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

A pregnant woman asks why she needs a whooping cough (pertussis) vaccine in pregnancy. Which answer is correct?

  1. AIt protects her from pre-eclampsia
  2. BIt is a live vaccine that gives the baby lifelong immunity to whooping cough
  3. CIt prevents the baby from developing rubella
  4. DHer antibodies cross the placenta and protect the newborn
2.Maternity & obstetric nursingHard

At 18 weeks, a woman's maternal serum alpha-fetoprotein is well above the normal range for her dates. Which condition does this result most suggest?

  1. AAn open neural tube defect
  2. BDown syndrome (trisomy 21)
  3. CPre-eclampsia
  4. DGestational diabetes
3.Dosage calculationsMedium
18 kg15 mg/kg/day2× per dayD = ? mg

A patient weighs 18 kg. The prescribed dose is 15 mg/kg per day, given in 2 equal doses. How many milligrams D are given per dose?

18 kg15 mg/kg/day2× per day
D = mg
4.Dosage calculationsHard
10%stockV₁ = ? mL

You must prepare 500 mL of a 0.5% (w/v) solution from a 10% (w/v) stock solution. What volume of stock V₁ do you need?

C₁ = 10%C₂ = 0.5%V₂ = 500 mL
V₁ = mL
5.IV infusion ratesMedium
10 gtt/mL120 mL/h? gtt/min

An infusion is ordered at 120 mL/h, but no pump is available. It runs by gravity through a giving set of 10 gtt/mL. Find the drip rate R in drops per minute.

120 mL/h10 gtt/mL
R = gtt/min
6.IV infusion ratesHard
400 mL15 gtt/mL40 gtt/mint = ? h

A drip runs at 40 gtt/min through a set of 15 gtt/mL. There are 400 mL left in the bag. How many hours t until it is empty?

40 gtt/min15 gtt/mL400 mL
t = h

3Solutions

1.Maternity & obstetric nursing

Answer: D · Her antibodies cross the placenta and protect the newborn

Why this is the answer

Maternal pertussis antibodies cross the placenta and protect the newborn before it can be immunised. Whooping cough can be fatal in young infants.

Answer

D · Her antibodies cross the placenta and protect the newborn
2.Maternity & obstetric nursing

Answer: A · An open neural tube defect

Why this is the answer

High AFP is linked to open neural tube defects and abdominal wall defects, but also to wrong dates or twins. Low AFP is associated with trisomy 21. A detailed ultrasound is the next step.

Answer

A · An open neural tube defect
3.Dosage calculations

Answer: D = 135 mg

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.

Total per day

15·18 = 270 mg

Per dose

D = 270/2 = 135 mg

Answer

D = 135 mg
4.Dosage calculations

Answer: V₁ = 25 mL

Solution strengths: a percentage strength is grams per 100 mL, so 1% = 1 g/100 mL = 10 mg/mL. A ratio strength 1:1000 means 1 g in 1000 mL = 1 mg/mL; 1:10 000 is 0.1 mg/mL. For a dilution the amount of drug stays the same: C₁·V₁ = C₂·V₂.

Volume of stock

V₁ = 0.5·500/10 = 25 mL

Answer

V₁ = 25 mL
5.IV infusion rates

Answer: R = 20 gtt/min

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.

Millilitres per minute

120/60 = 2 mL/min

Drip rate

R = 2·10 = 20 gtt/min

Answer

R = 20 gtt/min
6.IV infusion rates

Answer: t = 2.5 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

40·60/15 = 160 mL/h

Time left

t = 400/160 = 2.5 h

Answer

t = 2.5 h

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