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

Contractions start at 10:00, 10:04 and 10:08, and each lasts 60 seconds. How should the nurse describe them?

  1. AEvery 5 minutes, lasting 60 seconds
  2. BEvery 4 minutes, lasting 60 seconds
  3. CEvery 4 minutes, lasting 240 seconds
  4. DEvery 3 minutes, lasting 60 seconds
2.Maternity & obstetric nursingHard

A woman who had a placenta praevia and two previous caesareans is scheduled for a caesarean. The team plans for possible hysterectomy and blood products. Why?

  1. AShe is at high risk of pre-eclampsia only
  2. BShe is at high risk of placenta accreta spectrum
  3. CShe is at high risk of a post-term birth
  4. DShe is at high risk of gestational diabetes
3.Dosage calculationsMedium
024681010 mL

A child weighing 20 kg is prescribed 5 mg/kg of a drug. The stock solution contains 50 mg/mL. Draw up the dose: what volume V do you give?

20 kg5 mg/kg50 mg/mL
V = mL
4.Dosage calculationsHard
20%stockwater = ? mL

You must prepare 100 mL of a 5% (w/v) solution from a 20% (w/v) stock solution. How much water W must be added to the stock?

C₁ = 20%C₂ = 5%V₂ = 100 mL
W = mL
5.IV infusion ratesMedium
1500 mL20 gtt/mL12 h? gtt/min

Infuse 1500 mL over 12 hours with a giving set of 20 gtt/mL. Find the drip rate R in drops per minute. Round to the nearest whole number.

1500 mL12 h20 gtt/mL
R = gtt/min
6.IV infusion ratesHard
100 mg250 mL15 mL/h? mg/h

A bag contains 100 mg of a drug in 250 mL and runs at 15 mL/h. How many milligrams per hour D does the patient receive?

100 mg/250 mL15 mL/h
D = mg/h

3Solutions

1.Maternity & obstetric nursing

Answer: B · Every 4 minutes, lasting 60 seconds

Why this is the answer

Frequency is measured from the start of one contraction to the start of the next (4 minutes), and duration from the start to the end of the same contraction (60 seconds). The 3 minutes between contractions is the resting interval.

Answer

B · Every 4 minutes, lasting 60 seconds
2.Maternity & obstetric nursing

Answer: B · She is at high risk of placenta accreta spectrum

Why this is the answer

A placenta praevia overlying a previous caesarean scar greatly raises the risk of an abnormally adherent placenta. This can cause massive haemorrhage, so delivery is planned in a unit with blood bank support.

Answer

B · She is at high risk of placenta accreta spectrum
3.Dosage calculations

Answer: V = 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 = 5·20 = 100 mg

Volume

V = 100/50 = 2 mL

On the syringe

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

Answer

V = 2 mL
4.Dosage calculations

Answer: W = 75 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 = 5·100/20 = 25 mL

Water to add

W = 100 − 25 = 75 mL

Answer

W = 75 mL
5.IV infusion rates

Answer: R = 42 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.

Time in minutes

12·60 = 720 min

Drip rate

R = 1500·20/720 = 41.67 ≈ 42 gtt/min

Answer

R = 42 gtt/min

At the bedside you round to the nearest whole drop: 42 gtt/min.

6.IV infusion rates

Answer: D = 6 mg/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.

Concentration

100/250 = 0.4 mg/mL

Dose rate

D = 0.4·15 = 6 mg/h

Answer

D = 6 mg/h

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