On this page
Study tools
Write your answer
Saved on this device. No marking — you are the marker.
Stem
A 27-year-old woman (G2P1) at 29 weeks gestation presents to the labour ward with regular painful uterine contractions every 4 minutes lasting 40 seconds. She had a spontaneous preterm birth at 30 weeks in her previous pregnancy. She is afebrile, pulse 92, BP 110/70. Sterile speculum shows no liquor pooling and no bleeding. A fetal fibronectin swab is taken. Transvaginal ultrasound shows a cervical length of 12 mm. CTG shows a fetal heart rate of 145 bpm with normal variability and no decelerations. Digital vaginal examination shows the cervix is 3 cm dilated and 60 percent effaced.
Questions
a) What is the diagnosis and what two findings establish it? (2 marks)
Established preterm labour (PTL). The two defining findings are: (1) regular painful uterine contractions before 37 weeks, and (2) cervical change (3 cm dilatation and 60 percent effacement). The very short cervix (12 mm) and prior preterm birth further confirm high risk. (Contractions without cervical change would be "threatened" PTL.)
b) Before initiating tocolysis, name FOUR conditions that would contraindicate tocolysis and mandate delivery instead. (2 marks)
- Chorioamnionitis (maternal fever, fetal tachycardia, uterine tenderness, foul liquor).
- Non-reassuring fetal status / fetal compromise on CTG.
- Suspected placental abruption (painful bleeding, woody tender uterus).
- Gestational age 34 weeks or more (or severe pre-eclampsia/eclampsia, lethal anomaly, or intrauterine fetal death).
c) Outline the management bundle for this woman over the next 48 hours. (4 marks)
- IV access, FBC, group and save, CRP, MSU, swabs; left lateral position; analgesia.
- Tocolysis with NIFEDIPINE 20 mg PO then 10 to 20 mg every 6 to 8 hours (calcium-channel blocker, first-line, oral) — to delay birth for approximately 48 hours. Avoid combining with magnesium.
- Antenatal corticosteroids — BETAMETHASONE 12 mg IM, two doses 24 hours apart (or DEXAMETHASONE 6 mg IM, four doses 12 hours apart), as she is between 24 and 34 weeks. Reduces RDS, IVH, NEC and neonatal death.
- Magnesium sulfate for neuroprotection — 4 g IV loading over 30 minutes then 1 g per hour — as she is under 32 weeks (reduces cerebral palsy). Have calcium gluconate at the bedside; monitor reflexes, respiratory rate, oxygen saturation, urine output.
- GBS prophylaxis if indicated (IV benzylpenicillin 3 g then 1.5 g every 4 hours).
- Arrange in-utero transfer to a unit with NICU capability if the local unit cannot care for a 29-week infant.
- Neonatal team informed and to attend delivery.
d) What is the role of fetal fibronectin in this presentation, and how should the result be interpreted? (1 mark)
Fetal fibronectin (fFN) is principally a rule-OUT test. A negative result (under 50 ng/mL) carries a risk of delivery within 7 to 14 days of under 1 percent; a positive result has a positive predictive value of only about 40 percent (weak rule-in). The swab must be taken before any digital VE (which causes false positives). In this woman, the established cervical change already makes the diagnosis, so fFN is not needed to guide the acute decision but would be reassuring if negative.
e) Name FOUR risk factors in this woman's history for recurrent preterm birth, and outline prevention for her NEXT pregnancy. (1 mark)
Risk factors: previous spontaneous preterm birth (strongest; recurrence 20 to 30 percent), short cervix (12 mm), possibly infection (to screen for), and any cervical/uterine factor.
Prevention in the next pregnancy: serial transvaginal cervical length from 16 to 24 weeks; vaginal progesterone (200 mg nocte) for short cervix; history-indicated cervical cerclage at 12 to 14 weeks if criteria met; smoking cessation, treat infection, ensure adequate interpregnancy interval, optimise nutrition and BMI. Note: 17-OHPC (Makena) is no longer recommended (PROLONG failed; FDA withdrew approval 2023).