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Maternal & Newborn · Topic 4 of 58

Pregestational Diabetes in Pregnancy

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Maternity · antepartum

Pregestational Diabetes in Pregnancy

Type 1 or type 2 diabetes present before pregnancy. Control at conception prevents birth defects, and insulin needs swing — falling early, rising from about 16 weeks, dropping sharply at birth.

01 · Before conceptionA1C under 6.5% if safe — prevents birth defects
02 · After the placentaInsulin needs drop sharply — watch for lows
03 · The targetsFasting <95, 1 h <140, 2 h <120 mg/dL
01

Why it happens

Insulin needs fall, rise, then drop through pregnancy

First trimester: insulin needs often fall (nausea, less intake)
Fetal glucose use adds to the hypoglycemia risk early on
From about 16 weeks: placental hormones → insulin resistance
Placenta delivered → insulin needs drop sharply

From about 16 weeks the daily dose rises roughly 5% per week through week 36, often doubling the prepregnancy dose. Insulin sensitivity returns to baseline over about 1–2 weeks after birth.

02

What it causes

Risk starts at conception and runs to the newborn

Miscarriage and birth defects (neural tube, heart, caudal regression) poor control at conception
Macrosomia with shoulder dystocia and birth injury
Stillbirth and fetal growth restriction
Preeclampsia and polyhydramnios (excess amniotic fluid)
Newborn hypoglycemia, respiratory distress, hyperbilirubinemia early newborn glucose

Also cesarean birth and postpartum hemorrhage for the client, and hypocalcemia and polycythemia for the newborn. Newborn glucose checks follow the newborn hypoglycemia protocol.

03

Labs & targets

Targets: fasting under 95 · 1 h under 140 · 2 h under 120

Target fasting glucose: under 95 mg/dL
Target after meals: under 140 at 1 h or under 120 at 2 h
Preconception A1C goal: under 6.5% if no hypoglycemia
Dilated eye exam before pregnancy or in the first trimester

Retinopathy can worsen in pregnancy, so eye exams repeat each trimester as indicated. A1C goal during pregnancy is below 6% if safe, relaxed to below 7% to avoid hypoglycemia; A1C runs lower in pregnancy, so glucose checks come first.

04

Red flags

Glucose below 70 mg/dL rule of 15
Nausea, vomiting, abdominal pain or fruity breath DKA? check ketones
DKA can develop at lower glucose levels in pregnancy high stillbirth risk
Hypoglycemia after the placenta delivers expect lower dose

A rapid, significant drop in insulin needs late in pregnancy may signal placental insufficiency — report it. Hypoglycemia awareness can be blunted in pregnancy; risk is highest for type 1 diabetes in the first trimester and postpartum.

05

Treatment

Insulinpreferred drug
insulin

Insulin for type 1 and type 2; metformin users switch to insulin

Needs fall early, rise from about 16 weeks
LabourIV insulin

Continuous IV insulin, hourly glucose, keep 70–120 mg/dL

Subcutaneous insulin is stopped
After birthneeds drop sharply

Expect a lower insulin dose; watch closely for hypoglycemia

Aspirinlowers preeclampsia risk
aspirin

81 mg daily from 12–28 weeks (ideally before 16) to delivery

Folic acidbefore conception

Prenatal vitamin with 400–800 mcg folic acid

Drugs to stop and sick-day tools
ACE inhibitors and ARBs stopped before conception or once pregnant
Glucagon at home for type 1 diabetes, family taught to use it
06

Nursing priorities

Glucose below 70 mg/dL: 15 g fast carbs, recheck in 15 minutes
Nausea, vomiting or abdominal pain: check ketones for DKA
In labour: IV insulin with hourly glucose, keep 70–120 mg/dL
After the placenta delivers: expect a lower dose, watch for lows
Expect early newborn glucose checks per protocol
07

Teach your patient

Plan pregnancy with A1C under 6.5% and folic acid started
Check glucose several times a day, fasting and after meals
Glucose below 70: 15 g fast carbs, recheck in 15 minutes
Type 1: keep glucagon at home; family knows how to use it
Test ketones; report vomiting, abdominal pain or fruity breath
Breastfeeding can cause night lows: check glucose, keep a snack

Breastfeeding is recommended; insulin doses may need lowering while breastfeeding.

Pearl

Insulin needs fall early, climb from about 16 weeks, and drop sharply once the placenta delivers — expect a lower dose after birth and watch closely for hypoglycemia.

Sources · Standards of Care in Diabetes—2026, Section 15: Management of Diabetes in Pregnancy (ADA) · Diabetes Mellitus in Pregnancy (Merck Manual Professional) · Maternal-Newborn Nursing 12.1 Preconception Conditions Affecting Pregnancy (OpenStax) · Gestational Hypertension and Preeclampsia, Practice Bulletin 222 (ACOG) · Treatment of Low Blood Sugar (CDC) · Follow your facility's protocol for intrapartum insulin infusion.

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