A miscarriage is a relatively common event, representing about 10 to 20% of all known pregnancies, and it is defined as the spontaneous loss of a pregnancy before the 20th week (1). The causes of miscarriage could be that fetus is not developing as expected, underlying health conditions in the mother, or in late miscarriage also infections around the baby (1,2).
Several sexually transmitted infections (STI) and genital infections during pregnancy have been associated with miscarriage, for example, Neisseria gonorrhoeae, Chlamydia trachomatis, and Ureaplasma urealyticum (3). Testing for these organisms is very important among pregnant women, although unfortunately in some countries pregnant women are not routinely screened for U. urealyticum infection because this is not covered by insurance (4).
Vagianl infections can lead to spontaneous abortion, premature rupture of membranes, preterm delivery, intrauterine growth restriction, intrauterine death, neonatal infections, and postpartum infections (4).
Ureaplasma and Mycoplasma species remain the most commonly isolated infectious agents associated with preterm delivery and chorioamnionitis (4,5). Chorioamnionitis is the condition in which bacteria infect the membranes that surround the fetus and also the amniotic fluid, and can generate infections in the mother and the fetus (6).
In the case of U. urealyticum, this microorganism is part of the natural urogenital tract of healthy women, but it has also been found in almost half of the preterm cases. It is not completely clear why it can lead to miscarriage in some pregnancies, but it has been suggested that sometimes there could be an evasion of the local immune response, generating that U. urealyticum overgrows and invades the amniotic cavity only in some women (4,5). Afterward, the inflammatory process, endometrial infection, embryo-placental infection, and the toxic microbial byproducts could explain the miscarriages produced by the infection with U. urealyticum (5).
Hormonal and immunological changes occur normally during pregnancy, and the presence of specific vaginal bacteria can influence in obtaining different outcomes (4). For example, when U. urealyticum is found together with other microorganisms like M. hominis, there is an increased risk of severe adverse pregnancy outcomes compared to patients who were only positive for U. urealyticum (5).
It is recommended to test these microorganisms, especially in cases of recurrent pregnancy loss (RPL), so the doctor can indicate the correct treatment.
Mayoclinic. Miscarriage. https://www.mayoclinic.org/diseases-conditions/pregnancy-loss-miscarriage/symptoms-causes/syc-20354298#:~:text=Miscarriage%20is%20the%20spontaneous%20loss,even%20know%20about%20a%20pregnancy.
NHS. Miscarriage. https://www.nhs.uk/conditions/miscarriage/causes/#:~:text=If%20a%20miscarriage%20happens%20after,before%20any%20pain%20or%20bleeding.
Vallely, L. M., Egli-Gany, D., Pomat, W., Homer, C. S., Guy, R., Wand, H., Silver, B., Rumbold, A. R., Kaldor, J. M., Low, N., & Vallely, A. J. (2018). Adverse pregnancy and neonatal outcomes associated with Neisseria gonorrhoeae, Mycoplasma genitalium, M. hominis, Ureaplasma urealyticum and U. parvum: a systematic review and meta-analysis protocol. BMJ open, 8(11), e024175. https://doi.org/10.1136/bmjopen-2018-024175
Matasariu, D. R., Ursache, A., Agache, A., Mandici, C. E., Boiculese, V. L., Bujor, I. E., Rudisteanu, D., Dumitrascu, I., & Schaas, C. M. (2022). Genital infection with Ureaplasma urealyticum and its effect on pregnancy. Experimental and therapeutic medicine, 23(1), 89. https://doi.org/10.3892/etm.2021.11012
Celvalend Clinic. Chorioamnionitis https://my.clevelandclinic.org/health/diseases/12309-chorioamnionitis#:~:text=Chorioamnionitis%20is%20a%20condition%20that,both%20the%20mother%20and%20fetus.
Ahmadi, A., Khodabandehloo, M., Ramazanzadeh, R., Farhadifar, F., Nikkhoo, B., Soofizade, N., & Rezaii, M. (2014). Association between Ureaplasma urealyticum endocervical infection and spontaneous abortion. Iranian journal of microbiology, 6(6), 392–397.