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. 2023 Jun 5;11(11):1657.
doi: 10.3390/healthcare11111657.

The Effect of Sexual Intercourse during Pregnancy on Preterm Birth: Prospective Single-Center Cohort Study in Japan

Yoshie Yo  1 , Kaoru Kawasaki  1 , Kaori Moriuchi  1 , Reona Shiro  1 , Masao Shimaoka  2 , Noriomi Matsumura  1
Affiliations

The Effect of Sexual Intercourse during Pregnancy on Preterm Birth: Prospective Single-Center Cohort Study in Japan

Yoshie Yo et al. Healthcare (Basel). .

Abstract

Several studies in Europe and the United States have shown that sexual intercourse (SI) during pregnancy is not associated with preterm birth. However, it is unclear whether these findings apply to pregnant Japanese women. The aim of this prospective cohort study was to elucidate the influence of SI during pregnancy on preterm birth in Japan. A total of 182 women who underwent antenatal care and delivery were included in this study. The frequency of SI was assessed using a questionnaire, and its association with preterm birth was analyzed. The results showed that SI during pregnancy was associated with a significantly higher cumulative preterm birth rate (p = 0.018), which was more pronounced for SI more than once a week (p < 0.0001). Multivariate analysis showed that SI, bacterial vaginosis in the second trimester, previous preterm birth, and smoking during pregnancy were independent risk factors for preterm birth. The combination of SI and second trimester bacterial vaginosis was associated with a 60% preterm birth rate, whereas either factor alone was associated with a lower rate, suggesting a synergistic effect (p < 0.0001). Future studies are needed to investigate the effect of prohibiting SI in pregnant women with bacterial vaginosis on preterm birth.

Keywords: bacterial vaginosis; preterm delivery; sexual intercourse during pregnancy.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
The association between sexual intercourse (SI) during pregnancy and the cumulative preterm birth rate. (A) Comparison based on whether or not there was SI, regardless of frequency. (B) Comparison among three groups divided by frequency of SI. The vertical and horizontal axes show the cumulative preterm birth rate (%) and the gestational age at preterm birth (weeks), respectively. wk—weeks; mo—months.
Figure 2
Figure 2
The association between the known risk factors for preterm birth and the cumulative preterm birth rate. (A) Comparison based on presence or absence of bacterial vaginosis (BV) in the first trimester. (B) Comparison based on presence or absence of BV in the second trimester. (C) Comparison based on presence or absence of a past history of preterm birth. (D) Comparison between smokers and non-smokers during pregnancy. (E) Comparison of four groups divided by maternal age. (F) Comparison between multipara and primipara.
Figure 3
Figure 3
Combination of SI with BV in the second trimester and its association with the cumulative preterm birth rate.
See this image and copyright information in PMC

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