Australian researchers have found a 20% increased risk of birth defects, including kidney defects, in babies exposed to Zofran in the first trimester.
The study was published in BioMed Research International in December 2013.
The researchers found that babies exposed to Zofran in the first three months of pregnancy were 20% more likely to be born with a major birth defect, although the conclusions were based on a small sample sample size and non-significant.
The findings are backed up by two analyses of the same Danish registry of pregnancies. One analysis found a nonsignificant 12% increased risk of birth defects. Another analysis found a 30% increased risk, based on data from more pregnancies (nearly 900,000) over a longer period of time.
The Australian research team also found a possible sign of kidney defects. Zofran was linked to a 6-fold increased risk of malformations described as “obstructive defects of renal pelvis and ureter,” although the conclusions were imprecise and based on a small sample size. Obstructive defects often result in hydronephrosis, which can cause kidney failure.
Conclusions were based on nearly 100,000 births in Western Australia between 2002 and 2005. During that time, Zofran was used by 251 pregnant women. For unknown reasons, five times as many pregnant women used Zofran in 2005 compared to 2002.
Guidelines for Zofran’s use did not change during this time, but in 2013, GlaxoSmithKline (GSK) paid a $3 billion settlement for “off-label” marketing, including Zofran in pregnant women.