CLINICAL CASE
Unit Two: Obstetrics
Section B: Abnormal Obstetrics
Objective 24: Preterm Labor
A 20-year-old African-American, who is 28 weeks pregnant, presents to the labor unit
complaining of contractions. The contractions began 8 hours ago and have increased
in frequency and duration. She notes that, for the last two days, she has had increased
vaginal discharge and some lower back pain. Her prior pregnancy was complicated by
preterm labor and premature ruptured membranes at 26 weeks gestation. The
neonates course was complicated by intra-ventricular hemorrhage and necrotizing
enterocolitis.
PMH
Medical
Surgical
Obstetric
neg
appendectomy age 11
gravida 3 para 2 one preterm delivery, living children 2, one
with cerebral palsy
Physical examination
Vital Signs
kg
General
Cardiac
Abdomen
Vaginal exam
Temp 36.5oC (97.8oF), pulse 64, respiration 20, BP 100/60, wt 49
Thin women of stated gestational age
Regular rate and rhythm, no rubs, gallops or clicks
No hepatosplenomegaly, fundal height 27 cm
No fluid per os; cervix – 3cm dilated and completely effaced;
vertex presentation
AP
Preterm labor at 27 weeks gestation plan for tocolysis, steroids and penicillin for
Group B streptococcus prophylaxis
Discussion
Preterm birth is one of the major health hazards of our time. It is the leading cause of
neonatal morbidity and mortality. Approximately 11-12% of births occur prior to 37
wk. gestation. Roughly 1/3 is due to preterm labor, 1/3 to preterm premature
ruptured fetal membranes and 1/3 to medical or fetal complications. Efforts to reduce
or prevent preterm birth are largely unsuccessful.
Preterm birth is defined as that occurring less than 37 wk. in the presence of regular
uterine contractions (4 per 20 min or 8 per 60 minutes) with cervical change or if the
cervix is 2 cm dilated and 80% effaced. There are many possible causes of preterm
labor, including infection, faulty placentation, uterine factors (leiomyomata, uterine
didelphys), overdistension of the uterus (multifetal gestation, polyhydramnios),
immunologic causes, drug use (such as cocaine), and idiopathic. Risk factors for
preterm birth can be subdivided into pre-pregnancy (i.e. low maternal weight and
prior preterm birth) and pregnancy-related (twins, abnormal placentation, maternal
factors).
Management of women with preterm labor involves tocolytics to reduce or stop the
contractions (evidence is weak that tocolytics works longer than 24-48 hours),
corticosteroids to enhance lung maturation and decrease the likelihood of neonatal
respiratory distress syndrome and penicillin intrapartum to prevent early onset
neonatal GBS infection.
Tocolytics can be divided into major categories with various degrees of efficacy,
safety, side effect profiles, costs, etc. Categories include B-sympathomimetic (ritodrine
and terbutaline), magnesium sulfate, prostaglandin synthetase inhibitors
(indomethacin), calcium channel blockers (nifedipine) and oxytocin inhibitors
(atosiban).
Teaching points
-
Preterm birth is a common pregnancy complication
Risk factors for preterm labor/birth are many; however the most
common risk factors are prior preterm birth and low maternal weight
Diagnosis of preterm labor is difficult
Management includes hydration, tocolytics (a high rate of failure to
prevent preterm birth), corticosteroids and antibiotics