Premature birth

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Premature Birth (Preterm Birth)

Definition

Premature (preterm) birth is defined as delivery before 37 completed weeks of gestation. It affects nearly 1 in 10 newborns worldwide and is a major cause of perinatal morbidity and mortality (Management of Pregnancy, p. 82).

Classification by Gestational Age

Category	Gestational Age
Extremely preterm	< 28 weeks
Very preterm	28–31 weeks
Moderate preterm	32–33 weeks
Late preterm	34–36 weeks

Causes & Risk Factors

About 50% of preterm births are related to spontaneous preterm labor; the rest result from medically indicated early delivery or premature rupture of membranes (PROM).

Strongest predictors:

Prior history of spontaneous preterm birth (single strongest risk factor)
Prior preterm pre-labor rupture of membranes (PPROM)
Multiple gestation (twins, triplets, etc.)
Short cervical length (< 25 mm on ultrasound)

Other risk factors:

Uterine/cervical anomalies
Infections (chorioamnionitis, bacterial vaginosis, UTI)
Placenta previa or placental abruption
Polyhydramnios
Maternal age extremes (< 17 or > 35)
Low socioeconomic status, smoking, substance use
Psychological distress / chronic stress
Inadequate prenatal care

Preterm Infant: NICU Care

Preterm neonate in NICU incubator with medical support

A preterm neonate in a NICU isolette receiving IV infusions and monitoring — illustrating the intensive supportive care required for premature infants.

Premature infants are cared for in the Neonatal Intensive Care Unit (NICU) in isolettes (incubators) that provide:

Thermoregulation (preterm infants cannot maintain body temperature)
Precise IV fluid/medication delivery via infusion pumps
Continuous cardiorespiratory monitoring
Umbilical catheters for vascular access

Complications of Prematurity

Complications vary significantly by degree of prematurity:

Respiratory

Respiratory Distress Syndrome (RDS) — surfactant deficiency; most common cause of early death
Bronchopulmonary dysplasia (BPD) / chronic lung disease
Apnea of prematurity

Neurological

Intraventricular hemorrhage (IVH)
Periventricular leukomalacia (PVL)
Long-term risk of cerebral palsy, cognitive delays

Cardiovascular

Patent ductus arteriosus (PDA)
Hypotension

Gastrointestinal

Necrotizing enterocolitis (NEC) — serious bowel inflammation/necrosis
Feeding intolerance, poor sucking reflex

Infectious

Sepsis (common pathogens: CoNS, E. coli, Group B Streptococcus, Candida spp.)
Higher susceptibility due to immature immune system

Metabolic

Hypoglycemia, hypocalcemia
Jaundice (hyperbilirubinemia)

Ophthalmologic

Retinopathy of prematurity (ROP)

Prevention

Risk assessment should occur at the first prenatal visit for all patients (Management of Pregnancy, p. 82).

Intervention	Indication
Vaginal progesterone	Short cervix (< 25 mm) on mid-trimester ultrasound
17-hydroxyprogesterone caproate (17-OHPC)	History of prior spontaneous preterm birth (singleton pregnancy)
Cervical cerclage	Cervical insufficiency + prior preterm birth or short cervix
Antenatal corticosteroids (betamethasone)	24–34 weeks at risk of delivery within 7 days — accelerates fetal lung maturation
Magnesium sulfate	< 32 weeks — neuroprotection against cerebral palsy
Antibiotics	GBS prophylaxis in labor; treat infections promptly

Management of Preterm Labor

Tocolytics — delay delivery to allow corticosteroid administration (e.g., nifedipine, indomethacin, atosiban); not for long-term use
Antenatal corticosteroids — most important intervention (betamethasone IM × 2 doses)
Antibiotics — for PPROM to prolong latency and reduce neonatal infection
Delivery planning — at an appropriate-level facility with NICU capability
Mental health support — women with high-risk status should be offered mental health treatment (Management of Pregnancy, p. 82)

Prognosis

Outcomes improve significantly with each additional week of gestation:

< 23 weeks: survival rare; outcomes very poor
23–24 weeks: survival ~50%; high morbidity
28–31 weeks: ~90%+ survival with NICU care
34–36 weeks (late preterm): generally good outcomes but higher risk than term for respiratory issues, feeding problems, and readmission

The syndrome of intrauterine development of foetus

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Syndrome of Intrauterine Fetal Development

This topic covers two interrelated subjects: (1) normal intrauterine fetal development — the sequential stages from conception to term — and (2) intrauterine growth restriction (IUGR) — the pathological syndrome where fetal growth deviates from expected parameters.

Part 1: Normal Intrauterine Development

Intrauterine development spans approximately 40 weeks (280 days) from the last menstrual period and is divided into three major periods:

1. Pre-embryonic Period (Weeks 1–2)

Fertilization → zygote formation
Cleavage, blastocyst formation, implantation into the uterine wall
Formation of the bilaminar disc (epiblast + hypoblast)

2. Embryonic Period (Weeks 3–8)

This is the critical period of organogenesis — the embryo is most vulnerable to teratogens.

Week	Key Developments
3–4	Gastrulation (trilaminar disc); neural tube formation; heart begins beating
5–6	Limb buds appear; face begins forming; liver, lungs, pancreas rudiments
7–8	Fingers/toes distinguishable; all major organs established; embryo → fetus transition

3. Fetal Period (Weeks 9–40)

Characterized by rapid growth and maturation of established organs.

Trimester	Weeks	Major Milestones
1st	1–13	Organogenesis complete by week 8; sex differentiation (week 9–12); kidneys begin urine production
2nd	14–27	Rapid growth; fetal movements felt (~18–20 wks); viability threshold (~23–24 wks); surfactant production begins (~24 wks)
3rd	28–40	Lung maturation; brain myelination; fat deposition; CNS refinement; weight gain (~200 g/week)

Hormonal Orchestration of Development

Fetal development is tightly regulated by an interplay of hormones. Key axes include:

HCG — sustains corpus luteum in early pregnancy
Placental estrogen & progesterone — maintain uterine quiescence and support organogenesis
Fetal thyroid hormones — critical for brain and skeletal maturation
IGF-1 and IGF-2 — primary drivers of intrauterine somatic growth
Cortisol — surges before term; triggers lung surfactant production and organ maturation

Part 2: Intrauterine Growth Restriction (IUGR)

Definition

IUGR (also called fetal growth restriction, FGR) is a condition in which the fetus fails to achieve its genetically determined growth potential. Defined as estimated fetal weight (EFW) or abdominal circumference (AC) < 10th percentile for gestational age.

Obstetric ultrasound series showing gestational sac, embryo development, nuchal translucency, and Doppler flow assessment

Serial obstetric ultrasound images illustrating embryonic development, crown-rump length measurement, nuchal translucency screening (NT = 0.20 cm), and Doppler vascular assessment — key tools in monitoring intrauterine development and detecting IUGR.

Classification

Type	Description	Cause
Symmetric IUGR	All organs equally small; head circumference reduced	Early insult (chromosomal anomaly, infection); affects ~20–30%
Asymmetric IUGR	Head-sparing; abdomen disproportionately small	Late uteroplacental insufficiency; affects ~70–80%

Etiology / Causes

Maternal (most common):

Hypertensive disorders (preeclampsia, chronic hypertension)
Diabetes mellitus with vascular disease
Smoking, alcohol, substance abuse (cocaine, opioids)
Malnutrition / severe anemia
Thrombophilias (antiphospholipid syndrome)
Chronic renal or cardiac disease
Smoking — directly reduces fetal growth (Harrison's, p. 11110)

Placental:

Placental insufficiency (most common cause of asymmetric IUGR)
Placenta previa, abruption
Umbilical cord abnormalities

Fetal:

Chromosomal anomalies (trisomy 13, 18, 21)
Congenital malformations
Multiple gestation
Congenital infections — TORCH: Toxoplasmosis, Rubella, CMV, Herpes/HIV

Diagnosis

Accurate gestational dating — fundal height measurement (< 10th percentile for GA)
Ultrasound biometry — key parameters:
- Abdominal circumference (AC) — most sensitive single parameter
- Estimated fetal weight (EFW)
- Head circumference (HC) and femur length (FL)
Doppler studies — assess uteroplacental blood flow:
- Umbilical artery (UA) Doppler — absent/reversed end-diastolic flow = severe compromise
- Middle cerebral artery (MCA) — "brain-sparing" pattern
- Ductus venosus (DV) — waveform abnormalities indicate imminent fetal compromise
Amniotic fluid assessment — oligohydramnios common in IUGR
Biophysical profile (BPP)
Karyotyping — if structural anomalies present
TORCH serology

Management

Step	Action
Identify & treat cause	Optimize maternal disease; stop smoking/substances
Increased surveillance	Serial growth scans every 2–4 weeks; Doppler twice weekly in severe IUGR
Antenatal corticosteroids	Betamethasone if preterm delivery anticipated (< 34 weeks)
Magnesium sulfate	Neuroprotection if delivery < 32 weeks
Timing of delivery	Balance risk of prematurity vs. fetal compromise (individualized)
Delivery	Vaginal delivery if stable; cesarean section if fetal compromise detected

Delivery timing guidelines:

Absent UA end-diastolic flow → deliver at 34 weeks
Reversed UA flow / abnormal DV → deliver at 32 weeks or earlier
Severe IUGR < 32 weeks → tertiary center with NICU

Complications

In utero:

Fetal hypoxia and acidosis
Stillbirth

Neonatal:

Hypoglycemia, hypothermia, polycythemia
Respiratory distress
Necrotizing enterocolitis (NEC)
Increased susceptibility to sepsis

Long-term (Barker Hypothesis / Developmental Origins of Health and Disease):

Cardiovascular disease (hypertension, coronary artery disease)
Type 2 diabetes mellitus
Metabolic syndrome
Neurodevelopmental delays

Prognosis

Prognosis depends on gestational age at onset, severity of growth restriction, and underlying etiology. Early-onset IUGR (< 32 weeks) carries the worst prognosis. With modern Doppler surveillance and timely delivery, perinatal mortality has been significantly reduced.

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