Medical practice

Using condoms linked to better vaginal health

"Could condoms boost vaginal health?" the Mail Online asks.

The question is prompted by a Chinese study that looked at whether using condoms was linked to the presence of "good" bacteria in the vagina.

A healthy vagina normally contains a balance of "good" and "bad" bacteria. But sometimes an imbalance between the two can result in a common infection called bacterial vaginosis (BV). The most common symptom of BV is a fishy smelling discharge from the vagina.

The study found that women who used condoms had higher levels of a strain of bacteria called lactobacillus, which is thought to protect against infection, than women who used intrauterine devices (IUDs – commonly known as the 'coil'). The authors conclude that condom use may protect against bacterial vaginosis.

However, this cross-sectional study cannot prove that condoms promote the presence of "good" bacteria in the vagina. There are many other factors that may affect the balance of bacteria in the vagina, including a woman’s sexual history and whether she smokes or uses vaginal deodorants. 

Condom use is recommended as it lowers the risk of sexually transmitted infections, including HIV, as well as unintended pregnancy.

Where did the story come from?

The study was carried out by researchers from Capital Medical University, China. There is no information about external funding.

The study was published in the peer-reviewed open access journal PLOS One.

The study was reported uncritically by the Mail Online, which also reported the assertion made by the researchers that the presence of "good" bacteria in the vagina may be linked to a lower risk of HIV infection. The link between bacteria in the vagina and the risk of HIV infection is not yet proven.

What kind of research was this?

This was a cross-sectional study looking at the association between non-hormonal methods of contraception, the presence of lactobacilli in the vagina and the potential effect of any association on women’s reproductive health. Cross-sectional studies look at all data at the same time. Although they are useful for showing up patterns or links in the data, they cannot be used to confirm that one thing is the result of another.

The authors say that in China non-hormonal methods of contraception such as condoms, IUDs and the rhythm method are the most commonly used. Because of the one child policy adopted by the Chinese regime the regular use of contraception is thought to be higher than in most Western states.

In a healthy vagina, they say, lactobacillus bacteria are thought to play an important role in preventing BV and HIV by producing lactic acid and hydrogen peroxide (H202), which both guard against pathogens (germs).

Lactobacilli make the vagina slightly acidic, which usually prevents other bacteria from growing there. Low levels of lactobacilli in the vagina can allow other types of bacteria to grow and result in BV, a common infection. The authors say that BV may lead to pelvic inflammatory disease, increased risk of STIs and preterm delivery in pregnant women.

Previous research has suggested that condom use is associated with a reduction in the risk of BV, though little is known about the effect of non-hormonal contraceptives on the presence of vaginal lactobacilli, the researchers say.

What did the research involve?

In 2010, researchers recruited 165 healthy, sexually active women between 18 and 45 years of age who had been consistently using the same method of contraception for more than three months.

Women were eligible if they:

  • had been sexually active with a male partner in the past three months
  • had no active itching or burning sensation around the vulva
  • had normal levels of acidity in the vagina
  • had no indication of bacterial vaginosis

Exclusion criteria included pregnancy or breastfeeding, chronic illness, use of antibiotics and other drugs that can affect levels of good bacteria, use of hormonal methods of contraception, history of urinary tract or gynaecological infections or a current vaginal infection.

The women were divided into different groups according to which contraceptive method they used. On day 21 or 22 of each woman’s menstrual cycle, vaginal swabs were collected and tested for:

  • the Nugent score – a system used to diagnose the presence of BV based on the number of bacteria found during a smear test
  • presence of vaginal lactobacilli by quantity (colony count)
  • polymerase chain reaction – a DNA technology that identifies the genetic strain and influence of the lactobacilli bacteria 

The prevalence of lactobacilli, their colony counts and their gene expression was then compared between the different groups. Gene expression is the process through which the information in our genes is used to produce proteins. Measuring the level of gene expression shows how active a gene is.

What were the basic results?

Researchers found that 72 of the women always used condoms, 57 had IUDs and 35 used the rhythm method.

  • a Nugent score of 0–3 (the normal state) was more common in the condom group (93.1%) than in the group that used an IUD (75.4%)
  • the prevalence of lactobacilli was significantly higher in the condom group (82.3%) than in the IUD group (68.2%)
  • there was a significant difference in colony count of lactobacilli between condom users (7.8160.14) and IUD users (6.5460.14)
  • the gene expression of a strain called Lactobacillus crispatus was significantly higher in the condom group (8.0960.16) than in the IUD group (6.0360.18)

How did the researchers interpret the results?

The researchers say that condom use can play a positive role in protecting women’s reproductive health by promoting the colonisation of lactobacillus in the vagina. They say that this may help protect against both BV and HIV.

Condoms, they say, can help maintain the vaginal acidic "buffer system" and the vaginal lactobacilli population when sperm enter the vagina during sex.

L. crispatus, they say, is one of the hydrogen peroxide producing lactobacilli and plays an important role in the prevention of infections including BV and HIV.


This cross-sectional study is of interest but it cannot show that condom use boosts the number of "friendly" vaginal bacteria or protects against BV. There are many factors that may affect the balance of bacteria in the vagina, including how many sexual partners a woman has, and lifestyle factors, such as whether she smokes or uses vaginal deodorants.

These researchers do not describe the type of condom used and which, if any, spermicides were used. As these can also affect the vaginal microflora it’s important that any future studies ask about and control for these.

Using condoms correctly is known to protect against sexually transmitted infections, including HIV, and lowers the risk of unplanned pregnancy. Whether condoms can also help keep a healthy balance of bacteria in the vagina or protect against BV is unclear and not proven by this study.

NHS Attribution