Mother-to-Child HIV Transmission Higher When Mother Has Other STIs

Having a second sexually-transmitted infection can significantly increase the chance that an HIV-positive pregnant woman passes the virus on to her infant.

Kristina Adachi, MD, MA

A new study confirms that HIV-infected pregnant women have a higher risk of transmitting the HIV to their infants if the mothers also have another sexually transmitted infection.

The research found the highest risk, by a significant margin, came when the mother was co-infected with cytomegalovirus (CMV).

Kristina Adachi, MD, MA, a clinical instructor in the Department of Pediatrics, Division of Infectious Diseases, at the University of California, Los Angeles, said the findings add to existing evidence that STIs can have adverse effects on pregnant women with HIV, and on their babies.

“In general, I think the study helped provide additional support for the idea that having STIs in pregnancy may increase the risk of HIV MTCT (mother-to-child transmission),” Adachi told MD Magazine. “There have not been many published studies that specifically looked at this relationship.”

Adachi and her co-authors tested 899 mother-infant pairs, checking the mothers for common STIs, and the babies for HIV. Nearly one third (30%) of the mothers tested positive for Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), Treponema pallidum (TP) and/or CMV at delivery. Among the infants, 9.1% tested positive for HIV.

HIV transmission rates varied depending on the specific infection found in the mother. Most prominent was the finding that when the mother tested positive for CMV, mother-to-child transmission occurred in 26.3% of cases. The next closest transmission rate was among women with Chlamydia trachomatis, of whom 12.5% passed HIV along to their infants.

Overall, 42% of HIV-infected infants were born to mothers with 1 of the 4 STIs, and women with an STI were nearly twice as likely to pass on HIV as women without an STI. The rates were highest among women with 2 of the 4 STIs.

Adachi is part of the HIV Prevention Trials Network’s HPTN-040 research group. She said previous research by the group has found associations between individual STIs and mother-to-child transmission of HIV, including chlamydia, syphilis and CMV viruria.

As for why the CMV association appears to be so strong, Adachi said the relationship between CMV and HIV is more complex than that of other STIs.

“The presence of CMV has the potential to impact the severity of HIV infection and viral replication and vice versa,” she said. “Specifically, it is thought that CMV may also lead to placental inflammation, which may facilitate HIV MTCT. In addition, CMV may also lead to upregulation of co-receptors that increase the likelihood of HIV infection.”

As far as the clinical implications, Adachi noted that Chlamydia, gonorrhea, and syphilis can cause other, even fatal, problems besides mother-to-child transmission, so it’s important that those STIs be treated in pregnant women generally, not just pregnant women with HIV.

“Unfortunately, at this time there are not good treatment options for primary infection with CMV in pregnancy,” she said.

Asked if treatment of STIs might result in a lower risk of mother-to-child transmission, Adachi said that specific question has not been studied extensively, but 1 study that did probe the issue found STI treatment improved pregnancy outcomes but did not affect mother-to-child transmission rates.

Adachi’s study is titled “Combined evaluation of sexually transmitted infections in HIV-infected pregnant women and infant HIV transmission.” It was published last week in PLOS One.

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