Methods
This was a retrospective study of pregnant individuals who had
Ureaplasma cervical culture at an academic institution from January 2014
to December 2020. Our Institutional Review Board approved this study. In
2014, we started a quality improvement project in which we routinely
obtained Ureaplasma cervical culture for all pregnant individuals with
risk factors for preterm birth (history of preterm births or PPROM,
history of recurrent pregnancy loss, pregnancy with multiple gestations,
or pregnancy requiring cerclage). The American College of Obstetricians
and Gynecologists (ACOG) defined preterm birth as delivery less than 37
weeks’ gestation. PPROM was defined as rupture of membranes prior to the
onset of labor less than 37 weeks’ gestation. Recurrent pregnancy loss
is defined as 2 or more consecutive early pregnancy losses. Indications
for cerclage included history indication, ultrasound indication due to
the short cervix, or physical exam indication. These indications were
documented in the medical record.
We excluded individuals who had Ureaplasma cervical culture for preterm
contraction, multiple gestation, or unknown indications. Therefore, we
only analyzed pregnant individuals with singleton pregnancies who had
Ureaplasma cervical culture that was obtained for a history of preterm
births, a history of recurrent pregnancy loss, or cervical cerclage. We
also limited analyses to pregnant individuals who had Ureaplasma
cervical culture at or prior to 20 weeks’ gestation, since we wanted to
assess the effectiveness of early intervention. In addition, we excluded
pregnant individuals if they delivered within two weeks of the initial
Ureaplasma cervical culture since these individuals would not have
enough time to receive the treatment. Pregnant individuals were
categorized according to the initial Ureaplasma cervical culture results
and whether they received appropriate antibiotics (negative; positive
and received treatment; and positive but did not receive treatment
[including those who did not receive appropriate antibiotics]).
Ureaplasma cervical culture was obtained at the first prenatal visit by
inserting a vaginal speculum and removing the excess mucus from the
cervical opening, using a cotton swab. The specimen collection swab was
then placed within the external cervical os and gently rotated for 30
seconds for appropriate sampling. The swab was then removed avoiding
contact with the vaginal walls and immediately placed into the transport
tube which was securely capped. Aptima® swab was commonly utilized for
this procedure. This test detects Mycoplasma genitalium, Mycoplasma
hominis, and Ureaplasma species through nucleic acid amplification. If
Ureaplasma cervical culture was positive, we prescribed Azithromycin for
pregnant individuals and Doxycycline for sexual partners (Box 1). If
pregnant individuals received antibiotics, we obtained Ureaplasma
cervical culture 4 weeks after the initial treatment and treated them
again if the second cervical culture was positive. Alternative
antibiotics regimens in case of drug allergy are presented in Box 1.
Our primary outcome was gestational age at delivery. The estimated due
date (EDD) was based on the date of the last menstrual period confirmed
by first-trimester ultrasound. Secondary outcomes included Ureaplasma
cervical culture positive 4 weeks after the initial treatment (treatment
failure), preterm birth less than 37 weeks’ gestation, spontaneous
preterm birth less than 37 weeks’ gestation, spontaneous preterm birth
less than 34 weeks’ gestation, chorioamnionitis, PPROM, pregnancy loss
less than 22 weeks’ gestation, neonatal intensive care unit (NICU)
admission, neonatal respiratory distress syndrome (RDS) or transient
tachypnea of newborn (TTN), and stillbirth or neonatal demise.
Ureaplasma treatment failure rates were assessed according to the
indications for Ureaplasma cervical cultures. For the analysis of the
treatment failure rate, we only included pregnant individuals who had a
positive Ureaplasma cervical culture, received treatment, and had a
repeat Ureaplasma cervical culture after the initial treatment. Because
some individuals had several indications for Ureaplasma cervical
cultures, we classified mutually exclusive categories for indications
using the following hierarchy. First, if individuals had cerclage, the
indication was classified as “cerclage.” Second, if individuals had a
history of preterm births, the indication was classified as “history of
preterm birth.” Third, if individuals had a history of recurrent
pregnancy loss, the indication was classified as “recurrent pregnancy
loss.” The hierarchy was maintained if individuals had more than one
indication, with the highest-order indication prioritized to assign the
classification. For example, if an individual had a history of preterm
birth and underwent cervical cerclage, this individual was classified as
“cerclage” group.
We calculated the sample size based on the following assumptions. We
assumed that 90% of individuals with a positive Ureaplasma culture
would receive treatment. To obtain an alpha of 0.05 and the power of
80% and detect a Hazard ratio of 0.6, we would need 224 individuals
with a positive Ureaplasma culture (201 with appropriate antibiotics and
23 without appropriate antibiotics).
Descriptive statistics were calculated for all study variables.
Chi-square test, Fisher’s exact test, Student’s t-test, Wilcoxon rank
sum test, or Kruskal-Wallis tests were performed as appropriate. A
P-value <0.05 was considered significant. We plotted the
Kaplan-Meier curves to investigate the association between the
gestational age at delivery and Ureaplasma culture results (negative;
positive and received treatment; or positive but did not receive
treatment). Log-rank test was performed to obtain P-value to compare
Kaplan-Meier curves. A Cox proportional regression model was used to
calculate Hazard ratio (HR) with 95% confidence intervals (95%CI),
controlling for variables with a P<0.05 based on bivariable
analyses. For secondary outcomes, multivariable logistic models were
used to calculate adjusted P-value and adjusted odds ratios (aOR) with
95% confidence intervals (95%CI), controlling for variables with a
P<0.05 based on bivariable analyses (Ureaplasma negative as a
referent). A simple logistic regression was used to examine the
association between the treatment failure rate and cervical culture
indications (history of preterm birth as a referent). All statistical
analyses were performed using Stata/SE 17.0 (StataCorp, College Station,
TX).