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Bacteria influence the chance of pregnancy during IVF treatment

New Danish research shows that the chance of pregnancy through in vitro fertilisation (IVF) is affected by the composition of bacteria in the vagina.

2016.03.15 | Lotte Fisker Jørgensen

[Translate to English:] Ph.d.-studerende Thor Haarh, Institut for Klinisk Medicin, Aarhus Univeristet er en af forfatterne bag studiet.

[Translate to English:] Ph.d.-studerende Thor Haarh er en af forfatterne bag studiet.

A new Danish study sheds new light on why the success rate of fertility treatment can vary so much. In the study, the chances of becoming pregnant through IVF treatment were five times lower for those patients who had high concentrations of two bacteria that are markers for abnormal vaginal flora, compared to patients with normal vaginal flora.

The study has promising perspectives:

"If we know that by treating our patients for abnormal vaginal flora we can raise their probability of pregnancy to the same level as those with normal vaginal flora, then we will have taken a fantastic step forward. It has probably been very difficult to help these women to become pregnant until now,” says one of the authors behind the study, Professor Peter Humaidan from Aarhus University and the Fertility Clinic at the Regional Hospital Central Jutland in Skive.

About ten per cent of all Danish children are born as a result of assisted reproductive treatment.

The study has just been published in the international journal Human Reproduction.

A frequent condition
The abnormal bacterial flora are a frequent condition found in about 15 per cent of all Danish women. Among the fertility patients in the study, 28 per cent were found to have "abnormal vaginal flora" following tests using molecular biological methods. The group of women with an abnormal vaginal flora thus constitute a significant proportion of the women being treated for infertility.

"According to our study, it is clear that the vaginal bacteria reduce the pregnancy rate among IVF patients. The chance of pregnancy through IVF treatment was only nine per cent for women who had high concentrations of the bacteria Atopobium vaginae or Gardnerella vaginalis. By comparison, this figure was 44 per cent for the women who did not have the bacteria or who only had the bacteria in small quantities," says PhD student Thor Haahr, who has headed the study.

More knowledge needed

The samples from the survey are currently undergoing next generation sequencing analysis to provide an even better level of detail on the bacterial flora.

"We expect to learn more about which bacteria can be regarded as healthy and non-healthy in a reproductive context,” says Thor Haahr.

The study was carried out by researchers from the Fertility Clinic at the Regional Hospital Central Jutland in Skive, Aarhus University and SSI (Statens Serum Institut).

The research team now plan a randomised study in which women with abnormal vaginal flora either receive treatment with antibiotics supplemented with the 'good lactic acid bacteria’, lactic acid bacteria alone, or only a placebo.

"It is crucial that we find out whether giving antibiotics and/or supplements of lactic acid bacteria will actually help the chances of pregnancy, as it is not certain that you can remove the bacteria by antibiotic treatment alone," concludes Consultant Jørgen Skov Jensen from SSI (Statens Serum Institut).


About the study

  • A total of 130 women who were undergoing IVF treatment participated in the study.
  • The women were patients at the Fertility Clinic at the Regional Hospital Central Jutland in Skive and at Trianglen Fertility Clinic, Copenhagen.
  • The study was carried out in the period April - December 2014.
  • The study has been financed by the Moller Foundation for the Promotion of the Medical Sciences together with the Regional Hospital Central Jutland’s research funding programme.


Read more

Read the scientific article in Human Reproduction


 Further information

Thor Haahr, MD/PhD student
Aarhus University, Department of Clinical Medicine and
Fertility Clinic, Regional Hospital Central Jutland, Skive
Telephone: (+45) 2788 5402


Research, Health and disease, All groups, Department of Clinical Medicine, Health, External target group