🥬 Gestational Diabetes
The placenta makes the mother insulin resistant on purpose. Why the baby is big and then goes hypoglycemic within an hour of birth.
🧬 Why pregnancy causes it
The placenta produces hormones — chiefly human placental lactogen — that deliberately make the mother insulin resistant. The purpose is to keep glucose circulating for the fetus.
If her pancreas cannot keep up with the extra demand, gestational diabetes results.
Because placental hormones peak in the second half of pregnancy, screening is done at 24–28 weeks.
| Risk factor | |
|---|---|
| Obesity, age over 25 | Most common |
| Previous GDM or previous macrosomic baby | Strong predictor |
| Family history of type 2 diabetes | |
| PCOS; previous unexplained stillbirth |
🧪 Screening and control
- 1-hour glucose challenge at 24–28 weeks — no fasting needed. An elevated result leads to…
- 3-hour glucose tolerance test — fasting, then timed draws. Two or more abnormal values confirm the diagnosis
✅ Management, in order
Insulin is the drug of choice — it does not cross the placenta. Insulin needs rise through pregnancy as placental hormones increase, then drop sharply after delivery once the placenta is gone.
Insulin requirements fall dramatically immediately after the placenta is delivered. A woman on insulin needs close glucose monitoring postpartum or she will go hypoglycemic.
👶 The baby — big, then low
Maternal glucose crosses the placenta. Maternal insulin does not.
So the fetus receives excess glucose and its own pancreas ramps up insulin production. Insulin is a growth hormone, which is why the baby grows large.
At birth the glucose supply stops abruptly, but the baby's high insulin level does not - so it drops hypoglycemic within the first hour.
🚨 Newborn priorities
- Check blood glucose within the first hour and regularly after
- Feed early — breast or formula
- Watch for jitteriness, poor feeding, lethargy, weak cry, temperature instability
- Also at risk of hypocalcemia, polycythemia and hyperbilirubinemia
- Examine for birth injury — clavicle, brachial plexus — after a large delivery
🧠 Maternal risks
- Shoulder dystocia and operative delivery, from macrosomia
- Preeclampsia, polyhydramnios
- Recurrence in later pregnancies
- Roughly half develop type 2 diabetes within 10 years — so screening at 6–12 weeks postpartum, and regularly for life, is essential teaching
🎯 NCLEX traps
- Screen at 24–28 weeks
- Insulin, not oral agents — it does not cross the placenta
- Insulin needs rise in pregnancy, crash after delivery
- Big baby, low sugar — check glucose in the first hour
- She needs lifelong diabetes screening afterwards