Q&a attempts to provide balanced answers to those curly-yet-common questions in obstetrics and gynaecology for the broader O&G Magazine readership, including Diplomates, Trainees, medical students and other health professionals.
A patient, aged 28, G2P1 at 31/40 gestation, presents to a small regional hospital with what appear to be contractions every five minutes. She had a normal vaginal delivery with her first baby at 38 weeks with no complications. She is otherwise well and a non-smoker.
This presentation is not uncommon and can present a conundrum for clinicians working in rural regions. The difficulty comes in making the decision regarding whether or not this patient is in preterm labour and whether or not she is at risk of delivery in the near future. If the cervix is 2 to 3 cm dilated, the decision is easy: proceed with antibiotic prophylaxis, steroid loading and tocolysis, and transfer to a tertiary centre. However, when the cervix is long and closed, with regular uterine activity, when should a patient be transferred to a tertiary centre for continuing care?
Initial assessment should begin with a full history, with particular focus on onset of, and length of contractions, presence of vaginal loss, and fetal movements. At this point, running through the general antenatal and personal medical and surgical history is warranted.
Initial examination should include abdominal palpation to determine presentation, along with timing of contractions. Baseline CTG will assist in assessment of fetal well-being. A speculum examination should be performed to view the cervix, with collection of preterm swabs and assessment for preterm premature rupture of the membranes (PPROM) with an amnicator. Use of fetal fibronectin testing at this point has become a useful part of the initial assessment process – a negative result can certainly aid in formulating a management plan.
Fibronectins are large glycoproteins found in the plasma and extracellular matrix. Fetal fibronectin is a unique fibronectin that has been identified in amniotic fluid, extracts of placental tissue and malignant cell lines. It is thought to be a ‘trophoblast glue’, promoting cellular adhesion at utero-placental and decidual-fetal interfaces. When the extracellular matrix of the chorionic/decidual interface is disrupted, it is released into cervicovaginal secretions. Fetal fibronectin is normally present in the cervicovaginal secretions prior to 22 weeks, thus testing in the first half of the pregnancy is not useful.
The collection process involves sampling from the secretions in the posterior fornix or external cervical os during a speculum examination, using a swab from the manufacturer’s kit. Manipulation of the cervix (digital or ultrasound examination, coitus within 24 hours) and introduction of intravaginal lubricants or medications should be avoided pre-examination, as this can lead to a false positive or false negative result.
The value of testing for fetal fibronectin in symptomatic women has been demonstrated in a systematic review1 including 40 prospective studies evaluating cervical and vaginal fetal fibronectin for predicting preterm delivery. A positive test was obtained in almost 80 per cent of women who went on to deliver within the next seven days. Iams et al concluded that the assay was superior to the usual clinical assessments for predicting preterm delivery in symptomatic women, such as digital cervical assessment.2
The high negative predictive value of fetal fibronectin proves to be the most beneficial aspect of the test, particularly in women with preterm contractions in whom the diagnosis of preterm labour is uncertain. In a study by Peaceman et al, 99.5 per cent of pregnant women who presented initially with signs and symptoms of preterm labour and who had a negative cervicovaginal test, failed to deliver within seven days.3 In contrast, its high false positive rate makes
it less than optimal for prediction of preterm delivery, but should still prompt consideration of administration of glucocorticoids to accelerate fetal lung maturation.
Initial blood work should include a complete blood count, C-reactive protein, along with a group and save, and urine culture. If available, ultrasound assessment to confirm presentation, liquor volume and cervical length (if possible) can be very useful for assisting in the decision-making process, but is not always a readily accessible option. Women with a cervical length of greater than 30 mm have been shown to be unlikely to deliver preterm.4
When the decision is made that a woman is at an increased risk of delivery within the next seven days, transfer to the nearest tertiary centre should be organised at the same time as the commencement of antibiotic prophylaxis with Benzylpenicillin IVI. Controlled trials have shown a reduction in maternal infection with the use of antibiotics (prophylactically) for preterm labour with intact membranes, but have shown no benefit in neonatal outcomes.5 Of note, Oracle II concluded that some prophylactic antibiotics (amoxycillin + clavulanic acid) actually increase the rate of neonatal morbidity.6
In a gestation of less than 34 weeks, give betamethasone 11.4mg IM, then repeat in 24 hours. Corticosteroids are effective in preventing adverse perinatal outcomes, most notably respiratory distress syndrome, and in increasing the likelihood of neonatal survival.7
Consider tocolysis (even if 34 to 37 weeks gestation) using nifedipine 20 mg STAT (chewed), followed 30 minutes later by a repeat dose and three-hourly from thereon. There may be an indication for salbutamol infusion use for transfer of a woman in threatened preterm labour (TPL), however, there are numerous contraindications to consider, along with a side-effect profile that may prohibit its use. With respect to neonatal outcome, Tstatsaris et al showed that nifedipine appears to be more effective than beta-agonists for tocolysis and should be considered for use as a first-line tocolytic agent.8
If, however, delivery is imminent, the patient may need to be delivered at the rural centre, with a neonatal retrieval team organised early to retrieve the baby. This is a decision which can be made in conjunction with the obstetric and paediatric teams from the referral base. A delivery in a hospital with readily available neonatal resuscitation equipment is preferable to delivery in transit.