The jury's out on whether viagra helps growth-restricted babies

27 March 2018
Premature baby

The jury’s out on whether viagra (or sildenafil) taken by mothers during pregnancy could help babies suffering from stunted growth in the womb by increasing blood supply to the placenta.

Fetal growth restriction, also called intrauterine growth restriction, is when a baby cannot grow properly due to problems with the placenta. It affects 5-10% of babies and can lead to stillbirth or to babies being born very small and at high risk of disabilities, developmental problems, as well as short-term and later illness.

Currently there is no treatment except early delivery, which can exacerbate those potential long-term problems.

The STRIDER NZAus trial involved 122 women in Christchurch, Wellington, Auckland and six Australian cities. Half took sildenafil and the other half took a placebo. The women and babies were closely monitored until surviving babies left neonatal units.

The researchers found no effect on growth in the womb, but did detect a trend towards higher survival of the babies in the sildenafil group before and after birth: 81 percent, or 51 out of 63 babies compared to 73 percent, or 43 out of 59 babies, in the control group.

They also found that 11 percent more babies in the sildenafil group survived free of major illness before leaving hospital, and fewer new cases of a serious pregnancy complication called preeclampsia in mothers after starting treatment (14 percent versus 23 percent).

Lead researcher Dr Katie Groom says: “Because of the small size of the study these differences are not statistically significant - this may mean this is simply a chance finding. However, if we saw the same differences in a larger group of mother and babies, this would be a very important difference, really having the potential to change lives in the future.”

The opportunity to explore the effect of this drug in a larger group is already underway. STRIDER NZAus is part of an international network of four trials across five countries. The STRIDER UK trial, led by the University of Liverpool, published its findings late 2017. It found that when sildenafil was given to pregnant women with severely growth-restricted babies, it did not prolong pregnancy, improve survival, or reduce short-term illness in the babies after birth.

“Babies in the UK trial were sicker and needed earlier delivery than the babies in our trial, so it is possible with more time available for the drug to make a difference that we may find a different result to this British study,” says Dr Groom, also an obstetrician and Maternal Fetal Medicine Subspecialist at Auckland City Hospital.

Results from the other two trials – across Canada and The Netherlands – are expected by the end of 2020.

The four trials are designed so that researchers will then be able to systematically pool the data, enabling more powerful and revealing analysis.

“Combining all four trial results should tell us with certainty whether our finding was real or chance, and whether or not to pursue sildenafil as a therapy for the future,” says Dr Groom.

Researchers are now assessing the development of the surviving babies from the Australasian and UK trials at the ages two to three years.

Dr Groom and Dr Chris McKinlay, a fellow researcher at the Institute and neonatologist at Middlemore Hospital, are leading the local follow-up study called the STRIDER NZAus Childhood Outcome Study.

“The results will tell us whether there are any longer term benefits of sildenafil that extend into childhood,” he says. “It will also give us valuable information about the health and development of babies born very small, which is really valuable information for parents.”

Viagra, which is more commonly used for male erectile dysfunction, captured the imagination of maternal and fetal researchers in the 1990s and promising early scientific evidence prompted the current trials.

"The theory behind our trials,” says Dr Groom, “is that Viagra dilates blood vessels in the male pelvis, increasing blood supply, so we wondered: could this drug also increase blood supply to the female pelvis and placenta?”

Dr Groom will present the findings at the Perinatal Society of Australia and New Zealand (PSANZ) Annual Scientific Congress 2018 on Tuesday 27 March, and at the Liggins Institute Public Lecture, “A Healthy Start to a Healthy Life”, on Wednesday 28 March, at the University of Auckland Fale Pasifika, 20 Wynyard Street.