In 2016, more than 6 million women in the United States gave birth, transforming daughters into mothers and relationships into families.1 All patients are strongly encouraged to receive routine antepartum care with an obstetrician after pregnancy is confirmed. This includes laboratory tests, ultrasound and monitoring of the baby’s growth and activity, supportive measures to optimize nutrition and maternal comfort, and preventative therapy (including immunizations, smoking and alcohol cessation) to avoid untoward medication exposures and ensure a safe pregnancy.
A common question that arises relates to the safety of anesthesia and surgery during pregnancy. In general, all elective surgical procedures are typically postponed until at least several weeks after giving birth, to decrease both the risk to the mother as well as the unborn baby. Regardless, more than 75,000 pregnant females undergo surgery every year.2 Related risks can be broken down into 3 categories:
Risk to mother: Starting at week 6, significant changes in the maternal physiology occur in order to compensate for the baby’s developing circulatory system and nutritional needs. Increased blood volume leads to the heart working harder and faster. The lungs need to supply enough oxygen to meet the metabolic demands of a growing womb in an increasingly limited space. As the plasma or “water” component of the blood increases, the complex reactions that activate and eliminate our medications also change. The anesthesiologist must take these factors into account when planning an anesthetic for an emergency or urgent procedure.
Still, maternal risk for non-obstetric surgery is minimal and not significantly different than that of the general population. In a systematic review of more than 12,000 patients, a single death was reported.3 However, every patient should receive a thorough evaluation for factors related to “high-risk pregnancy,” characterized by significant cardiovascular, metabolic or other systemic changes that put the mother at risk during or immediately after pregnancy.
Risk to fetus: Between weeks 3 and 8, the baby’s organs start to develop from embryonic tissue implanted in the uterus. This is a critical stage with an intricate, orchestrated sequence of events, and any interruptions can lead to birth defects. A classification system exists to determine the safety of medications in pregnancy.4
Anesthetic medications have been studied extensively in pregnant females, with the vast majority of studies showing no difference in the incidence of birth defects compared to the general “background” risk of 3-5% after the first trimester.5 These same studies emphasize the importance of limiting exposure to the shortest possible duration, avoiding repetitive dosing, and waiting until after the first trimester. Prolonged exposure to anesthetic adjuncts such as benzodiazepines and nitrous oxide can lead to defects, and opioid medications such as fentanyl can lead to dependence and abstinence syndromes after the baby is born. All patients are strongly encouraged to discuss potential medication additions or changes with their obstetrician or primary care provider.
Risk to pregnancy: Even after the organs have formed and first heartbeat is heard, there is a slight increase in the incidence of ectopic pregnancy, miscarriage, and pre-term labor with pregnant patients receiving an operation. The rate of miscarriage is 5.8% after surgery, which is increased to 10.5% if surgery is performed during the first trimester.3 Severe changes in blood pressure, hypoxia (low oxygen), acidosis, and presence of infections are the most immediate causes associated with adverse outcomes.
For this reason, surgery is recommended to be performed in the 2nd trimester. Below are some precautions that are taken for female patients that are pregnant, or suspected to be pregnant, upon admission to the hospital:
- Determination of necessity and urgency: While elective surgery is postponed, urgent and emergent procedures are needed to ensure maternal well-being, which takes a priority over the fetus in the case of medical or surgical emergencies. For example, appendectomies (i.e. removal of the appendix due to infection and inflammation) are performed because the risk of severe infection (e.g. sepsis) or rupture would threaten the mother and fetus. Trauma and the resulting changes in blood pressure and sympathetic system activation can also compromise circulation to the fetus, and thus surgery must occur.
Anesthetic choice is relevant to avoid unnecessary exposure of narcotics to the mother and fetus, and a regional anesthetic (e.g. epidural, nerve block, local skin infiltration) can help achieve minimal risk.
- Routine pre-operative pregnancy tests: All female patients of childbearing age are typically required to take a urine pregnancy test as part of the pre-operative evaluation. If positive, a sample from the blood is taken to confirm pregnancy and estimate conceptual age.
- Fetal monitoring: Starting in the 2nd trimester, special electrodes and pads can be used to monitor the mother’s baby’s heart rate during surgery. In hospital settings, an obstetric consultant or team will be present to monitor fetal well-being and intervene if the pregnancy is deemed to be at risk.
- Emergency Protocol: Although CPR and similar life support measures are extremely rare, a strict protocol is followed for all pregnant female patients with unstable vital signs. The patient is tilted slightly to the left (“left uterine displacement”) to decrease the pressure exerted by the womb on the major blood vessels returning blood from the legs to the heart. If the patient is unable to breathe independently, airway access is obtained and supplemental oxygen is administered. In critical cases, intentional pre-term delivery of the baby can be undertaken to improve the outcomes of CPR.
References:
- https://www.guttmacher.org/united-states/pregnancy
- Goodman S. Anesthesia for nonobstetric surgery in the pregnant patient. Semin Perinatol 2002;26:136–145.
- Cohen-Kerem R, Railton C, Oren D, Lishner M, Koren G. Pregnancy outcomes following non-obstetric surgical intervention. Am J Surg. 2005;190:467-73.
- Content and Format of Labeling for Human Prescription Drug and Biological Products; Requirements for Pregnancy and Lactation Labeling (Federal Register/Vol. 73, No. 104/Thursday, May 29, 2008)
- Hoyert DL, Mathews TJ, Menacker F, et al. Annual summary of vital statistics: 2004. Pediatrics 2006;117:168–83.
