In recent studies, are done to know that if presence of microbiome have association with the diseases of pregnancy including preeclampsia (condition in which pregnant women have high blood pressure and fluid retention), small gestational age newborn, and preterm birth are correlates with the presence of microbiota in the placenta and defines the evidence of placental microbiota. They have done large cohort study of pregnant women who doesn’t bear offspring (nulliparous) and experiments are applied to give false positive result.
They studied two cohorts of pregnant patient, in first cohort, infant’s deliveries are done by C section, and 20patients include with preeclampsia condition, SGA newborn 20, and 40 patients in controls. Second cohort consist of preeclampsia condition 100 patients, newborn SGA 100, and preterm 100 patients and as well as used of twice number of controls to analyzed the result completely and effectively. These sample are then analyzed two times by using 16s RNA amplicon sequencing technique from two relatively different laboratory kits. The total biopsies of placenta include 537 women patients, in which 318 adverse pregnancy outcomes while 219 patients are in controls, by using different DNA extraction methods different conclusion are derived. Firstly, the bacterial sequencing done by using extracted DNA from Placenta is relatively low. Secondly, due to major laboratory contamination and used of reagent are major source of bacteria. Thirdly, the used of 16s RNA and metagenomics studies used to detect the very less amount of signals of bacteria residing in the placenta. Fourthly, tissue of placenta is contaminated with different microbes during deliveries, so the sample collection means placenta is contaminated. The only species that would present in the placenta before the onset of labor is S. agalactiae. This species is not act as part of batch effect (when non biological factor causes variation in the experiment), is was identified by the three different methods including 16s amplicon and metagenomics and PCR-qPCR techniques. So there is no significant association between presence of bacteria with disease like preeclampsia, SGA and PTB. The further explanation is that condition like preterm is associated with the presence of Ureaplamsa (greater than 1 percent), and it causes the uterine infection. So it concluded that microbiome in placenta is not a major cause of complication during human pregnancy. (Goffau, et al., 2019)
The presence S. agalactiae in placenta before delivery have clinical importance. The transmission of S. agalactiae from mother to infants is called perinatal transmission can cause the deadly sepsis in newborn baby. In united states different antibiotics are used by pregnant women against the S. agalactiae to prevent the death of the neonatal every year. More studies are required to know the association of organism in the tissue of placenta and the fetal and neonatal diseases. So there is no microbiome present in the placenta, bur during the C-section the bacteria from vagina moves into placenta. The different type of contamination occurs in the placenta, firstly the contamination during the deliver process, secondly the contamination during biopsy, thirdly the contamination during DNA extraction process, fourthly contamination by using reagents for amplification of DNA before the process of sequencing or lastly the contamination of laboratory equipment. (Goffau, et al., 2019)
Another studies to solve the controversy of presence of placental microbiome. The sample are collected from the women those have C-section deliver. The human and mouse sample are collected 28 humans placental sample and six murine placenta of mouse was under experimentation. All the human sample of placenta are amplified by using the 16s RNA gene. The human placenta is future analyzed by using gram staining, bacteria immunohistochemistry, electron microscopy and TaqMan RT-qPCR. And the mouse placenta is analyzed by 16s RNA gene amplification. The result was quiet interesting that none of placenta show the bacterial replication. None of these methods show the presence of any microbes in the placenta of human and mouse. Is it is said that fetal living environment like womb is sterile. (Kuperman, et al., 2020 Jan)