to angiogenesis are analyzed. Microglia cells, the retinal-resident macrophages, are crucial for retinal homeostasis, however, under sustained pathological stimuli release exaggerated amounts of inflammatory mediators and can promote pathological neovascularization. Current modulation of angiogenic cytokines, such as treatment with antibodies to vascular endothelial growth factor (anti-VEGF), has shown efficacy in the treatment of ocular neovascularization; however, some patients are refractory to anti-VEGF agents, suggesting that other angiogenic or anti-angiogenic cytokines need to be identified. Much evidence suggests that genetic factors contribute to the phenotypic variability of ROP. Several studies have implicated the involvement of candidate genes from different signaling pathways in the development of ROP. However, a genetic component with a major impact on ROP has not yet been discovered. Most studies have limitations and did not replicate results. Future research involving bioinformatics, genomics, and proteomics may contribute to finding more genes associated with ROP and may allow discovering better solutions in the management and treatment of ROP.

How to prevent ROP in preterm infants in Indonesia?

BACKGROUND AND AIMS

Retinopathy of prematurity (ROP) is a severe disease in preterm infants. It is seen more frequently in Low-Middle Income Countries (LMIC) like Indonesia compared to High-Income Countries (HIC). Risk factors for ROP development are -extreme- preterm birth, use of oxygen, neonatal infections, respiratory problems, inadequate nutrition, and blood and exchange transfusions. In this paper, we give an overview of steps that can be taken in LMIC to prevent ROP and provide guidelines for screening and treating ROP.

METHODS

Based on the literature search and data obtained by us in Indonesia's studies, we propose guidelines for the prevention, screening, and treatment of ROP in preterm infants in LMIC.

RESULTS

Prevention of ROP starts before birth with preventing preterm labor, transferring a mother who might deliver <32 weeks to a perinatal center and giving corticosteroids to mothers that might deliver <34 weeks. Newborn resuscitation must be done using room air or, in the case of very preterm infants (<29-32 weeks) by using 30% oxygen. Respiratory problems must be prevented by starting continuous positive airway pressure (CPAP) in all preterm infants <32 weeks and in case of respiratory problems in more mature infants. If needed, the surfactant should be given in a minimally invasive manner, as ROP's lower incidence was found using this technique. The use of oxygen must be strictly regulated with a saturation monitor of 91-95%. Infections must be prevented as much as possible. Both oral and parenteral nutrition should be started in all preterm infants on day one of life with preferably mothers' milk. Blood transfusions can be prevented by reducing the amount of blood needed for laboratory analysis.

DISCUSSION

Preterm babies should be born in facilities able to care for them optimally. The use of oxygen must be strictly regulated. ROP screening is mandatory in infants born <34 weeks, and infants who received supplemental oxygen for a prolonged period. In case of progression of ROP, immediate mandatory treatment is required.

CONCLUSION

Concerted action is needed to reduce the incidence of ROP in LMIC. "STOP - R1O2P3" is an acronym that can help implement standard practices in all neonatal intensive care units in LMIC to prevent development and progression.

Hospitalizations and mortality among patients with fetal alcohol spectrum disorders: a prospective study

With nearly 10% of women consuming alcohol during pregnancy, fetal alcohol spectrum disorders (FASDs) are becoming an increasing concern for clinicians and policymakers interested in the field of healthcare. Known as the range of mental and/or physical disabilities that occur among individuals with prenatal alcohol exposure, FASDs can result in dysmorphic features, problems with physical growth, neurobehavioral and cognitive problems that not only increase risk of various diseases, but also premature mortality. We investigated whether the diagnosis of FASDs result in increased risk of hospitalizations and mortality, with respect to FASD domains and relative diseases, when age effects are controlled for. The data for this study was taken from the National Health Insurance Service – National Sample Cohort (NHIS-NSC) between 2003 and 2013. The population attributable risk (PAR) statistic was used to estimate the percentage of hospitalizations and mortality attributable to FASDs and other factors. A time-dependent Cox proportional hazards model with age of diagnosis as the time-scale was employed to calculate adjusted hazard ratios and 95% CIs for hospitalizations and mortality among FASD populations compared to their general population peers. Among the 3,103 FASD cases, 27.5% experienced hospitalizations and 12.5% died. Overall, FASDs accounted for 853 FASD-attributable hospitalizations (51.0% of all hospitalizations in the study population) and 387 mortality events (34.5% of all deaths in the study population). 20.52% of hospitalizations and 21.35% of mortalities were attributable to FASDs in this population. Compared to the control group, FASD patients had a 1.25-fold (HR: 1.25, 95% CI: 1.05–1.49, p = 0.0114) increased risk of hospitalizations and a 1.33-fold (HR: 1.33, 95% CI: 1.07–1.67, p = 0.0118) increased risk of all-cause mortality. The most common cause for hospitalization was diseases of the nervous system, which accounted for 450 FASD-attributable hospitalizations (96.2% of all nervous system hospitalizations in the study population). In fact, FASD patients were 52 times more likely to be hospitalized for nervous system diseases than their peers (HR: 51.78, 95% CI: 29.09–92.17, p < .0001). The most common cause for mortality was neoplasms, which accounted for 94 FASD-attributable deaths (28.7% of all neoplasm deaths in the study population). However, FASD patients did not have increased risk of neoplasm mortality than the general population (HR: 0.88, 95% CI: 0.59–1.32, p < .0001). Overall, this study found that individuals diagnosed with FASDs have increased risk of both hospitalizations and mortality, compared to their general population peers. This is particularly so for diseases of the nervous system, which showed a 52-fold increase in hospitalizations and four-fold increase in mortality for FASD patients in our study. Likewise, while the association between FASDs and neoplasm mortality was not significant in our investigation, more attention by neurologists and related healthcare providers regarding the link between these two factors is necessary.

Trial Registration: Institutional Review Board of Yonsei University’s Health System: Y-2019-0174.

Small for gestational age very preterm infants present a higher risk of developing bronchopulmonary dysplasia

INTRODUCTION

Several studies assessed the influence of a low birth weight on bronchopulmonary dysplasia (BPD), but not all could find a significant association. Our aim was to assess the association between low birth weight and BPD in preterm infants, prospectively recruited at 11 level III Portuguese neonatal centers.

METHODS

Obstetrical and neonatal data on mothers and preterm infants with gestational ages between 24 and 30 weeks, born during 2015 and 2016 after a surveilled pregnancy, were analyzed. Neonates were considered small for gestational age (SGA) when their birthweight was below the 10th centile of Fenton's growth chats and BPD was defined as the dependency for oxygen therapy until 36 weeks of corrected age. Statistical analysis was performed using IBM SPSS® statistics 23 and a p-value <0.05 was considered statistically significant.

RESULTS

Out of 614, a total of 494 preterm infants delivered from 410 women were enrolled in the study; 40 (8.0%) infants with SGA criteria. SGA were more often associated with a single pregnancy, had greater use of antenatal corticosteroids, increased prevalence of gestational hypertensive disorders, C-section, rupture of membranes below 18 hours, rate of intubation in the delivery room, use of surfactant treatment, oxygen therapy, mechanical ventilation need, BPD, cystic periventricular leukomalacia, nosocomial sepsis and pneumonia; had lower prevalence of chorioamnionitis, and lower Apgar scores. The multivariate analysis by logistic regression, adjusted for BPD risk factors revealed a significant association between SGA and BPD: OR = 5.2 [CI: 1.46-18.58]; p = 0.01.

CONCLUSION

The results of this study increase the scientific evidence that SGA is an independent risk factor for BPD.

Maternal smoking as an independent risk factor for the development of severe retinopathy of prematurity in very preterm infants

BACKGROUND/OBJECTIVES

Retinopathy of prematurity (ROP) is a severe neonatal complication potentially leading to visual impairment and blindness. Known risk factors include preterm birth, low birth weight and respiratory support. Limited and contradictory data exist on the risk of maternal smoking during pregnancy on the development of ROP. This study aims to investigate smoking as an independent risk factor for the development of severe ROP (≥stage 3).

SUBJECTS/METHODS

This is a single centre retrospective case-control study of prospectively collected clinical data of infants born before 32 weeks of gestation between 2001 and 2012 at a tertiary care university hospital. The association between maternal smoking during pregnancy and the development of severe ROP was analyzed by multivariate logistic regression.

RESULTS

In total, n = 751 infants born < 32 weeks of gestation were included in this study. In total, 52.9% (n = 397) were diagnosed with ROP and 10.8% (n = 81) developed ROP ≥ stage 3. In total, 8.4% (n = 63) mothers presented with a history of smoking during pregnancy, which was associated to a higher rate of ROP (OR 2.59, 95% CI 1.10-6.12). Low gestational age, low birth weight and prolonged respiratory support were confirmed as independent risk factors for the development of severe ROP.

CONCLUSIONS

To date, this is the largest study evaluating the effect of maternal smoking on the development of ROP. Maternal smoking during pregnancy is identified as an independent risk factor for the development of severe ROP in preterm infants born < 32 weeks of gestation.

Tobacco Smoking During Pregnancy Is Associated With Increased Risk of Moderate/Severe Bronchopulmonary Dysplasia: A Systematic Review and Meta-Analysis

Epidemiological evidence and animal studies support that intrauterine exposure to tobacco smoke disturbs lung development and has a negative effect in the pulmonary health of the offspring. Individual studies suggest an association between fetal exposure to maternal smoking and risk of developing bronchopulmonary dysplasia (BPD). However, this association has not yet been systematically investigated. We aimed to conduct a systematic review of studies reporting on tobacco smoking during pregnancy as potential risk factor for BPD. PubMed/MEDLINE and EMBASE databases were searched. BPD was defined as requirement of supplemental oxygen on postnatal day 28 (BPD28; all BPD), at the postmenstrual age (PMA) of 36 weeks (BPD36; moderate/severe BPD), or as requirement of more than 30% oxygen and/or positive pressure at 36 weeks PMA (severe BPD). Pooled risk ratios (RR) and 95% confidence intervals (CI) were calculated using a random-effects model. Of 2,894 potentially relevant studies, 33 met the inclusion criteria. The included studies evaluated 171,772 infants and included 30,445 cases of exposure to maternal smoking and 25,340 cases of BPD of any severity. Meta-analysis showed a significant association between tobacco smoking during pregnancy and BPD36 (17 studies, RR 1.126, 95% CI 1.008-1.259, p = 0.036), but could not demonstrate a significant association between tobacco smoking during pregnancy and BPD28 (16 studies, RR 1.021, 95% CI 0.924-1.129, p = 0.681), or severe BPD (3 studies, RR 1.143, 95% CI 0.528-2.478, p = 0.734). In conclusion, our data suggest that tobacco smoking during pregnancy increases the risk of moderate/severe BPD. Our results highlight the detrimental effects of tobacco smoking and reinforce the hypothesis of the involvement of prenatal insults in the etiopathogenesis of BPD.

Phenotypic overlap in neonatal respiratory morbidity following preterm premature rupture of membranes versus spontaneous preterm labor

BACKGROUND

Bronchopulmonary dysplasia (BPD), a major source of morbidity in premature neonates, has been associated with intrauterine infection and preterm birth. Both preterm premature rupture of membranes (PPROM) and spontaneous preterm labor (sPTL) are linked with intrauterine inflammation. Whether PPROM and sPTL, as two phenotypic categories of preterm birth, are associated with exposure to different degrees and durations of inflammation that might impact fetal lung development is unknown. PPROM may be associated with longer latency until delivery, which is beneficial for neonatal mortality, but may impart greater injury risk to the developing fetal lungs. It is unknown if PPROM is associated with a greater risk of adverse neonatal respiratory outcomes than sPTL.

OBJECTIVE

The objective of this study was to determine if PPROM imparts a differentially greater risk for neonatal BPD than sPTL. A secondary objective was to determine if PPROM was associated with a greater risk of adverse neonatal respiratory outcomes other than BPD and whether gestational latency following PPROM or sPTL diagnosis constitutes a risk factor for fetal lung injury.

STUDY DESIGN

We conducted a retrospective secondary analysis of a large cohort of women at risk for spontaneous preterm birth, who were originally enrolled in a randomized controlled trial of magnesium sulfate versus placebo examining neuroprotection. For our study, we included women with a singleton pregnancy complicated by PPROM or sPTL and delivery between 24 and 34 weeks gestational age. Cases with multiple gestation, congenital anomalies, maternal seropositivity for human immunodeficiency virus, or hypertensive diseases of pregnancy (including preeclampsia) were excluded. The primary outcome was BPD. Secondary outcomes were respiratory distress syndrome (RDS), transient tachypnea of the newborn (TTN), requirement for mechanical ventilation, pneumonia, neonatal sepsis, fetal or neonatal death, and a composite of adverse neonatal respiratory outcomes including (BPD, pneumonia, RDS, and TTN). Statistical analyses included chi-square, Student's t-test and logistic and multiple regression.

RESULTS

A total of 1729 women were included in this analysis including 1554 with PPROM and 175 with sPTL. Women in the PPROM group were more likely to be older, not of Hispanic race, married, more educated, have smoked during pregnancy and have a greater body mass index. The BPD rate was not significantly different following PPROM versus sPTL. Neonates in the PPROM group experienced a lower rate of pneumonia (p = .001), neonatal sepsis (p = .009) and patent ductus arterious (PDA) requiring either medical or surgical therapy (p < .001) than neonates in the sPTL group. Chorioamnionitis was more common in the PPROM group (p = .008) than the sPTL group. After multivariable logistic regression with BPD or composite of adverse neonatal respiratory outcomes as the dependent outcomes, and controlling for gestational age at delivery, maternal smoking history, duration of mechanical ventilation and RDS, there was no significant difference between PPROM and sPTL.

CONCLUSIONS

BPD rates were not significantly different in neonates born to women following PPROM versus sPTL. However, PPROM was associated with lower rates of pneumonia, neonatal sepsis, and PDA requiring therapy in the univariate analysis, but not the multivariate analysis. Neonatal respiratory outcomes may have a similar phenotypic overlap regardless of whether preterm birth follows PPROM or sPTL.

Retinopathy of prematurity: a review of risk factors and their clinical significance

Retinopathy of prematurity (ROP) is a retinal vasoproliferative disease that affects premature infants. Despite improvements in neonatal care and management guidelines, ROP remains a leading cause of childhood blindness worldwide. Current screening guidelines are primarily based on two risk factors: birth weight and gestational age; however, many investigators have suggested other risk factors, including maternal factors, prenatal and perinatal factors, demographics, medical interventions, comorbidities of prematurity, nutrition, and genetic factors. We review the existing literature addressing various possible ROP risk factors. Although there have been contradictory reports, and the risk may vary between different populations, understanding ROP risk factors is essential to develop predictive models, to gain insights into pathophysiology of retinal vascular diseases and diseases of prematurity, and to determine future directions in management of and research in ROP.

Bronchopulmonary dysplasia: A review of pathogenesis and pathophysiology

Bronchopulmonary dysplasia (BPD) is a chronic lung disease of primarily premature infants that results from an imbalance between lung injury and repair in the developing lung. BPD is the most common respiratory morbidity in preterm infants, which affects nearly 10, 000 neonates each year in the United States. Over the last two decades, the incidence of BPD has largely been unchanged; however, the pathophysiology has changed with the substantial improvement in the respiratory management of extremely low birth weight (ELBW) infants. Here we have attempted to comprehensively review and summarize the current literature on the pathogenesis and pathophysiology of BPD. Our goal is to provide insight to help further progress in preventing and managing severe BPD in the ELBW infants.

Antenatal Determinants of Bronchopulmonary Dysplasia and Late Respiratory Disease in Preterm Infants

RATIONALE

Mechanisms contributing to chronic lung disease after preterm birth are incompletely understood.

OBJECTIVES

To identify antenatal risk factors associated with increased risk for bronchopulmonary dysplasia (BPD) and respiratory disease during early childhood after preterm birth, we performed a prospective, longitudinal study of 587 preterm infants with gestational age less than 34 weeks and birth weights between 500 and 1,250 g.

METHODS

Data collected included perinatal information and assessments during the neonatal intensive care unit admission and longitudinal follow-up by questionnaire until 2 years of age.

MEASUREMENTS AND MAIN RESULTS

After adjusting for covariates, we found that maternal smoking prior to preterm birth increased the odds of having an infant with BPD by twofold (P = 0.02). Maternal smoking was associated with prolonged mechanical ventilation and respiratory support during the neonatal intensive care unit admission. Preexisting hypertension was associated with a twofold (P = 0.04) increase in odds for BPD. Lower gestational age and birth weight z-scores were associated with BPD. Preterm infants who were exposed to maternal smoking had higher rates of late respiratory disease during childhood. Twenty-two percent of infants diagnosed with BPD and 34% of preterm infants without BPD had no clinical signs of late respiratory disease during early childhood.

CONCLUSIONS

We conclude that maternal smoking and hypertension increase the odds for developing BPD after preterm birth, and that maternal smoking is strongly associated with increased odds for late respiratory morbidities during early childhood. These findings suggest that in addition to the BPD diagnosis at 36 weeks, other factors modulate late respiratory outcomes during childhood. We speculate that measures to reduce maternal smoking not only will lower the risk for preterm birth but also will improve late respiratory morbidities after preterm birth.

Reducing tobacco smoking and smoke exposure to prevent preterm birth and its complications

Tobacco smoking and smoke exposure during pregnancy are associated with a range of adverse health outcomes, including preterm birth. Also, children born preterm have a higher risk of complications including bronchopulmonary dysplasia and asthma when their mothers smoked during pregnancy. Smoking cessation in early pregnancy can help reduce the adverse impact on offspring health. Counselling interventions are effective in promoting smoking cessation and reducing the incidence of preterm birth. Peer support and incentive-based approaches are likely to be of additional benefit, whereas the effectiveness of pharmacological interventions, including nicotine replacement therapy, has not definitely been established. Smoke-free legislation can help reduce smoke exposure as well as maternal smoking rates at a population level, and is associated with a reduction in preterm birth. Helping future mothers to stop smoking and protect their children from second hand smoke exposure must be a key priority for health care workers and policy makers alike.

Morbidity and mortality trends in very-very low birth weight premature infants in light of recent changes in obstetric care

OBJECTIVE

In this study, we describe trends in morbidity and mortality of preterm infants with less than 500mg birth weight in the changing landscape of obstetric and neonatal care.

STUDY DESIGN

During a ten year study period between 2006 and 2016 we assessed outcome data for all neonates with less than 500mg birth weight born at our Neonatal Intensive Care Unit. We divided study subjects into two groups based on whether their birth date fell in the first half (2006-2010; n=39) versus the second half (2011-2015; n=27) of the study period comparing clinical outcomes in the two groups. We also assessed several clinical parameters for association with postnatal survival by comparing relative frequencies for each clinical parameter among surviving infants versus mortality cases.

RESULTS

Survival rate for preterm neonates with less than 500mg birth weight born between 2006 and 2010 was 30.8%. This survival rate rose to 70.4% in the second half of the study period between 2011 and 2015 (p<0.05). Among surviving babies premature birth was found to be predominantly associated with maternal hypertension or intrauterine growth restriction while in those who died premature birth due to premature rupture of membranes and spontaneous preterm labor were significantly more common. All surviving infants with less than 500mg birth weight were born via cesarean section whereas among those who died cesarean section had been performed in only 80% and vaginal delivery in 20% representing a significant difference between the groups (p<0.05). The majority (90.3%) of surviving infants with less than 500mg birth weight had received surfactant therapy while the proportion of neonates receiving surfactant therapy among mortality cases was significantly lower (65.2%; p<0.05).

DISCUSSION

Our findings suggest that among premature neonates with less than 500mg birth weight preterm delivery due to premature rupture of membranes and intrauterine infections represents the worse mortality risk. Steroid prophylaxis and measures to prevent and treat intrauterine infections with appropriate use of antibiotics can markedly improve survival in these cases. In premature neonates with less than 500mg birth weight survival is more favorable after cesarean section compared to vaginal delivery.

Parent-related mechanisms underlying the social gradient of childhood overweight and obesity: a systematic review

BACKGROUND

Low socio-economic status (SES) is a significant risk factor for childhood overweight and obesity (COWOB) in high-income countries. Parents to young children buffer and accentuate social and cultural influences, and are central to the development of this disease. An understanding of the parent-related mechanisms that underlie the SES-COWOB relationship is needed to improve the efficacy of prevention and intervention efforts.

OBJECTIVE

A systematic review of relevant literature was conducted to investigate the mechanisms by which levels of SES (low, middle and high) are associated to COWOB, by exploring mediation and interaction effects.

METHOD

Six electronic databases were searched yielding 5155 initial records, once duplicates were removed. Studies were included if they investigated COWOB, SES, parent-related factors and the multivariate relationship between these factors. Thirty studies were included. Factors found to be mediating the SES-COWOB relationship or interacting with SES to influence COWOB were categorized according to an ecological systems framework, at child, parent, household and social system level factors.

RESULTS

High parent body mass index, ethnicity, child-care attendance, high TV time (mother and child), breastfeeding (early weaning), food intake behaviours and birthweight potentially mediate the relationship between SES and COWOB. Different risk factors for COWOB in different SES groups were found. For low SES families, parental obesity and maternal depressive symptoms were strong risk factors for COWOB, whereas long maternal working hours and a permissive parenting style were risk factors for higher SES families. None of the studies investigated parental psychological attributes such as attitudes, beliefs, self-esteem and so on as potential mechanisms/risk factors.

CONCLUSIONS

Families from different SES groups have different risk and protective factors for COWOB. Prevention and intervention efforts may have improved efficacy if they are tailored to address specific risk factors within SES.

Epidemiology of substance-exposed pregnancies at one Great Lakes hospital that serves a large number of American Indians

OBJECTIVE

The purpose of this research was to determine the prevalence of substance-exposed pregnancies at a hospital in the Great Lakes region of the U.S.

METHOD

Data were collected via retrospective chart abstractions of patients who were seen for delivery at one Great Lakes region hospital during a 1-year period who were given at least one of the International Classification of Diseases codes related to substance use.

RESULTS

A total of 342 medical records were included in the analysis, and, while much race/ethnicity data were missing, a large percentage of those in our analysis identified as American Indian. The prevalence of substance-exposed pregnancies at this hospital during a 1-year period was 34.5%. The majority (84.8%) were tobacco users, and many were found to have multiple substance exposures. Also, 48.5% were found to have a mental health diagnosis in addition to substance use.

CONCLUSIONS

Data from this project can be used in prevention efforts, including preconception care for women at risk for substance use and mental health issues.

Impact of smoke-free legislation on perinatal and infant mortality: a national quasi-experimental study

Smoke-free legislation is associated with improved early-life outcomes; however its impact on perinatal survival is unclear. We linked individual-level data with death certificates for all registered singletons births in England (1995–2011). We used interrupted time series logistic regression analysis to study changes in key adverse perinatal events following the July 2007 national, comprehensive smoke-free legislation. We studied 52,163 stillbirths and 10,238,950 live-births. Smoke-free legislation was associated with an immediate 7.8% (95%CI 3.5–11.8; p < 0.001) reduction in stillbirth, a 3.9% (95%CI 2.6–5.1; p < 0.001) reduction in low birth weight, and a 7.6% (95%CI 3.4–11.7; p = 0.001) reduction in neonatal mortality. No significant impact on SIDS was observed. Using a counterfactual scenario, we estimated that in the first four years following smoke-free legislation, 991 stillbirths, 5,470 cases of low birth weight, and 430 neonatal deaths were prevented. In conclusion, smoke-free legislation in England was associated with clinically important reductions in severe adverse perinatal outcomes.

Epidemiology and Clinical Research Design, Part 2: Principles

This is the third article covering core knowledge in scholarly activities for neonatal physicians. In this article, we discuss various principles of epidemiology and clinical research design. A basic knowledge of these principles is necessary for conducting clinical research and for proper interpretation of studies. This article reviews bias and confounding, causation, incidence and prevalence, decision analysis, cost-effectiveness, sensitivity analysis, and measurement.