low birthweight/ preterm birth: issues and research needs
TRANSCRIPT
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Low Birthweight/ Preterm Birth: Issues and Research Needs
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Issues in LBW/Prematurity
Increasing rates / Incidence Consequences Etiologies Risk Factors Markers Prevention strategies Research needs and focus
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Preterm Delivery: A Public Health Priority 1 in 8 infants are born preterm
476,000 preterm births each year leading cause of hospitalization among pregnant women leading cause of death among African-American infants associated with developmental disabilities
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Source: Centers for Disease Control and Prevention, National Center for Health Statistics, National Vital Statistics System
.
: -
0
2
4
6
8
10
12
14
1981 1985 1990 1995 2002
Per
cen
t
Preterm (<37w)
Low birthweight(< 2500 gm)
US 1981-2002: Percent Preterm and LBW
• Preterm birth increased 29% since 1981
• LBW increased 15% since 1981
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22% more twinbirths had PTD in 1996-7 than 1981-2
US 1980-2000: Twin Births
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5
10
15
20
1998 1999 2000 2001
Disparity in preterm birth: race and ethnicity
American Indian/Alaska Native
Asian
TotalHispanic
Native Hawaiian/Other Pacific Islander
Percent
SOURCE: National Vital Statistics System – Natality NCHS, CDC.
Black, Not Hispanic
White,Not Hispanic
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Leading Causes of Neonatal Mortality, 2001
0 5 10 15 20 25
Preterm / LBW
Birth Defects
Maternalcomplications
Placenta / cordcomplications
RDS
(N / 100,000 live births)
4,322
3,875
1,491
998
943
http://www.cdc.gov/nchs/data/nvsr/nvsr52/nvsr52_09.pdf Table H. Deaths and percentage of total deaths for the 10 leading causes of neonatal and postneonatal deaths: United States, 2001
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Gestation (weeks)
010
20
30
40
50
60
70
(%)
21 22 23 24 25 26
Serious Morbidity
Survival
N = 799
Grade 3-4 IVHGrade 3-4 ROPStage 3 NECSeizuresO2 dep @120d
Bottoms, 1995
Preterm Birth: Outcome1 out of 5 children with mental retardation1 out of 3 children with vision impairmentAlmost half of children with cerebral palsy
Accounts for
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Preterm Birth: Long Term Outcome For the baby:
Increased risk for cardiovascular disease (MI, stroke, hypertension) as an adult
Increased risk for diabetes as an adult Possible increase in cancer risk
For the mother: Increased risk for
subsequent preterm delivery
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Predictors of Preterm Birth
To initiate risk-specific treatment To define a population and evaluate an
intervention/therapy To learn mechanisms of preterm delivery
Importance of identification of markers
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Risk factors for PTD Shortened cervical length African American race Age (<17, >35)
Lifestyle risk factors: Late or no prenatal care Smoking Drinking alcohol Using illegal drugs Domestic violence Lack of social support High levels of stress Long working hours Low income
Medical risk factors: PROMInfections (UTI, vaginal infections, STD) High blood pressure Diabetes Clotting disorders (thrombophilia) Maternal weight (underweight or obesity) Short time period between pregnancies Certain birth defectsVaginal bleeding
Multiple gestation Previous preterm birth Uterine/cervical
abnormalities
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Women “at risk” for PTD
Prior spontaneous PTD Multiple gestation Uterine anomaly Cervical incompetence Socioeconomic status Biochemical markers (e.g. FFN) Shortened cervical length Vaginal / cervical infections /inflammation
0
10
20
30
40
50
60
Term/Term PTD/Term Term/PTD PTD/PTD
PTD(%)
PTD risk based on prior pregnancy
Salama et al 1994
n=889
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Risk Scoring Systems and PTD Low sensitivity, high false positive rates Majority of women who have PTD are
from a low risk group Identification of high risk status has not led
to improvement in outcome Importance of effective intervention for
risk factor / marker
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Categories of Preterm Births
Spontaneous preterm labor (56%)
Preterm premature rupture of the fetal membranes (20%)
Preterm deliveries indicated for fetal or maternal reasons (22%)
Spontaneous56%
PPROM20%
Indicated22%
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Uterine contractions
Rupture of membranes
infection
inflammation
Cytokines, chemokines
Cervical ripeningCervical effacementCervical dilation
Spontaneous Preterm Delivery: Mechanisms
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20 24 28 32 36 38 40 42
Etiology of Spontaneous PTB
InfectionInfectionOtherOther
PathologiesPathologiesNoNo
PathologyPathology
Gestational AgeGestational Age
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Infection and sPTD Evidence supports infection cause of PTD:
Clinical chorioamnionitis Subclinical chorioamnionitis
UreaplasmaMycoplasmaGardnerellaMobiluncusPeptostreptococcusBacteroides
Bacteria associatedwith prematurity
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Antibiotics: PTL & intact membranes Improved
Delayed Infant Study Antibiotic N Delivery Outcome
MacGregor, 1986 Erythromycin 17 Yes No
Morales, 1988 Erythromycin, Ampicillin 150 Yes No
Winkler, 1988 Erythromycin 19 Yes -
Newton, 1989 Erythromycin / Ampicillin 95 No No
MacGregor, 1991 Clindamycin 103 Yes No
McCaul, 1992 Ampicillin 40 No No
Romero, 1993 Ampicillin / Amoxicillin / Erythromycin 275 No No
Cox, 1995 Ampicillin / Amoxicillin 78 No No
Gordon, 1995 Ceftizoximine 117 No No
Norman, 1994 Metronidazole / Ampicillin 81 Yes Yes
Svare, 1997 Metronidazole / Ampicillin 110 Yes ?
Oracle Trial Erythromycin or Amoxicillin No No
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Antibiotics & BV
RCT metronidazole +BV with hx prior sPTDPTD 18% v 39%, p<.05 Morales et al 1994
RCT metronidazole+erythromycin in high risk women, +BVPTD 23% v 37%, p<.001 Hauth et al 1994
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NICHD: MFMU BV/TV Trial
Aim: To establish whether metronidazole therapy will reduce the risk of PTD in women with asymptomatic bacterial vaginosis or trichomonas vaginalis
Design: double-masked, placebo-controlled trial Eligibility criteria: <24 wks, BV or TV positive Intervention: Four doses of 2g metronidazole or placebo Primary outcome: delivery at < 37 weeks’ Sample: BV: 1900 pregnant women (950/group)
BV: Carey et al, N Engl J Med 2000TV: Klebanoff et al, N Engl J Med 2001
TV: 1900 pregnant women (950/group)
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Rates of Preterm Birth
0%
4%
8%
12%
16%
20%
<37 <35 <32
0%
4%
8%
12%
16%
20%
<37 <35 <32
Asymptomatic BVAsymptomatic BV Asymptomatic TVAsymptomatic TV
PlaceboMetronidazole
PTD
BV: Carey et al, N Engl J Med 2000TV: Klebanoff et al, N Engl J Med 2001
P<0.004
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BV/TV trials TV trial stopped by DSMC after interim
analysis found increased PTD in metronidazole group
Effectiveness of treatment BV: 78% negative for BV TV: 93% negative for trichonomiasis
BV: Carey et al, N Engl J Med 2000TV: Klebanoff et al, N Engl J Med 2001
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BV/TV trials: Conclusions Treatment of asymptomatic
BV does not reduce PTD or adverse perinatal outcomes
TV increased the risk of PTD
Results from these trials changed the practice of indiscriminate use of antibiotics in pregnancy
BV: Carey et al, N Engl J Med 2000TV: Klebanoff et al, N Engl J Med 2001
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Fetal Fibronectin (FFN) Membrane protein localized to area between fetus
and mother Role in implantation and placentation When detected in cervical or vaginal secretions of
asymptomatic women is associated with >50-fold increased risk in PTD<28wks
Intrauterine infection may disrupt fetal membranes and result in release of FFN
Goldenberg et al, Am J Obstet Gynecol 2000
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Antibiotics for FFN+ to prevent PTD Aim: To establish whether metronidazole therapy will
reduce the risk of PTD in FFN+ women Design: double-masked, placebo-controlled trial Eligibility criteria: FFN+ at 21-25 wks Intervention: 10 day course metronidazole and
erythromycin or placebo Primary outcome: delivery at < 37 weeks’ Sample: 715 pregnant women Findings: No improvement in sPTD or nn outcome
Andrews et al, Obstet Gynecol 2003
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Infection, Antibiotics and PTD
Infection with intact membranes +BV, high-risk women +BV, low risk women +TV +FFN
No
Yes
No
No
No
AntibioticsHelpful
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Home Uterine Contraction Monitoring to Prevent Preterm Delivery
2422 insured, at-risk women Intervention: weekly phone call, daily
phone call, or HUCM system HUCM & Daily Call groups: higher Rx No changes in PTD, birthweight, cx
dilation
Dyson et al NEJM 1998
Risk Factor: Uterine contractions
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NICHD MFMU
The HUAM Prediction Study
Blinded monitoring of Women w/ Risk of PTD Contraction frequency was related to risk of PTD Contractions predicted PTD poorly
Sensitivity = 9.3% for 4 Contractions / hr PPV = 26.7% to predict birth < 35 weeks
Contractions are common in pregnancy Increased frequency in women who will have PTD
is too small to be clinically useful Contractions occur late in process
Iams et al NEJM 2002
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Shortened cervix
Canal Length
Funnel Width
T Y
UVZilanti M, et al: JUM 1995Zilanti M, et al: JUM 1995
Mechanism of Effacement:
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RelativeRelativeRisk ofRisk ofSPTD < 35SPTD < 35wks bywks by% of cervical % of cervical length atlength at24 wks24 wks
Iams et al, NEJM 1996
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Cervical length Follows a Bell curve Risk of PTD increases as cervical length
decreases across entire range of length Cervical changes are same at all GA
Limited studies available to determine effectiveness of Cerclage to prevent PTD in women with PTD
Berghella et al AJOG 1999Althuisius et al AJOG 2000Rust et al AJOG 2001Newman et al AJOG 2002
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Cerclage: Meta-Analysis & Reviews Owen et al AJOG 2003:
“Results are inconclusive”
Odibo et al Ob Gyn Survey 2003: “Trend toward less PTD but not NN mortality”
Bachmann et al Acta Obstet Gynecol 2003
“Significant reduction in PTD < 34 weeks” Belej-Rak et al AJOG 2003r
“No support for cerclage to reduce PTD”
To et al, Lancet 2004; 363:1849-53RCT of 253 women with CL <15 mm: cerclage vs none No difference PTD <33 wks (22% vs 26%, p=0.4)
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Progesterone•Steroid hormone•Progesterone is a small hydrophobic molecule. •Diffuses freely through the plasma membrane of all cells •In target cells, (endometrium)
•becomes tightly bound to a cytoplasmic protein the progesterone receptor
•the complex of receptor-hormone moves into nucleus•binds to a progesterone response element (a specific sequence of DNA in the promoters of certain genes that is needed to turn those genes on/off). The complex of progesterone with its receptor forms a transcription factor.
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Actions of Progesterone on the Myometrium
Decreases conduction of contractions Increases threshold for stimulation Decreases spontaneous activity Decreases number of oxytocin receptors Prevents formation of gap junctions
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Early Trials of Progesterone
43 patients (recur Ab or PTD) Rx: 17P or placebo 41% of placebo group delivered <36 wks 100% of treated group delivered >36 wks
Johnson JWC. NEJM 1975;293:675-680
168 pregnant women in the military Rx: 17P or placebo Low birth weight infants:
7.5% in treated subjects 9.0% in placebo subjects
Hauth JC. Am J Obstet Gynecol 1983;146:187
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Meta-analysis of 17P in pregnancy
5 trials: high risk women with 17P Pooled analysis of results showed:
Reduction in rates of preterm birth Odds ratio 0.50, 95% CI: 0.30-
0.85 Reduction in rates of low birthweight
Odds ratio 0.46, 95% CI: 0.27-0.80
Keirse MJNC. Brit J Obstet Gynecol 1990;97:149
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Prophylactic administration of progesterone by vaginal suppository to reduce the incidence of spontaneous preterm birth in women at increased risk: A randomized placebo-controlled double-blind study
University of Sao Paulo Medical School, Brazil RCT double-blind, placebo controlled 1996-2001 Rx: daily Progesterone (100 mg) vs placebo as
vaginal suppository from 24 – 34 wks
Da Fonseca et alAJOG 2003;188:419-24
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Methods
157 high risk singleton pregnancies, 15(9.5%) lost to follow-up; Prior sPTD (avg 33 wks) Prophylactic cervical cerclage Uterine malformation
Analyzed remaining 142 70 placebo 72 progesterone
Da Fonseca et alAJOG 2003;188:419-24
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Characteristics
Qualifying delivery (wks) 33.3 33.4 Maternal age (yrs) 27.6 26.8 Caucasian 68% 71% Risk Factor
Prior PTD 90% 97% Uterine malformation 5.6% 1.4% Incompetent cervix 4.1% 1.4%
Prog Placebo
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Rates of Preterm Birth
0%
5%
10%
15%
20%
25%
30%
35%
< 37 <34 PTL
P<0.03 P<0.002 NS
Prog
Prog
Prog
Placebo
Placebo
Placebo
Da Fonseca et alAJOG 2003;188:419-24
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Gestational age (wk)
Progesterone
Placebo
P<0.004
UC/hr
Uterine contraction frequency1 hr monitoring/wk
Da Fonseca et alAJOG 2003;188:419-24
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Findings
Progesterone prevented preterm delivery in women
with prior PTD, especially <34 wk reduced the frequency of uterine
contractions
Da Fonseca et alAJOG 2003;188:419-24
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Progesterone trial for the prevention of preterm delivery in high-risk women
Meis et al, NEJM, 2003
NICHD Maternal Fetal Medicine Units Network
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NICHD: MFMU Progesterone Trial
Aim: To establish if weekly progesterone injections in women with prior spontaneous preterm delivery (sPTD) reduces the risk of PTD
Design: double-masked, placebo-controlled trial Eligibility criteria: singleton pregnancy 16-20 wks
with documented previous sPTD Intervention: progesterone or placebo Primary outcome: delivery at < 37 weeks’ Sample: 463 pregnant women
Meis et al, N Engl J Med 2003
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19 Centers enrolled women with:
Documented history of spontaneous preterm birth at 200 to 366 weeks’ gestation in a previous pregnancy
Gestational age at entry of 15-203 weeks confirmed by ultrasound
Singleton gestation, with no major fetal anomalies
Meis et al, N Engl J Med 2003
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Randomization & follow-up
Given a trial injection of the placebo inert oil, and asked to return in 1 week
At next visit,(160 - 206 wks) randomly assigned by a central randomization scheme, to receive injection of 250 mg 17P or a placebo inert oil
The women returned for weekly injections of 17P or placebo until 37 weeks or delivery
Meis et al, N Engl J Med 2003
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Review by Data and Safety Monitoring Committee
Interim analysis was performed after 351 subjects had delivered
Analysis showed positive effect for the primary outcome
Enrollment of new subjects was halted when 463 subjects randomized
Meis et al, N Engl J Med 2003
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Screening & Randomization
2980 women screened
1941 ineligible 1039 eligible
576 refused consent ordeclined after trial injection
463 randomized
310 17-P 163 placebo
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Characteristics
Qualifying delivery (wks) 30.5 31.3 Maternal age (yrs) 26.0 26.5 Married 51% 46% African American 59% 58% Mean BMI 26.9 25.9 Smoking 22% 19%
17-P Placebo
Meis et al, N Engl J Med 2003
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Progesterone: Rates of Preterm Birth
0%
10%
20%
30%
40%
50%
60%
< 37 <35 <32
P<0.0001 P<0.0165 P<0.0180
17 P
17 P
17 P
Placebo
Placebo
Placebo
Meis et al, N Engl J Med 2003
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Progesterone Results: Ethnic Group
0%
10%
20%
30%
40%
50%
60%
70%
African American p=0.0103 Non African American p=0.0044
PlaceboPlacebo
17 P 17 P
P=0.0103 P=0.0044
Meis et al, N Engl J Med 2003
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Effectiveness of Progesterone 5-6 women with a previous sPTB would
need to be treated to prevent one birth <37 weeks
12 women with a previous sPTB birth would need to be treated to prevent one birth <32 weeks Meis et al, N Engl J Med 2003
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Progesterone prevents neonatal complications
0%
2%
4%
6%
8%
10%
12%
14%
16%
neonataldeath
RDS BPD IVH* NEC*
17 P
17 P17 P 17 P
Placebo
Placebo
Placebo
Placebo
Placebo
Meis et al, N Engl J Med 2003
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Compliance and Side Effects
Compliance with the weekly injections was excellent
91.5% of the women received their injections at the scheduled time
Side effects were minor and were similar in the 17P and placebo groups
Meis et al, N Engl J Med 2003
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Progesterone prevents recurrent preterm delivery
Weekly injections of progesterone prevented recurrent preterm birth and improved the neonatal outcome for pregnancies at risk
Effective in preventing very early as well as later preterm birth
Effective in both African American and Non-African American women
Meis et al, N Engl J Med 2003
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ACOG Committee Opinion:Use of Progesterone to Reduce Preterm Birth
Recent studies support progesterone supplementation reduces PTD in select group of women (prior sPTD < 37 wks)
Further studies are needed to evaluate the use of progesterone in patients with other high-risk conditions (multiple gestation, short cervical length, positive FFN)
Recommend restricting progesterone use to prevent PTD for women with prior sPTD
Obstet Gynecol 2003;102:1115-6
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Should women “at risk” be started on progesterone?
PTD etiologies: heterogeneous Limited (if any) ability to predict PTD Many women “at risk”
Demographic characteristics Behavioral factors Obstetric history
Certainly not all will benefit from progesterone
Putting it all together
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Should women “at risk” be started on progesterone?
Prior to da Fonseca and Meis trials – no evidence based research supporting preventative treatment for women to prevent PTD
Overall, limited data available for at risk conditions
There is evidence to support progesterone treatment for women with prior sPTD
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Women “at risk” for PTD Prior spontaneous PTD Multiple gestation Uterine anomaly Cervical incompetence Socioeconomic status Biochemical markers (e.g. FFN) Shortened cervical length Vaginal / cervical infections /inflammation
Medical risk factors: PROMInfections (UTI, vaginal infections, STD) High blood pressure Diabetes Clotting disorders (thrombophilia) Maternal weight (underweight or obesity) Short time period between pregnancies Certain birth defectsVaginal bleeding Lifestyle risk factors:
Late or no prenatal care Smoking Drinking alcohol Using illegal drugs Domestic violence Lack of social support High levels of stress Long working hours Low income
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LBW/Prematurity: Research Needs
Prior spontaneous PTD
• Only one risk factor• Small % of all PTD
SpontaneousIndicated
PPROM
Major initiatives into: -Understanding the cause(s)-Methods of prevention and treatment in pregnant women-Optimal management/treatment of neonates
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Major Research Advances Markers, management and prevention of PTD
Markers: history, FFN, cervical length Management: antenatal steroids, antibiotics &
PPROM Prevention: Progesterone
Management of preterm neonate Inhaled nitric oxide Optimal nutrition for preterm neonate
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Prematurity/LBW Research needs: Major focus:
Prevention Treatment Management of preterm neonates
Mechanisms: Researcher
initiated grants Targeted
requests NIH Multicenter
Networks Education
Mechanism Pathophysiology Genetics Disparity
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NICHD Networks
MFMU Centers MOMs Sites
NICU Network sites >60,000 babies/yrMLS Network sitesMFMU sites >120,000 deliveries/yrMOMs sites
• High risk pregnancies: PTD/LBW prevention and management• Management of the preterm and LBW neonate• Long term outcome of prematurity and LBW
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LBW/Prematurity: Research Needs Investigator initiated grants Trials in NICHD clinical networks
Identify markers Identify treatment Identify preventative therapies Identify optimal management
Long-term follow-up National Children’s Study
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Long term study of environmental influences on children’ health and development
Children’s Health Act, 2000 authorized NICHD Director to collaboratively“…conduct a national longitudinal study of environmental influences
(including physical, chemical, biological, and psychosocial) on children’s health and development”
Follow 100,000 children during prenatal development, birth, childhood into adulthood
Would allow major scientific initiatives to gain understanding, management and treatment of preterm birth
National Children’s Study
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Prematurity Prevention: A Public Health Priority
1 in 8 infants are born preterm (476,000 preterm births / year)
Leading cause of neonatal death Major cause of long-term morbidity Impacts adult health
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LBW/Prematurity Prevention
LBW, Preterm labor and delivery Risk of pregnancy related deaths
and complications related to pregnancy Infant mortality caused by LBW/prematurity
To reduce:
Answers to major research questions Clinical trials and longitudinal data Long term follow-up
Critical need for:
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The goal: healthy children and mothers…