Preterm labor refers to childbirth in which regular uterine contractions lead to cervical dilation after the 20th week and before the 37th week of pregnancy and, if untreated, may result in the birth of a premature infant. Maternal complications of preterm labor include severe bleeding, uterine infection, admission to the intensive care unit (ICU), psychological disorders such as anxiety and postpartum depression, or even death. These complications are more common among women between 23 and 27 weeks of gestation. Spontaneous preterm labor primarily occurs due to ascending infection in the vagina and cervix. These infections, by predisposing physiological conditions in the body, may lead to cervical shortening. As a result of the body’s immune response, defensive reactions against bacteria causing bacterial vaginosis and cervicitis are initiated, and phagocytosis is carried out by neutrophils and macrophages. Eventually, due to the release of proteolytic enzymes, cervical inflammation occurs. However, cases of cervical shortening without obvious infection or vaginal/cervical inflammation have also been observed. In general, infections caused by microbial agents, including bacterial vaginosis, should be managed and treated before pregnancy, especially in patients with a history of preterm birth. If the causative agent of bacterial vaginitis is identified during pregnancy, approved antibiotic medications may be used; however, their effectiveness should be considered alongside other available methods. In cases of abscesses and obstructed cavities such as the vagina, other methods such as puncture, drainage, or irrigation may also be effective. Just as gargling is effective in relieving symptoms of upper respiratory tract infections, vaginal irrigation may also be beneficial in cases of vaginal or cervical infection. However, probably because vaginal douching (VD) is not a common practice among most women, related studies are limited. The present study aimed to determine the effectiveness of vaginal douching using saline solution in patients with short cervical length and subclinical infections in this region, based on the results of randomized controlled trials (RCTs) conducted in Japan. In this investigation, a group of mothers meeting the above conditions was selected and examined. The study population consisted of pregnant women between 16 and 26 weeks of gestation with a cervical length ≤ 25 mm, who were randomly assigned to two treatment groups: • BR: Bed rest (without vaginal douching) • VD: Bed rest (with vaginal douching) Patients in the BR group had no asymptomatic vaginal infection, whereas patients in the VD group had asymptomatic vaginal infection. The BR group was prescribed 2 weeks of bed rest, while the VD group received bed rest until 32 weeks of gestation along with vaginal douching using 500 mL saline solution. Other therapeutic interventions were standardized. The primary and secondary endpoints were preterm delivery (gestational weeks at delivery) and transfer of premature infants to the neonatal intensive care unit (NICU), which was defined as the level of tocolytic drug use. The purpose of administering these drugs is to stop labor and provide more time for fetal growth. The following medications are used in the treatment of preterm labor: Tocolytics: These medications stop contractions for up to 48 hours to delay premature delivery. After delaying labor, magnesium sulfate or corticosteroids may be prescribed by the attending physician. Corticosteroids help the development of the fetal lungs, digestive organs, and brain before birth. These drugs are usually prescribed between 24 and 34 weeks of pregnancy. In this study, the research group analyzed 30 and 35 cases in the BR and VD groups, respectively (including those transferred to the resuscitation unit). Patient background characteristics and delivery outcomes, including mean delivery time, gestational age at delivery, birth weight, and neonatal birth status, showed no significant differences. The VD group had a longer gestational period compared with the BR group (up to 32 weeks of gestation). The VD group showed a significantly greater effect in prolonging pregnancy duration by 70 days compared with the BR group. In addition, the VD group (10 cases, 28.6%) showed a lower but non-significant tendency for transfer to the NICU compared with the BR group (12 cases, 40.0%). In other words, in patients with short cervix, cervicitis, or vaginitis, vaginal douching with saline solution may prolong pregnancy duration and reduce preterm birth, thereby improving maternal and neonatal outcomes.

Vaginal Douching is often performed to eliminate unpleasant odor and perfume the vagina, which differs from the method used in most medical centers. Although injection of solution into the vagina is not routinely performed, cleansing the vagina with warm water while using the toilet is a common practice in Japan. According to a study conducted by Asakura et al., this method not only does not contribute to the occurrence of vaginosis, but also effectively prevents urinary tract infections and improves vaginal symptoms in premenopausal women. The results of this study, based on data obtained from a randomized clinical trial conducted on pregnant mothers between January 2005 and November 2011, provide valuable evidence regarding the usefulness of VD in preventing preterm birth in patients with cervicitis and bacterial vaginitis. Thus, VD using 500 mL normal saline in patients with short cervix, cervicitis, or bacterial vaginitis significantly reduces the rate of preterm delivery at gestational ages of less than 34 weeks and less than 30 weeks, respectively.