We begin all communication by informing that all pregnancies start with a 4-5% risk for birth defects. This is the general population risk.
Tylenol PM is a combination of acetaminophen and diphenhydramine. Acetaminophen (Tylenol) is probably the most prescribed over-the-counter-drug in pregnancy. Acetaminophen is thought to work a little differently than other over-the-counter analgesics such as ibuprofen (Advil), naproxen (Aleve) or aspirin. Drugs such as ibuprofen reduce prostaglandins all over the body, reducing the inflammation that causes the pain or discomfort. Acetaminophen is thought to mostly work on prostaglandins in the brain, although the complete action of the drug is not well understood. Analgesics such as ibuprofen, naproxen and aspirin are not recommended in the third trimester of pregnancy due to risks for pulmonary hypertension in the baby, a potentially life-threatening condition. Acetaminophen has been studied in pregnancy, and no increased risk for birth defects or complications has been reported when used as directed by the manufacturer or physician.
Regarding the brand and dose, there is no recommendation to use any specific brand - you can use Tylenol or acetaminophen (generic)), and you can chose between regular strength, extra strength, etc. However, it is important to take the medication as directed by the manufacturer (read the label for instructions).
Diphenhydramine (Benadryl) is an antihistamine approved by the FDA in 1948 and has been used in pregnancy for allergies, insomnia, as well as nausea and vomiting in doses ranging from 25 mg to 200 mg per day.
The following studies have examined the prenatal affects of diphenhydramine: A 1974 study of children with oral clefts found a statistically significant association between first trimester use of diphenhydramine and cleft palate among 599 children with oral clefts and 590 controls. In contrast to this study, the Collaborative Perinatal Project that included 50,282 mother-child pairs did not find an increased risk for birth defects in 595 children with first trimester exposure to diphenhydramine and 2948 with exposure at any time. Additionally two separate studies published 1971 and 1985 found no association for birth defects with first trimester use of diphenhydramine.
Prematurity is birth that occurs prior to 37 weeks, and occurs in approximately 10-15% of pregnancies. Premature infants sometime require supplemental oxygen therapy because of the immaturity of their lungs. Premature infants who receive supplemental oxygen therapy are at risk to develop retinopathy of prematurity (also known as retrolental fibroplasia), which can potentially lead to blindness. A 1986 study has suggested that the use of antihistamines during the last two weeks of a premature delivery has been associated with an increased risk of retrolental fibroplasias in premature babies receiving supplemental oxygen therapy above what would normally be expected in premature infants receiving such therapy. The study found an incidence of 22% for retrolental fibroplasias as compared to only 11% of premature infants not exposed during this time.
In summary, the quality and the quantity of the data on diphenhydramine use in pregnancy is fair to good. Based on the available data we conclude that therapeutic doses of diphenhydramine during pregnancy do not pose an increased risk for birth defects, but the data are insufficient at this time to state that there is no risk. Women at risk for premature delivery may consider talking with their doctor about the reported risks for retrolental fibroplasia.
If you have additional questions and you live in California, we encourage you to call us at 800-532-3749 to receive a more complete response to your concerns. If you live in the U.S. but not California, please call 866-626-6847.