Currently, no scientific evidence has linked the anti-nausea drug Zofran, frequently prescribed “off-label” for morning sickness, to an increased risk of miscarriage. Then again, miscarriages can be caused by so many different abnormalities, that asking whether or not Zofran can cause a pregnancy loss may not be the right way of framing the question at all.
What Causes Miscarriage?
Most miscarriages occur very early in pregnancy. In fact, the term specifically describes pregnancies that end spontaneously within the first 20 weeks of gestation. Miscarriages can be caused by hormonal imbalances, maternal infections or other pre-existing medical problems, like diabetes. Notably, women with diabetes are also at an increased risk for delivering babies with birth defects.
Most miscarriages, up to 3 out of every 4, however, are what researchers call “chemical pregnancies.”
Researchers believe that most miscarriages are what they call “chemical pregnancies.”
Once an egg has been fertilized, usually inside the Fallopian tube, the resulting zygote travels to the uterus. A “zygote” is what we call the combination of egg and sperm, a single cell with 46 chromosomes, 23 from each parent. But by this point, that cell is dividing rapidly, and soon it comes to implant in the uterine wall.
Some of the zygote’s cells start producing human chorionic gonadotropin, or hCG, a chemical that kick-starts the production of progesterone, which makes the uterine lining thicker to support a growing embryo. hCG is what most pregnancy tests, including at-home urine pregnancy tests, check for, and that’s why these very early miscarriages are called “chemical” pregnancies. They show up on pregnancy tests, and many women will notice that their period is around a week late.
But something happens, usually because of a chromosomal abnormality, that either prevents complete implantation, or stops the process early on. Essentially, the dividing cells just make a mistake at some point, copying too many, or too few, chromosomes, and short-circuiting the pregnancy. This occurs before an ultrasound would have been able to confirm the pregnancy, by imaging a gestational sac surrounding the embryo, which is why “chemical” pregnancies aren’t considered “clinically-recognized” pregnancies.
How Common Is Miscarriage?
Of “recognized” pregnancies, ones confirmed by ultrasound or post-miscarriage tissue sampling, anywhere from 12% to 15% will end in a miscarriage, according to the University of California at Los Angeles. But for all conceptions, the proportion that end in a spontaneous abortion, another name for miscarriage, may be much higher. Some estimates put the actual rate of miscarriage as high as 60%.
Having a miscarriage does not, by any means, mean a woman will necessarily have another in the future. Women under 35 have around a 15% chance of miscarriage, regardless of individual factors. For women who have had a previous miscarriage, the chance of having another is about 25%, which is only a moderate increase over the 15% chance affecting all women. But the risk does increase with age. Over 45, the chances of having a miscarriage can be as high as 50%.
A Link Between Miscarriage & Zofran?
Since miscarriage is most commonly caused by chromosomal abnormalities, and dangerous drugs can have an affect on how embryonic cells divide, it’s not unreasonable to ask whether Zofran can cause miscarriage. For now, though, the research is scant on the link, if one exists, between the popular anti-nausea drug and spontaneous abortion.
Congenital abnormalities (birth defects) are a “major cause[…] of miscarriage and stillbirth,” according to About Health. That may be relevant, since the ingestion of Zofran during early pregnancy, when a fetus is just beginning to form, has been linked to an increased risk for several serious birth defects, including “hole in the heart” defects and cleft palate.