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 woman at 28 weeks is Rh-negative and has a positive antibody screen for anti-D. What does this mean?

  1. AShe needs a double dose of anti-D immunoglobulin
  2. BShe is sensitised; the fetus is watched for anaemia
  3. CThe result is normal and needs no further action
  4. DHer baby is definitely Rh-negative
2.Maternity & obstetric nursingHard

A woman at 30 weeks reports a sudden gush of clear fluid from the vagina without contractions. What is the priority nursing action?

  1. AAdvise a warm bath to see whether the leaking stops
  2. BPerform a digital vaginal examination to check dilation
  3. CReassure her that it is urine and send her home
  4. DAssess the fetal heart rate and check the fluid, and avoid a digital examination
3.Dosage calculationsMedium
40 kgBSA = 1.16 m²75 mg/m²D = ? mg

A patient weighing 40 kg has a body surface area of 1.16 m². The prescription is 75 mg/m². Find the dose D in mg.

40 kgBSA = 1.16 m²75 mg/m²
D = mg
4.Dosage calculationsHard
250 mg/5 mLV = ? mL

A patient weighs 50.6 lb. The prescription is 0.5 mg/kg as a single dose, and the stock contains 250 mg in 5 mL. Using 1 kg = 2.2 lb, what volume V do you give?

50.6 lb0.5 mg/kg250 mg/5 mL1 kg = 2.2 lb
V = mL
5.IV infusion ratesMedium
1450 mLleft? mL/h10 h left

1500 mL was ordered over 12 hours. After 2 hours you find that 1450 mL is still in the bag, and the order must still finish on time. To what rate R in mL/h must the pump be reset?

1500 mL / 12 hafter 2 h: 1450 mL
R = mL/h
6.IV infusion ratesHard
600 mL20 gtt/mL30 gtt/mint = ? h

A drip runs at 30 gtt/min through a set of 20 gtt/mL. There are 600 mL left in the bag. How many hours t until it is empty? Round to one decimal place.

30 gtt/min20 gtt/mL600 mL
t = h

3Solutions

1.Maternity & obstetric nursing

Answer: B · She is sensitised; the fetus is watched for anaemia

Why this is the answer

If antibodies are already present, anti-D prophylaxis is of no use. Antibody levels are followed and the fetus is monitored for anaemia, often with Doppler of the middle cerebral artery.

Answer

B · She is sensitised; the fetus is watched for anaemia
2.Maternity & obstetric nursing

Answer: D · Assess the fetal heart rate and check the fluid, and avoid a digital examination

Why this is the answer

Preterm prelabour rupture of membranes is suspected. The nurse assesses the fetal heart rate and the fluid's colour, amount and odour, and avoids digital examinations, which raise the risk of infection.

Answer

D · Assess the fetal heart rate and check the fluid, and avoid a digital examination
3.Dosage calculations

Answer: D = 87 mg

Body-surface-area dosing: many cytotoxic and some paediatric doses are prescribed per square metre of body surface area: dose (mg) = dose per m² × BSA (m²). The Mosteller formula estimates BSA = √(height (cm) × weight (kg)/3600).

Dose

D = 75·1.16 = 87 mg

Answer

D = 87 mg
4.Dosage calculations

Answer: V = 0.23 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.

Weight in kg

50.6/2.2 = 23 kg

Dose

0.5·23 = 11.5 mg

Volume

V = (11.5/250)·5 = 0.23 mL

Answer

V = 0.23 mL
5.IV infusion rates

Answer: R = 145 mL/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.

Original rate

1500/12 = 125 mL/h

New rate

R = 1450/10 = 145 mL/h

Answer

R = 145 mL/h

Many hospitals allow such an adjustment up to 25% without a new order; check local policy.

6.IV infusion rates

Answer: t = 6.7 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

30·60/20 = 90 mL/h

Time left

t = 600/90 = 6.667 ≈ 6.7 h

Answer

t = 6.7 h

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