A recent study showed that pregnant women who take certain types of painkillers, including aspirin, are up to 80% more likely to miscarry. Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most widely used drugs in the developed world and are often used by pregnant women. Because of the medications’ widespread use, any unintended effect could have serious adverse public health consequences. This topic is pertinent for women with spondylitis who are pregnant or wish to start a family.

Who They Studied
To evaluate whether prenatal use of NSAIDs is associated with increased risk of miscarriage, researchers in the San Francisco area recruited and interviewed 1055 pregnant women immediately after their positive pregnancy tests. The average gestational age, which is the period of development in the uterus from conception until birth, at entry to the study was 40 days. The women were asked about their reproductive history and their use of painkillers (NSAIDs, aspirin, paracetamol).

They defined NSAID users as those who reported using ibuprofen or naproxen or preparations containing those drugs (Advil, Motrin, Naprosyn) after their last menstruation.

They defined aspirin users as those who reported using aspirin or preparations containing aspirin (baby aspirin, Alka Seltzer, Excedrin, Soma) after their last menstruation.

They defined paracetamol users as those who reported using paracetamol or preparations containing paracetamol (Tylenol, Tylenol Cold, Tylenol Sinus, Tylenol with codeine, Tylenol PM, Theraflu, Triaminic, Vicodin) after their last menstruation.

To avoid the possibility that the condition for which NSAID or aspirin was taken might cause miscarriage, they excluded seven women who reported cramping as the reason for taking the medication since cramping could be an early sign of miscarriage.

Findings

• 149 of the 980 (15%) women who did not use NSAIDs had a miscarriage
  
• 13 of the 53 (24.5%) women who reported prenatal NSAID use around or during pregnancy had a miscarriage

Prenatal NSAID use was associated with an 80% increased risk of miscarriage. The association was stronger if the initial NSAID use was around the time of conception or if NSAID use lasted more than a week.

Prenatal aspirin use was similarly associated with an increased risk of miscarriage (60% higher than nonusers).

Yet prenatal use of paracetamol (which is pharmacologically different from NSAIDs and aspirin) was not associated with an increased risk of miscarriage regardless of timing and duration of use. Paracetamol, aspirin, and other NSAIDs (like ibuprofen) suppress fatty acids that are needed for the successful implantation of an embryo in the womb; while NSAIDs act on the whole body, paracetamol acts only on the central nervous system. This may help explain why it has no effect on pregnancy, according to the researchers.

Further Studies Needed
The researchers say that additional research is needed to examine the apparent association between prenatal use of NSAIDs and aspirin and an increased risk of miscarriage.

“These findings will need confirmation. Meanwhile, it may be prudent for physicians and women who are planning to be pregnant to be aware of this potential risk and avoid using NSAIDs around conception,” states the authors of the research.

Lead researcher, Dr. De-Kun Li (a Kaiser Foundation research scientist) hesitates to give advice to women on the basis of this study because more work is needed to prove a cause-and-effect relationship. He says that it is sound medical practice for women with chronic conditions that require the use of NSAIDs to discuss what to do before and during pregnancy with their doctors. Other women would do well to use acetaminophen for headaches and other minor pains.

Other studies have shown that pregnant women who took low-doses of aspirin were less likely to have a still-birth or develop pre-eclampsia, the life-threatening condition.

A spokesperson for the American College of Obstetrics and Gynecology says the organization has not taken a stand on the issue.