Meticulous control around conception 'malformation rates. Tell all diabetics about preconception services; they must know before pregnancy. Preconception change to insulin may help control. Treat retinopathy pre-pregnancy. Up to 20% may develop proliferative retinopathy so screen twice in pregnancy. If severe renal involvement; avoid pregnancy. DM may be pre-existing or appear in pregnancy; glycosuria unrelated to DM is common (glomerular filtration ' and tubular glucose reabsorption'). Non-diabetic blood glucose levels in pregnancy are constant (3.5 4.5mmol/L) except after meals. Fetal glycaemia follows maternal, but compensatory fetal hyper-insulinaemia promotes fetal growth.
Complications
Maternal
Hydramnios (25% ?due to fetal polyuria), preterm labour (17% associated with hydramnios). Stillbirth near term was common.
Fetal
Malformation rates '3 4-fold. Sacral agenesis, almost exclusive to diabetic offspring, is rare (CNS & CVS malformations are much commoner). Babies may be macrosomic (too large) or sometimes growth restricted.
Neonatal risks
Hypoglycaemia, Ca2+', Mg2+', and RDS (p 118). They may be polycythaemic (29%) so more neonatal jaundice.
Antenatal care
Review in joint clinic with diabetologist. Confirm gestation with early ultrasound. Detailed abnormality scan at 19 20 weeks. Fetal echo at 22 weeks if early control poor. Educate about benefits of normoglycaemia and home glucose monitoring: regular postprandial monitoring does prevent harm to the baby. Insulin needs increase by 50 100% as pregnancy progresses so review regularly. Aim for fasting level <5.5mmol/L; 1h post-prandial level <7.5mmol/L. Give glucagon kit and ensure partner knows how to use it. Admit if adequate control impossible to achieve at home. Oral hypoglycaemics are currently avoided though glyburide does not cross placenta and may be safe.16
Monitor fetal growth and wellbeing by ultrasound and cardiotocography.
Delivery
Timing takes into account control of diabetes, any pre-eclampsia, maturity and size of the baby, and with attention to fetal wellbeing. Delivery before 38 weeks may result in neonatal respiratory distress. Deliver the baby where there are good neonatal facilities. Traditionally, delivery was at 36 38 weeks to avoid stillbirth; but with close supervision pregnancies may go nearer to (but not beyond) term.
In labour
Avoid acidosis and monitor the fetus (p 44). Avoid maternal hyperglycaemia (causes fetal hypoglycaemia). Monitor glucose; prevent hyperglycaemia with extra insulin (may need 5U/h) if β-sympathomimetics or glucocorticoids are used in preterm labour. Aim for vaginal delivery with a labour of <12h. Beware shoulder dystocia with macrosomic babies. With elective delivery, give normal insulin the evening before induction. During labour give 1L of 5 10% glucose/8h IVI with 1 2U insulin/h via a pump. Aim for a blood glucose of 4.5 5.5mmol/L (check hourly). Insulin needs fall as labour progresses and immediately postpartum. Stop infusions at delivery. Return to pre-pregnancy regimen. Do a caesarean section if labour is prolonged. Clamp cord early (as polycythaemia risk).
Postnatal
- Encourage breast feeding (oral hypoglycaemics contraindicated).
- Encourage pre-pregnancy counselling before next pregnancy (p 2) to transfer to insulin.
- Do a postpartum glucose tolerance test at 6 weeks.
Gestational diabetes
(OGTT glucose ‰ 7.8, OHCM p 294) Incidence: 3%.17 50% get full DM, so give lifelong dietary advice & follow-up.18 Equations exist for giving risk of post-pregnancy DM from pre-pregnancy BMI (p 530), fasting plasma glucose, and months since delivery.19 Other risk factors: age >30yrs; mothers who themselves have had low birth weights or IUGR (p 52); 1st-degree relative with DM; unexplained stillbirth;20 gestational DM before 27 weeks (or if needing insulin).21 22 [n=1636]
™£ Exercise, a good diet, and no smoking all help lower this risk.
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