Infant of the Diabetic Mother (IDM)

Summary
Introduction
Fetal effects of maternal hyperglycaemia
Perinatal complications of diabetes in pregnancy
Neonatal complications of diabetes in pregnancy
Neonatal management
Long Term Complications

Summary

complications in IDMs relate to hyperinsulinism, macrosomia and in utero hypoxia
IDMs (especially those that are macrosomic or growth restricted) are at increased risk of hypoglycaemia - IDMs should be screened for hypoglycaemia and be fed early and frequently
IDMs are at increased risk of Respiratory Distress Syndrome and Persistant Pulmonary Hypertension of the Newborn - watch for respiratory distress and keep well oxygenated
normosomic infants of diet controlled gestational diabetic mothers often require minimal intervention and should be managed in the postnatal ward where possible

Introduction

Approximately 6% of pregnancies are complicated by maternal diabetes mellitus (80% of which are gestational).

Maternal hyperglycaemia can result in fetal hyperglycaemia and then secondary fetal hyperinsulinism. Insulin is the main 'growth hormone' of the fetus and therefore infants of diabetic mothers (IDM) are often macrosomic (> 4,000 g) or large for gestational age (>90th percentile). The problems associated with being IDM relate to the effects of hyperinsulinism and/or macrosomia.

The macrosomia is due to excessive fat deposition, visceral organ hypertrophy (except brain and kidney) and acceleration of body mass accretion. Macrosomic IDMs have higher rates of neonatal morbidity and mortality.

Fetal effects of maternal hyperglycaemia

poor glycaemic control during embryogenesis can result in a 4 to 8 fold increase in congenital malformations, including
- cardiac defects
- CNS defects (including anencephaly and spina bifida)
- genitourinary and limb defects

however, these are not seen with an increased frequency in infants of diabetic fathers, or mothers where gestational diabetes develops after the first trimester

macrosomia leading to increased risk of
- shoulder dystocia
- clavicular fracture
- brachial plexus injury
- facial nerve injury
- cephalhaematoma
- asphyxia
- perinatal and neonatal mortality

However, not all cases of macrosomia can be prevented even with rigid glycaemic control during the 2nd and 3rd trimesters. In fact most macrosomic infants are born to mothers without diabetes (risk factors include morbid maternal obesity, excessive weight gain during pregnancy, multiparity, postmaturity and a previous macrosomic infant).

episodic fetal hypoxia stimulated by episodic maternal hyperglycaemia leads to an outpouring of adrenal catecholamines, which can cause
- hypertension
- cardiac hypertrophy
- stimulation of erythropoietin, leading to polycythaemia and therefore
- +/- hyperviscosity
- increase risk of thrombosis
- hyperbilirubinaemia (increased red cell mass)

Perinatal complications of diabetes in pregnancy

increased perinatal mortality due to
- congenital malformations
- extreme prematurity
- fetal demise
- growth restriction
- intrapartum asphyxia
- RDS
birth injury
- shoulder dystocia
- brachial plexus trauma
over-representation of IUGR (even if mother does not have pre-existing IDDM with small vessel disease) - seen in 20% of IDMs

Neonatal complications of diabetes in pregnancy

polycythaemia and hyperviscosity due to
- increased erythropoiesis secondary to fetal arterial hypoxaemia secondary to hyperinsulinism
- shift in blood from placenta to fetus during hypoxia
hypoglycaemia
- incidence varies from 25-40%
hypocalcaemia (due to functional hypoparathyroidism and hypomagnesaemia)
- occurs in approximately 50% of insulin-dependent diabetics
- suspect if
  - irritability
  - coarse tremours
  - jitters
  - tongue thrusting
  - twitches
  - apnoea
  - seizures
hypomagnesaemia (due to maternal hypomagnesaemia/increased renal losses with glycosuria)
hyperbilirubinaemia due to
- polycythaemia (increased RBC mass)
- increased extravascular haemolysis (bruising, cephalhaematoma)
- delayed oral feeding (increased enterohepatic circulation)
- liver immaturity
hypertrophic and congestive cardiomyopathy
- usually asymptomatic
- usually resolves by 8-12 weeks
respiratory distress due to
- delayed fetal lung maturation (insulin impedes glucocorticoid effect)
- prematurity
- increased incidence of Caesarean section in near term deliveries/complicating 'wet lung syndrome'

Neonatal management

screening for and treatment of hypoglycaemia

abies whose birth weights are between the 10th and 90th percentiles and therefore appropriate for gestational age (i.e. not growth restricted or macrosomic) and/or infants of diabetic mothers not on insulin are at low risk for hypoglycaemia and can be safely screened on the postnatal ward to as to keep mother and baby together

early, frequent oral feeding (preferably breast milk)
glucose infusion (4-6 mg/kg/minute = 60-80 mls/kg/day 10% glucose)
judicious use of glucagon. This can result in rebound neonatal hyperglycaemia and perpetuation of hyperinsulinism. However, it can be very useful in the interim where IV access is not readily achievable and the 'pushing' of feeds is inappropriate
avoid wide swings in infant blood glucose (may perpetuate hyperinsulinism and delay gluconeogenesis)
- the use of 'mini' boluses of glucose for hypoglycaemia (e.g. 2 mls/kg 10% dextrose)
- avoid high calorie formula
measurement of serum calcium and magnesium
adequate oxygenation if baby has HMD (at increased risk of PPHN)

Long Term Complications

obesity - up to 50%
risk of subsequent overt diabetes
- type 1 - father diabetic - 6.1%
- type 1 - mother diabetic - 1.3%
- type 2 - mother diabetic - 50%
- GDM - father diabetic - 7%
- GDM - mother diabetic - 35%
adverse neurodevelopment in 4% of cases (may relate to maternal ketosis)

References

Reece EA, Homko CJ. Infant of the diabetic mother. Seminars in Perinatology. 1994;18:459-69

Suevo DM. The infant of the diabetic mother. Neonatal Network. 1997;16:25-33

Tyrala EE. The infant of the diabetic mother. Obstetrics and Gynaecology Clinics of North America. 1996;23:221-41

Cordero L, London MB. Infant of the diabetic mother. Clinics in Perinatology. 1993;20:635-48

Taeusch HW, Ballard RA (Eds). Avery's Diseases of the Newborn 7th Ed. W.B. Saunders Company, Philadelphia. 1998