Management of acute preterm labour
Confirmation of diagnosis
PTL can present very subtly, particularly in women with cervical insufficiency as painless dilatation can occur without the strong contractions normally associated with labour.
In very early gestations, the fetus may pass through only a partially dilated cervix. Therefore PTL must be ruled out in any pregnant woman presenting with abdominal or pelvic symptoms such as pain, increased pelvic pressure, vaginal bleeding, or abnormal vaginal discharge before 37 weeks.Timely identification of high-risk cases will allow for administration of steroids, tocolytics, and transfer to an appropriate neonatal unit. However, between 70% and 80% of women with symptoms of threatened PTL will continue their pregnancy and deliver at term. As 90% of symptomatic women with threatened PTL will not deliver within 7 days, an accurate diagnosis of PTL should be made before commencing interventions.
When managing a case of threatened PTL, the history of the presenting symptoms should be taken, the gestational age of the pregnancy recorded, and risk factors for PTB evaluated (Box 30.1). Other obstetric and non-obstetric causes should also be considered and investigated accordingly.
A physical examination should include vital signs and temperature, an assessment of general well-being, observation of any superficial trauma (particularly to the abdomen), uterine palpation making an assessment of size, tone, tenderness, and the presence of a fetal heart rate should be confirmed.
A speculum examination can be performed to evaluate cervical change, diagnose preterm rupture of the membranes, make an assessment of any bleeding, and take vaginal swabs if there are concerns regarding infection. Unless the cervix is open and the presenting part or bulging membranes can be clearly seen, it is very difficult to make a diagnosis of PTL without further assessment. A sample of urine should be dipstick tested for leucocytes and nitrites, and if positive cultured for antibiotic sensitivities. A positive urine dipstick should not prevent a full assessment for PTL.
If the membranes are intact, the gold standard assessment for prediction of the likelihood of sPTB is measurement of CL with TVUS. TVUS CL greater than 30 mm has a negative predictive value of PTL of 80-100% for PTB at less than 37weeks and greater than 95% for delivery within 7 days (38). However CL scanning is operator dependent and swab biomarker tests such as FFN, phIGFBP-1 and PAMG-1 are frequently used in the assessment setting for their high negative predictive value.
Symptomatic women with a short CL of less than 15 mm have a risk of 50-57% of delivering within 7 days (41, 75). However, the specificity of TVUS remains poor for women with a CL less than 30 mm and the performance of the test can be improved by the additional use of FFN (41).