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An Evaluation of Sexually Transmitted Infection and Odds of Preterm or Early-Term Birth Using Propensity Score Matching

Baer, Rebecca J., MPH*†; Chambers, Christina D., PhD*; Ryckman, Kelli K., PhD; Oltman, Scott P., MS†§; Rand, Larry, MD†¶; Jelliffe-Pawlowski, Laura L., PhD†§

Sexually Transmitted Diseases: June 2019 - Volume 46 - Issue 6 - p 389–394
doi: 10.1097/OLQ.0000000000000985
Original Studies

Background Few studies have examined the relationship between sexually transmitted infections (STIs) and preterm birth (<37 weeks gestation) by subtype (<32 weeks, 32–36 weeks, spontaneous, provider-initiated). Here, we evaluate the odds of preterm (by subtype) and early-term (37 and 38 weeks gestation) birth in women with an STI compared with a propensity score-matched reference population.

Methods The sample was selected from California births in 2007 to 2012. Sexually transmitted infection was defined as a maternal diagnosis of chlamydia, gonorrhea, or syphilis in the birth certificate or hospital discharge record. A reference sample of women without an STI was selected using exact propensity score matching on maternal factors. Odds of preterm and early-term birth were calculated.

Results Sixteen thousand three hundred twelve women were identified as having an STI during pregnancy and an exact propensity score-matched control was identified for 97.2% (n = 15,860). Women with an indication of syphilis during pregnancy were at 1.6 times higher odds of having a preterm birth and, in particular, at elevated odds of a birth less than 32 weeks due to preterm premature rupture of the membranes or provider-initiated birth (odds ratios 4.0–4.2). Women with gonorrhea were at increased odds of a preterm birth, a birth less than 32 weeks, or an early-term birth (odds ratios 1.2–1.8). Chlamydia did not raise the odds of either a preterm or early-term birth.

Conclusions Gonorrhea and syphilis increased the odds of a preterm birth. Gonorrhea also increased the odds of an early-term birth. Chlamydia did not raise the odds of an early birth.

Mothers in California with an indication of gonorrhea or syphilis on their birth record were at higher odds of birth at less than 32 weeks of gestation.

From the *Department of Pediatrics, University of California San Diego, La Jolla;

California Preterm Birth Initiative, University of California San Francisco, San Francisco, CA;

Departments of Epidemiology and Pediatrics, University of Iowa, Iowa City, IA;

§Department of Epidemiology and Biostatistics, and

Department of Obstetrics, Gynecology and Reproductive Sciences, University of California San Francisco, San Francisco, CA

Conflicts of Interest: None declared.

Funding: Supported by the California Preterm Birth Initiative within the University of California, San Francisco.

Correspondence: Rebecca J. Baer, MPH, Department of Pediatrics, University of California San Diego, 9500 Gilman Drive, MC0828, La Jolla, CA 92093. E-mail:

Received for publication September 27, 2018, and accepted January 14, 2019.

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© Copyright 2019 American Sexually Transmitted Diseases Association