Zofran During the First Trimester: Does It Cross the Placental Barrier?

    In the wake of so many Zofran lawsuits, many women are even more confused about the effects of prescription drugs during a pregnancy. So many drugs prove to be beneficial before and after a pregnancy can cause serious damage to a developing fetus, and it can be difficult for doctors to determine what’s safe without extensive clinical trials. It leaves them asking one question: How do drugs cross the placental barrier, and what does that mean for a baby? One drug in question is Zofran, a drug taken to prevent morning sickness during the first trimester.

    If you took Zofran during pregnancy and your baby was born with a birth defect, speak to a Zofran attorney now. You may be entitled to financial compensation.

    What Causes a Drug to Cross the Placental Barrier?

    Researchers have known for a long time that babies could be affected by the drugs their mothers take—hence the direction to abstain from drinking alcohol while pregnant. It can be difficult to determine which prescriptions are safe for a woman to take while a fetus is developing, though. Not all drugs are the same and not all cross the placental barrier in the same concentrations. Furthermore, not all drugs that cross the barrier affect the development of the baby.

    In order to cause birth defects, a drug would have to cross the barrier relatively early in a pregnancy. The effect on the fetus is primarily determined by fetal age and the dosage of the drug. The first trimester is the most dangerous time for a developing baby, though some damage can be done during the final two as well.

    The placental barrier is a semipermeable layer of tissue in the placenta that serves as a selective membrane to substances passing from maternal to fetal blood. Whether a drug diffuses the placenta (and how much of it gets through) depends on a few main factors:

    • Fat solubility
    • Polarity (non-ionized tend to cross the barrier)
    • Protein binding
    • Molecular weight (measured in daltons) – drugs with low molecular weight typically cross the barrier

    Fetal pH is a little lower than that of the mother’s body, meaning that non-ionized drugs are trapped inside a fetus.

    Zofran and Birth Defects

    Zofran meets those qualifications, crossing the placental barrier relatively quickly. In a study performed by the Chinese University of Hong Kong, significant amounts of the drug were found in all embryonic compartments of an affected fetus, indicating significant amounts of placental diffusion during pregnancy. The drug concentration in the tissue itself was higher than that of the amniotic fluid, indicating that it did, in fact, get “trapped” inside the fetus after crossing the placental barrier.

    So what impact does Zofran have on a developing fetus? Swedish data suggests that Zofran causes an increased risk of congenital malformations—primarily holes in the heart. A subsequent nationwide cohort study further explored these risks, finding an increase in the prevalence of these heart defects in babies whose mothers had redeemed a prescription for the drug during their first trimester.

    An interesting thing about Zofran, however, is that its original indication was not for morning sickness. The drug was originally prescribed to treat post-operative and chemotherapy-related nausea. Clinical trials performed on pregnant women are few and far between, as the risk is too great to take on a developing fetus. As a result, doctors began unknowingly prescribing Zofran to pregnant women with serious morning sickness—with no knowledge of the potential side effects.

    In 2012, Zofran manufacturer GlaxoSmithKline paid $3 billion in settlement for illegal marketing in a case that involved Zofran, among other drugs. Unfortunately, women continue to come to the forefront with birth defect claims. One defect of particular concern is holes in the heart. While mothers are sometimes able to identify this problem at birth, many aren’t aware until their children are very ill or have a stroke—sometimes not until age 18 or later.

    What You Can Do

    If you or someone you know has taken Zofran during or immediately before her pregnancy, you may be eligible to file a lawsuit. It’s a good idea to speak with an attorney who’s familiar with mass torts of this nature so you might be more successful making your claim. Research regarding Zofran’s ability to cross the placental barrier dates back several years, meaning that you could have—and should have—been warned.


    1. “Ondansetron Use In Early Pregnancy And The Risk Of Congenital Malformations – A Register Based Nationwide Cohort Study.” Motherisk.org. Accessed March 31, 2015.
    2. “Drugs in Pregnancy.” Merck Manual Professional. Accessed March 31, 2015.
    3. “Pharmacology of the Placenta.” Open Anesthesia. Accessed March 31, 2015.
    4. “Placental Transfer of Ondansetron during Early Human Pregnancy.” National Center for Biotechnology Information. Accessed March 31, 2015.
    5. “GlaxoSmithKline to Plead Guilty and Pay $3 Billion to Resolve Fraud Allegations and Failure to Report Safety Data.” The United States Department of Justice News. July 2, 2012. Accessed March 31, 2015.

    Jared Heath

    Jared Heath is the author of The Sound in the Silence. In his role as an SEO content and digital marketing strategist, Jared was directly responsible for managing DrugJustice.com's editorial calendar and published articles on this website from 2015 to 2016. He is now pursuing a new career as a chiropractor.

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