Effects of common drugs on pregnancy.


EXPOSURE to medication during pregnancy is sometimes unavoidable, but many women don’t know that certain commonly used drugs can pose a risk to the foetus.

Bearing this in mind, internist Dr Jomo James has a few words of caution for expectant mothers about the use of medication during pregnancy.

“Avoid foetal drug exposure when possible in the first trimester, especially since it is the major period of development of the organs. But foetal exposure to drugs later in gestation can also result in subtle size, shape and structure of organ abnormalities, functional abnormalities, and impairment in growth,” he explained.

Below he lists some pain and fever medications which may have negative effects during pregnancy.



Dr James said acetaminophen is widely used for treatment of pain and fever with no high-quality evidence in humans of increased risk of pregnancy loss, congenital anomalies, or neurodevelopmental delay. But studies have reported an association between in-utero acetaminophen exposure and risk of attention deficit hyperactivity disorder (ADHD) behaviours in children from age seven to 11. Dr James explained, however, that the absolute risk was small, and that these studies have several methodological limitations including a lack of assessment of overall health for the index pregnancy, lack of information on acetaminophen strength and dosage units taken, and lack of formal assessment of ADHD.

Nevertheless, he cautioned patients against excessive use of acetaminophen.

“The therapeutic dose is 325 to 1,000 mg per dose in adults, with a usual maximum recommended daily dose of about three grams for oral immediate release preparations. Accidental overuse may be more likely in pregnancy due to limitations on the use of other medications and perceptions of its safety.”


Non-steroidal anti-inflammatory drugs (NSAIDs)

Dr James said the risks and benefits of using NSAIDs — like Ibuprofren — for treatment of pain or fever depends on the dose, gestational age, and duration of therapy. “Importantly, use of NSAIDs other than low-dose aspirin for more than 48 hours can cause in-utero constriction of the ductus arteriosus as early as 24 weeks of gestation, but is most common after 31 to 32 weeks,” he said.



“There is limited information on the effects of long-term greater than one month prescription opioid use during pregnancy. Neonatal withdrawal syndrome is a major concern when the mother has used opioids over the long term and in the week prior to delivery,” the internist said.

Opiods are painkillers such as morphine, methadone, Buprenorphine, hydrocodone, and oxycodone.


With regards to antibiotics without known teratogenic effects (agents that can disturb the development of the embryo or foetus), these include cephalosporins, penicillins, erythromycin (except the estolate), azithromycin, clindamycin, augmentin, and metronidazole.

The following antibiotics, according to Dr James, have been associated with known or potential agents that can halt the pregnancy or produce a congenital malformation:


1. Aminoglycosides

Dr James said these carry a risk of foetal (and maternal) ototoxicity and nephrotoxicity, but not with structural birth defects.


2. Doxycycline

The internist said doxycycline is avoided during pregnancy because other tetracyclines have been associated with transient suppression of bone growth and with staining of developing teeth, but available data does not show teratogenic effects from doxycycline.

3. Fluoroquinolones

“Fluoroquinolones are generally avoided during pregnancy and lactation because they are toxic to developing cartilage in experimental animal studies. However, neither adverse effects on cartilage nor an increase in congenital malformations from use during human pregnancy has been documented,” he pointed out.


4. Trimethoprim

Dr James said trimethoprim is generally avoided in the first trimester because it is a folic acid antagonist and has caused abnormal embryo development in experimental animals, and some case control studies have reported a possible association with a variety of birth defects. However, he pointed out that it is not a proven teratogen in humans, and additional evaluation of the safety of trimethoprim in human pregnancy is needed.

“The safest course is to avoid using trimethoprim in the first trimester if another antibiotic that is safe and effective is available. If exposure does occur, we advise patients of the baseline risk of birth defects in the population, and the possibility of a low but unproven increase in risk of birth defects after exposure to trimethoprim,” he explained.


4. Sulfonamides, nitrofurantoin

The safest course is to avoid using nitrofurantoin or sulfonamides in the first trimester if another antibiotic that is safe and effective is available. Both drugs have been implicated in causing haemolysis (rupturing of red blood cells) in women with glucose-6-phosphate dehydrogenase deficiency, a condition in which red blood cells break down when the body is exposed to certain drugs.


In relation to cold and allergy medications, Dr James said these usually fall into four broad categories — antihistamines for allergies, antitussives to help suppress coughs, expectorants to help bring up mucus, and decongestants to help relieve stuffiness.

“Bear in mind that most of these drugs are multi-symptom remedies, containing more than two to three different combinations of the above four categories. The antihistamines that are considered safe in pregnancy are Claritin, Zyrtec and Benadryl. Antitussives should generally be avoided in pregnancy; so, too, the decongestants — particularly pseudoephedrine and phenylephrine, especially in the first trimester. An alternative to these decongestants is the use of saline drops. A nasal spray such as the steroid budesonide is considered safe to use in pregnancy,” he said.

Again, when in doubt, it is best to get the advice of a doctor or pharmacist before using these medications, particularly as most allergy medications are dispensed over the counter and do not require a prescription.

Common cold and allergy symptoms can be treated with safe home remedies as an alternative to these forms of therapy.