Maternity Nursing: cram pack

Formula sheets, the key method steps for every topic and 6 practice problems, with full solutions at the back.

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1Formulas and methods

Maternity & obstetric nursing

Method

  1. Place the woman in time: weeks of pregnancy, stage of labour or day after birth, and decide what is normal at that point.
  2. Look for the patient in danger: the mother, the fetus or the newborn, or more than one of them.
  3. Link the finding to its cause: VEAL CHOP for decelerations, the four Ts for bleeding, BUBBLE-HE after birth.
  4. Choose the action that improves blood flow and oxygen first (side-lying, stopping oxytocin, fundal massage), then escalate.

Dosage calculations

Dose from strength
volume = dose / strength
Weight-based dose
dose = mg/kg × body weight
Tablets
number = dose / tablet strength
Units
1 g = 1000 mg, 1 mg = 1000 mcg

Method

  1. Convert the ordered dose and the stock strength to the same unit.
  2. Use desired over have times quantity: (D/H) × Q.
  3. For weight-based doses, multiply by the weight in kg first, then divide the daily dose by the number of doses.
  4. Estimate first and check that the answer is reasonable.

IV infusion rates

Pump rate
mL/h = volume (mL)/time (h)
Drip rate
drops/min = volume (mL) × drop factor / time (min)
Infusion time
time (h) = volume (mL)/rate (mL/h)

Method

  1. Pump rate in mL/h: volume divided by time in hours.
  2. Drip rate in drops/min: volume × drop factor divided by time in minutes.
  3. For time remaining: volume left divided by the rate.
  4. Round as the question or the equipment requires.

2Practice problems

1.Maternity & obstetric nursingMedium

Which test estimates how much fetal blood has entered the mother's circulation, to guide the dose of anti-D?

  1. AKleihauer–Betke test
  2. BGlucose tolerance test
  3. CDirect Coombs test on the baby
  4. DNitrazine test
2.Maternity & obstetric nursingHard

After treatment for a molar pregnancy, what is the most important teaching point?

  1. AAvoid all physical activity for 6 months
  2. BAttend serial hCG checks and use reliable contraception during follow-up
  3. CNo further follow-up is needed once the uterus is empty
  4. DTry to conceive again as soon as possible to reduce recurrence
3.Dosage calculationsMedium
024681010 mL

A child weighing 15 kg is prescribed 4 mg/kg of a drug. The stock solution contains 50 mg/mL. Draw up the dose: what volume V do you give?

15 kg4 mg/kg50 mg/mL
V = mL
4.Dosage calculationsHard
125 mg/5 mLV = ? mL

A child weighing 24 kg is prescribed 15 mg/kg per dose of an oral suspension that contains 125 mg in 5 mL. What volume V do you give?

24 kg15 mg/kg125 mg/5 mL
V = mL
5.IV infusion ratesMedium
V = ?20 gtt/mL40 gtt/min2 h

A drip runs at 40 gtt/min through a set of 20 gtt/mL. How many millilitres V does the patient receive in 2 hours?

40 gtt/min20 gtt/mL2 h
V = mL
6.IV infusion ratesHard
450 mL20 gtt/mL28 gtt/mint = ? h

A drip runs at 28 gtt/min through a set of 20 gtt/mL. There are 450 mL left in the bag. How many hours t until it is empty? Round to one decimal place.

28 gtt/min20 gtt/mL450 mL
t = h

3Solutions

1.Maternity & obstetric nursing

Answer: A · Kleihauer–Betke test

Why this is the answer

The Kleihauer–Betke test (or flow cytometry) measures fetal red cells in maternal blood after a sensitising event such as trauma or birth. The result guides whether extra anti-D is needed.

Answer

A · Kleihauer–Betke test
2.Maternity & obstetric nursing

Answer: B · Attend serial hCG checks and use reliable contraception during follow-up

Why this is the answer

hCG is followed until it is undetectable because persistent trophoblastic disease or choriocarcinoma can develop. A new pregnancy would raise hCG and hide this, so reliable contraception is advised during follow-up.

Answer

B · Attend serial hCG checks and use reliable contraception during follow-up
3.Dosage calculations

Answer: V = 1.2 mL

Drawing up a dose: volume = (prescribed dose/stock strength) × stock volume. Convert to the same units first, then check that the volume fits the syringe and lands on one of its graduations.

Dose from body weight

D = 4·15 = 60 mg

Volume

V = 60/50 = 1.2 mL

On the syringe

On this 10 mL syringe every small line is 0.2 mL.

Answer

V = 1.2 mL
4.Dosage calculations

Answer: V = 14.4 mL

Dose calculation: the amount to give equals what is prescribed divided by what you have, times the quantity it comes in: amount = (desired dose/stock strength) × stock volume. Always keep the units the same (convert g to mg, mg to mcg first) and check that the answer is sensible.

Dose from weight

15·24 = 360 mg

Volume

V = (360/125)·5 = 14.4 mL

Answer

V = 14.4 mL
5.IV infusion rates

Answer: V = 240 mL

Infusion rates: a pump is set in mL/h = volume/time in hours. A gravity drip is counted in drops per minute: gtt/min = volume (mL) × drop factor (gtt/mL)/time (min). The drop factor is printed on the tubing package: macrodrip sets deliver 10, 15 or 20 gtt/mL (blood sets often 10 gtt/mL in the US, 15 in the UK) and microdrip sets 60 gtt/mL. Always use the drop factor the question or package gives.

Rate in mL/h

40·60/20 = 120 mL/h

Volume

V = 120·2 = 240 mL

Answer

V = 240 mL
6.IV infusion rates

Answer: t = 5.4 h

Infusion rates: a pump is set in mL/h = volume/time in hours. A gravity drip is counted in drops per minute: gtt/min = volume (mL) × drop factor (gtt/mL)/time (min). The drop factor is printed on the tubing package: macrodrip sets deliver 10, 15 or 20 gtt/mL (blood sets often 10 gtt/mL in the US, 15 in the UK) and microdrip sets 60 gtt/mL. Always use the drop factor the question or package gives.

Rate in mL/h

28·60/20 = 84 mL/h

Time left

t = 450/84 = 5.357 ≈ 5.4 h

Answer

t = 5.4 h

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