Anesthesia and Pregnancy

© G.M. Woerlee

A pregnant woman will come into contact with anesthetic drugs while working in an operating theater, or if she requires a surgical procedure under anesthesia during pregnancy. These situations raise three questions.

1. What are the effects of trace concentrations of anesthetic gases in the air of the operating theater upon the developing fetus of a pregnant woman who works there?
2. What are the effects of anesthesia administered to a woman during pregnancy upon the woman and her unborn child?
3. What are the effects of surgery performed upon a woman during pregnancy and her unborn child?

Anesthetic gases in the operating theater and pregnancy

Many people, and especially women working in operating theaters, are concerned about the effects of trace concentrations of anesthetic gases in the air of operating theaters on a pregnancy. They are especially worried whether these trace concentrations of anesthetic gases increase their chances of miscarrying, ectopic pregnancy, stillbirth, or giving birth to an abnormal child. All these things are extensively discussed, together with statistical data, on the page in this website called Anesthetic Gas Pollution in the Operating Theater.

Anesthesia and surgery during pregnancy

People never undergo anesthesia without subsequently undergoing a surgical procedure - people undergo anesthesia to make a surgical procedure possible. So the effects of anesthesia on a pregnant woman and her unborn child are actually the combined effects of anesthesia together with surgery.

Up to 2% of all pregnant women require surgery for all manner of conditions unrelated to their pregnancy, e.g. appendicits, broken bones, etc, etc, (Ne Mhuireachtaigh 2006). Surgeons perform these non-obstetrical operations upon pregnant women only for serious conditions threatening the life of the mother, or conditions causing serious disability if not performed at that moment. The normal policy is to wait until after delivery of the baby before performing any non-urgent surgery. So what are the statistics regarding anesthesia and surgery performed during pregnancy?

• Maternal death rate as a result of anesthesia and surgery is low, comparable to those for non-pregnant young women (Cohen-Kerem 2005, Kuczkowski 2004, Ne Mhuireachtaigh 2006).
• Regional or general anesthesia is administered for a short time, and anesthetic drug concentrations in the body of the mother and unborn child are minimal within minutes to hours. Undetectable, or trace concentrations of these drugs are present in the body of the woman and her unborn child at the end of 24 hours, and even these are eliminated from their bodies after a day or two. So the chance is minimal that anesthetic drugs cause birth defects, otherwise known as fetal abnormalities, or teratogenic effects (Ne Mhuireachtaigh 2006, Kuczkowski-2004). Studies of the babies of the more than ten thousand pregnant women who underwent anesthesia and surgery reveal that the chance of these women delivering a baby with a birth defect varies between 2-3.9% (Cohen-Kerem 2005, Duncan 1986), which is comparable to the normal chance of delivering a baby with a birth defect (see tables on the web-page Anesthetic Gas Pollution in the Operating Theater).
• The chance of miscarriage or fetal death as a result of anesthesia and surgery is about 5.8% when averaged over all pregnancy trimesters, but is about 10.5% when anesthesia and surgery occur during the first trimester (Cohen-Kerem 2005). This is a much higher chance of miscarriage than normal (see tables on the web-page Anesthetic Gas Pollution in the Operating Theater). So anesthesia and surgery are associated with a higher fetal death rate than normal.
• The chance of premature labor occurring as a result of anesthesia and surgery is higher than normal at about 8.3% (Cohen-Kerem 2005, Duncan 1986)

Concluding remarks

The conclusions drawn from these statistics are evident. Anesthesia and surgery during pregnancy is safe for the mother, and the chance of delivering a baby with a birth defect is unchanged by anesthesia and surgery. However, anesthesia and surgery performed during the first trimester of pregnancy is associated with a high rate of infant death, while anesthesia and surgery can induce premature labor when performed in later phases of pregnancy. So any decision to perform an operation during pregnancy, is determined by weighing the necessity for performing the operation against the higher than normal rate of fetal loss and prematurity.

© G.M. Woerlee | last updated 5 August 2009