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OG12.11,OG16.4 | Intrauterine Growth Retardation — SDL Guide (Part 2)

Management Principles and Timing of Delivery

The management of IUGR requires individualised decision-making that balances two competing risks: the risk of ongoing intrauterine hypoxia and potential fetal death if the pregnancy continues, against the risk of iatrogenic prematurity if delivery is timed too early. No single intervention can treat the underlying placental pathology; the mainstay of management is meticulous fetal surveillance to identify the optimal window for delivery before irreversible fetal compromise.

Outpatient versus inpatient management depends on the severity of the Doppler findings. A fetus with normal UA Doppler but confirmed IUGR (EFW <10th centile) may be monitored with fortnightly biometry and twice-weekly Doppler in an outpatient setting. AEDF, abnormal MCA/CPR, or BPP compromise warrants admission for closer and more frequent monitoring.

Corticosteroids (betamethasone 12 mg IM 24 hours apart × 2 doses, or dexamethasone 6 mg IM 6-hourly × 4 doses) are administered when delivery is anticipated before 34 weeks, ideally at least 24 hours before delivery, to accelerate fetal lung maturation and reduce the risk of respiratory distress syndrome, intraventricular haemorrhage, and necrotising enterocolitis. A rescue (repeat) course may be given if the first course was given before 34 weeks and delivery has not occurred within 7 days.

Magnesium sulphate (MgSO4) for neuroprotection: when preterm delivery is anticipated before 32 weeks (some guidelines extend to <34 weeks), MgSO4 is administered to reduce the risk of cerebral palsy. The RCOG regimen is a loading dose of 4 g IV over 20–30 minutes followed by 1 g/h maintenance infusion until delivery (or for a maximum of 24 hours). This is distinct from the eclampsia regimen (Pritchard or Zuspan) — the neuroprotection indication uses the same drug but at lower maintenance doses and for a different purpose.

Delivery timing is guided by gestational age, Doppler findings, and the TRUFFLE trial evidence:
• Term or near-term IUGR (≥37 weeks): deliver by 37–38+6 weeks in mild-to-moderate IUGR; by 37 weeks if UA Doppler is abnormal or CPR is impaired.
• Severe early-onset IUGR (<34 weeks) with AEDF: admit; twice-weekly ductus venosus Doppler + BPP; deliver when DV becomes abnormal (PI >95th centile), DV a-wave becomes absent or reversed, BPP falls to ≤4, or there is CTG evidence of short-term variability loss.
• REDF in the umbilical artery: deliver by 34 weeks; earlier if DV or BPP becomes abnormal. Below 28 weeks, REDF represents an extremely difficult decision — parental counselling about prognosis is mandatory.
• Ductus venosus absent/reversed a-wave: deliver regardless of gestational age if the fetus is viable, after administration of corticosteroids if time allows.

The TRUFFLE trial enrolled 503 early-onset preterm IUGR fetuses (26–32 weeks) and randomised delivery timing to three triggers: CTG short-term variability, DV PI >95th centile, or DV a-wave absent/reversed. The primary outcome was survival without neurodevelopmental impairment at 2 years. The DV a-wave trigger arm achieved the best balance of outcome, forming the basis of current evidence-based practice.

Mode of delivery: there is no absolute rule. Vaginal delivery with continuous electronic fetal monitoring is appropriate in the majority of IUGR fetuses without other obstetric indications for caesarean. However, a fetus with severe IUGR and REDF or DV abnormality has limited physiological reserve and may not tolerate the stress of labour — a decision for caesarean section should be made with the obstetric team and documented. Intrapartum CTG must be interpreted with heightened vigilance; a non-reassuring CTG in a growth-restricted fetus requires expedited delivery.

Neonatal preparation: a neonatologist must be present at delivery; the neonatal team should be briefed pre-delivery. Expected neonatal complications include hypothermia, hypoglycaemia, polycythaemia, respiratory distress syndrome (if preterm), necrotising enterocolitis, and neurodevelopmental delay.

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IUGR Management by Doppler Severity and Gestational Age

Prevention, Counselling, and Long-Term Implications

While the underlying placental pathology in most cases of IUGR cannot be reversed once established, several preventive and modifiable strategies can reduce recurrence risk and attenuate severity.

Low-dose aspirin (75–150 mg at night) is the most evidence-based pharmacological intervention for prevention of placenta-mediated IUGR. Aspirin inhibits thromboxane synthesis preferentially, reducing platelet-mediated vasoconstriction and placental microthrombus formation. It should be commenced before 16 weeks of gestation (ideally by 12 weeks) in women with high-risk factors: previous pre-eclampsia or IUGR, chronic hypertension, diabetes with vasculopathy, antiphospholipid syndrome, or ≥3 moderate-risk factors (BMI >35, age >40, nulliparity, multiple pregnancy, family history of pre-eclampsia). The ASPRE trial demonstrated that aspirin from 11–14 weeks in women identified as high-risk by first-trimester combined screening reduced preterm pre-eclampsia and IUGR by approximately 62%.

Other preventive measures include optimisation of maternal nutrition (adequate protein and micronutrients — iron, folate, calcium supplementation per national guidelines), smoking cessation (smoking is an independent, strong, dose-dependent cause of IUGR — women who quit before 15 weeks have outcomes approaching non-smokers), treatment of underlying hypertension and thrombophilias, and haematological management of severe anaemia before conception.

Counselling should address: (a) the prognosis for the current pregnancy, including the surveillance plan and what findings would trigger hospitalisation or delivery; (b) the recurrence risk — approximately 20–25% in the next pregnancy, higher if caused by thrombophilia or APS; (c) the plan for pre-conceptional optimisation in future pregnancies (aspirin, specialist review); and (d) the long-term implications for the child. Neonates who were growth-restricted are at elevated risk for learning difficulties, attention deficit disorders, and impaired neurodevelopment, particularly if born preterm.

Barker hypothesis (developmental origins of health and disease): one of the most important long-term implications of IUGR is the programming effect on fetal metabolism. Barker and colleagues demonstrated that undernutrition during critical windows of fetal development permanently alters gene expression and metabolic set-points (epigenetic programming), predisposing the individual to coronary artery disease, hypertension, type 2 diabetes, and metabolic syndrome in adult life — even when nutrition becomes adequate after birth. This relationship was first observed in populations exposed to famine during the Dutch Hunger Winter (1944–45). Counselling should note that although the child's long-term risk is elevated, a healthy postnatal environment — adequate nutrition without excess, physical activity, and no smoking — can substantially attenuate this programmed risk.