March 12, 2015 — Several recent studies have concluded that Zofran crosses the placenta in “significant amounts” and remains active in the fetus longer that it does in the mother, which raises concern about possible birth defect risks.
The first studies indicating that Zofran could cross the placenta were conducted in pregnant animals in the 1980s. Pregnancy outcomes included fetal deaths and birth defects.
Later studies confirmed that Zofran crosses the placenta in humans. According to one of most recent studies, published in Clinical Pharmacology & Therapeutics in December 2014:
“[Zofran] is characterized by rapid transplacental transfer and longer elimination half-life in neonates compared to their mother.”
Essentially, the researchers found that it passes very quickly from mother to fetus and remains active in the fetus much longer than it does in the mother.
In 2006, Clinical Pharmacokinetics published a study from Hong Kong that also found Zofran could rapidly pass to a fetus. Researchers found a “significant amount” of Zofran in tissue samples that were taken from 41 fetuses that were aborted surgically during the first trimester. All of the pregnant women were given three 8-mg doses of Zofran just before the surgery.