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Preterm Labor and Preterm Premature Rupture of Membranes
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4. Diagnosis
Case 4
A. L., a 29 y/o G6P1313 at 23 weeks by her dates presents for her first prenatal visit. She has an obstetric history of having delivered her first child at 37 weeks, followed by 3 preterm deliveries at 32, 28, and 26 weeks, following spontaneous preterm labor. She also had one early trimester miscarriage. The infant that delivered at 26 weeks succumbed to complications of prematurity after a protracted nursery course.
Diagnosis
The diagnosis of true preterm labor is not always easy. The textbook definition of 4 contractions in 20 minutes accompanied by cervical change is somewhat subjective. Due to normal biologic variation, some multiparous women walk about significantly dilated throughout the third trimester, but deliver at term. Likewise some nulliparous women may efface significantly earlier than usual. Serial cervical examinations may help you decide on cervical change, but is hampered by both inter- and intra-observer variability. Bloody show is almost always a reliable sign of true labor, but is not necessarily always seen. Preterm premature rupture of membranes (PPROM) should always be sought, as it may be occult or unnoticed or misinterpreted by the patient.
A common error when evaluating patients in suspected preterm labor is to perform a cervical digital exam as your first maneuver. (“Check her quick! We have to get her out of here!”) There are disadvantages to this approach. If the patient does not appear to be making obvious expulsive efforts, but is uncomfortable, she probably is remote from delivery, and you have some time…., so hold off on that cervical check! Observing her on the monitor for 30 minutes while you do other things will allow you to evaluate her contraction pattern and whether the fetus looks stable. A clean catch urinalysis occasionally detects an occult urinary tract infection as the etiology of the uterine activity. If her dating is not certain it is helpful to get an ultrasound for biometry and an estimated fetal weight. A low amniotic fluid index (AFI) may be your first clue to occult PPROM.
