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

When the newborn's head is turned to one side, the arm on that side extends and the other arm flexes. Which reflex is this?

  1. APalmar grasp reflex
  2. BRooting reflex
  3. CTonic neck reflex
  4. DMoro reflex
2.Maternity & obstetric nursingHard

A newborn is jaundiced at 12 hours of age. The mother is blood group O, Rh-positive and the baby is group A, Rh-positive with a positive direct Coombs test. What is the most likely cause?

  1. AABO incompatibility
  2. BRh isoimmunisation
  3. CPhysiological jaundice
  4. DBreast milk jaundice
3.Dosage calculationsMedium
1:1000ampouleV = ? mL

An ampoule of epinephrine (adrenaline) is labelled 1:1000 (1 mg/mL). The prescription is 0.15 mg IM for anaphylaxis. What volume V do you draw up?

1:10000.15 mg
V = mL
4.Dosage calculationsHard
10%stockV₁ = ? mL

You must prepare 200 mL of a 2.5% (w/v) solution from a 10% (w/v) stock solution. What volume of stock V₁ do you need?

C₁ = 10%C₂ = 2.5%V₂ = 200 mL
V₁ = mL
5.IV infusion ratesMedium
1500 mL10 gtt/mL8 h? gtt/min

Infuse 1500 mL over 8 hours with a giving set of 10 gtt/mL. Find the drip rate R in drops per minute. Round to the nearest whole number.

1500 mL8 h10 gtt/mL
R = gtt/min
6.IV infusion ratesHard
190 mLleft? mL/h2 h left

500 mL was ordered over 6 hours. After 4 hours you find that 190 mL is still in the bag, and the order must still finish on time. By what percentage Δ must the original pump rate be increased?

500 mL / 6 hafter 4 h: 190 mL
Δ = %

3Solutions

1.Maternity & obstetric nursing

Answer: C · Tonic neck reflex

Why this is the answer

The asymmetric tonic neck reflex gives a "fencing" posture. It fades over the first months; persistence beyond the expected age can suggest neurological problems.

Answer

C · Tonic neck reflex
2.Maternity & obstetric nursing

Answer: A · ABO incompatibility

Why this is the answer

Group O mothers have anti-A and anti-B antibodies that can cross the placenta and haemolyse the red cells of a group A or B baby. Early jaundice with a positive direct Coombs test suggests haemolysis. Both are Rh-positive, so Rh disease is excluded.

Answer

A · ABO incompatibility
3.Dosage calculations

Answer: V = 0.15 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.

Concentration

1:1000 = 1 g/1000 mL = 1 mg/mL

Volume

V = 0.15/1 = 0.15 mL

Answer

V = 0.15 mL

US labels now state mg/mL (1 mg/mL = 1:1000; 0.1 mg/mL = 1:10 000). Never give 1 mg/mL epinephrine IV push.

4.Dosage calculations

Answer: V₁ = 50 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 = 2.5·200/10 = 50 mL

Answer

V₁ = 50 mL
5.IV infusion rates

Answer: R = 31 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

8·60 = 480 min

Drip rate

R = 1500·10/480 = 31.25 ≈ 31 gtt/min

Answer

R = 31 gtt/min

At the bedside you round to the nearest whole drop: 31 gtt/min.

6.IV infusion rates

Answer: Δ = 14 %

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

500/6 = 83.33 mL/h

New rate

R = 190/2 = 95 mL/h

Percentage change

Δ = (95 − 83.33)/83.33·100% = 14%

Answer

Δ = 14%

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

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