Possible benefits of using aspirin during pregnancy

Aspirin is one of the most commonly used over the counter drugs and is used for such diverse conditions as mild to moderate pain like headaches or menstrual cramps, mild to moderate arthritis and other inflammatory conditions, and as a blood thinner to prevent inappropriate clotting of blood that could cause thromboses, heart attacks and stroke. The use of aspirin during pregnancy is controversial and generally discouraged unless specific health conditions in the mother exist so that the benefits of using a low dose aspirin regimen outweigh possible risks that will be described in more detail below.

Studies have shown that low-does aspirin during pregnancy can reduce the risk for having a premature birth in women who have several risk factors for premature births, like having had a premature birth or preterm labor in the past or having diabetes or high blood pressure. A French study in women taking low dose aspirin during pregnancy to prevent premature birth showed that the children of these women had fewer problems five years after birth than the children of women who had not taken low-dose aspirin during the pregnancy.

Low dose aspirin during pregnancy is also often prescribed for women who have risk factors to develop a pregnancy associated disease that is called preeclampsia and that causes the blood pressure to rise to unsafe levels and also damages the kidney. This condition can advance to a potentially fatal disease for both mother and child that is called eclampsia. Risk factors for developing preeclampsia during pregnancy are having had preeclampsia in a prior pregnancy, diabetes, kidney disease, and chronic high blood pressure. Although studies have shown that some women at risk for preeclampsia can benefit from taking low dose aspirin during pregnancy, there is controversy about which women are the best candidates for this therapy, when it should start, and how long and how much aspirin should be taken.

Other health conditions for which low dose aspirin are prescribed are conditions that come with an increased risk for blood clotting or thrombosis. These conditions can include women who have lupus and produce a blood clot producing antibody that is called lupus coagulant or women with a related disease called antiphospholipid syndrome


Possible risk of using aspirin during pregnancy

Despite the fact that there are studies that show that low dose aspirin can be beneficial for certain conditions, use of aspirin, in particular at the regular adult strength is associated with considerable risk for both the mother and the baby. This is the reason why the U.S. Food and Drug Administration (FDA) issued a warning in 1990 that said the following about the use of aspirin during pregnancy: "It is especially important not to use aspirin during the last three months of pregnancy, unless specifically directed to do so by a physician because it may cause problems in the unborn child or complications during delivery."

Aspirin is also included on the list of the California Environmental Protection Agency (CAL/EPA) Proposition 65 of developmental toxins (CAL/EPA Proposition 65 List). This listing means that an expert panel of scientists agreed that there is enough evidence to believe that this substance can harm unborn babies. This does not necessarily mean that aspirin taken at a low dose for a specific health condition during the harms the baby in any case, but there are several mechanisms how aspirin can cause problems during pregnancy, especially in the last trimester. Aspirin and other non-steriodal anti-inflammatory drugs or NSAIDs work by inhibiting the synthesis of a certain family of inflammatory messenger molecules called prostaglandins. Prostaglandins, however, have also other functions in the body. One of the functions for example is the regulation of production of the mucus in the stomach that protects the stomach wall from the acid in the stomach. This is the reason why taking aspirin over a long time can cause stomach problems. In unborn babies, a drop in prostaglandin production happens during birth and is the signal to reroute the blood circulation to use the lung instead of the placenta as the source of oxygen. Taking a regular adult dose of aspirin during the last trimester of the pregnancy can cause a drop in prostaglandin production in the baby’s body and can thus cause the rerouting of the blood supply prematurely in the uterus. This can be fatal to the baby. There have also been studies that show that taking aspirin at the time of the conception or in the first weeks of the pregnancy is associated with an increased risk of miscarriages. Nevertheless, there have been other studies that did not find this result, and therefore it is still under debate whether aspirin can increase the risk of miscarriages. Since aspirin can inhibit blood clotting and works as a blood thinner, taking aspirin during pregnancy can increase the risk of bleeding problems during the delivery. However, taking low dose aspirin to decrease the risk of premature birth in women with risk factors for premature birth, did not increase the babies risk for bleeding in the brain in a French study. Bleeding in the brain is a condition premature babies often suffer from. Aspirin can also delay labor. This is one of the reasons why it is used for women with a high risk of premature birth, but this can cause problems in women that are full term. Aspirin is associated with a condition in children that is called Reye’s syndrome. This disease which causes are not entirely understood can damage many organs of the body, in particular the brain and the liver. It can be fatal and children taking aspirin have an increased risk of developing Reye’s syndrome. It is not known whether the risk for the baby of developing Reye’s syndrome after birth is increased, if the mother has taken aspirin during the pregnancy, but since aspirin is passed into the milk taking aspirin while breast feeding is strongly discouraged.