Premature Labour
Premature (preterm) labor is defined as the presence of uterine contractions of sufficient frequency and intensity to effect progressive effacement and dilation of the cervix prior to term gestation (between 20 and 37 weeks).
Preterm labour and birth accounts for 70% of neonatal morbidity, mortality and early identification of at-risk gravidas with timely referral for subspecialised obstetrical care may help identify women at risk for preterm labor and delivery and decrease the extreme prematurity (
Diagnosis
Preterm labor may be difficult to diagnose and the potential exists for overtreatment of uterine irritability.
Four or more contractions in 1 hour.
Cervical dilatation and effacement
PV bleeding
Vaginal pressure
Abdominal or back pain
The diagnosis of suspected threatened preterm labour on clinical grounds should include uterine contractions that are painful, palpable, last more than 30 seconds and occur with a frequency of at least 2 every 10 minutes.
Fetal fibronectin
The presence of this glycoprotein in the cervical or vaginal secretions indicates that the border between the chorion and deciduas has been disrupted. A positive test indicates an increased risk of preterm birth, and a negative test has a high predictive value. Beware of false positive fibronectin tests after digital examinations of the cervix, so do it first. If labour becomes apparent then simply don't run the test.
Ultrasonography of the cervix
Obstetric US has become useful in the assessment of the cervix in women at risk for premature delivery. A short cervix preterm is undesirable. At 24 weeks gestation a cervix length of less than 25mm defines a risk group for preterm birth. And the shorter the cervix the greater the risk. Conversely cervix lengths exceeding 30mm are unlikely to deliver within the next week.
Aetiology
50% are never determined. Can include most things other than normal, in terms of age size, pregnancy interval and many others.
Four general pathways exist:
precocious fetal endocrine activation, maternal endocrine disorders, presence of antithyoid antibodies
uterine overdistension, multigravidas
decidual bleeding, abruption
intrauterine inflammation/infection, vaginosis, UTI, ( 25-40% ) others include, asymptomatic bacteriuria, pneumonia, and appendicitis. Also periodontal disease.
Fetal well being
In terms of fetal well being one of the most significant risks is that of respiratory distress syndrome, also called hyaline membrane disease, in the neonate.
Steroids
Typical glucocorticoids that would be administered in this context are betamethasone (11.4 mg IM) or dexamethasone, often when the fetus has reached viability at 23 weeks. In cases where premature birth is imminent, a second "rescue" course of steroids may be administered 12 to 24 hours before the anticipated birth. There is no research consensus on the efficacy and side-effects of a second course of steroids, but the consequences of RDS are so severe that a second course is often viewed as worth the risk. Beside reducing respiratory distress, other neonatal complications are reduced by the use of glucocorticosteroids, namely intraventricular haemorrhage, necrotising enterocolitis, and patent ductus arteriosus.
Antibiotics
The routine administration of antibiotics to all women with threatened preterm labor reduces the risk of group B streptococcus infection and related mortality rates.
The use of Magnesium Sulphate to cut the rate of cerebral palsy is not yet known but work is currently being done looking at this.
Tocolytics
Agents for threatened preterm labour before 34 weeks gestation:
Give an initial dose of 20mg oral Nifedipine stat, followed by 20mg nifedipine orally given at 30 minute intervals for a total of three doses if required and if the BP is stable.
10mg nifedipine immediate release tablet (medium acting) is the preferred presentation to treat TPL.
For a detailed state-wide current policy on tocolytic agents for threatened preterm labour before 36 weeks gestation (GL2022_006) from NSW Health click here.
Management
Make the diagnosis
Seek help
ABCDEs
Estimate gestational age
Perform and expedite results of tests
Prepare for resuscitation
Antibiotics
Steroids
Tocolytics
Transfer indicated?