Is Routine Preoperative Pregnancy Testing Necessary?

Introduction

Surgery on a pregnant woman raises several concerns. These include the effect of surgery and anesthesia on the developing fetus and the potential to trigger preterm labor. The hazards to the fetus could come from teratogenic effects of drugs administered during the perioperative period or, in a more advanced pregnancy, alterations in uteroplacental blood flow, as well as from maternal hypoxia or acidosis. It is reported that up to 15% of known pregnancies miscarry before 20 weeks, and up to 50% of unrecognized pregnancies miscarry during the first trimester. Because the period of organogenesis is during the first trimester, elective surgery is usually postponed to avoid potential teratogenicity and intrauterine fetal death. Although it is unclear which factors account for it, increased risk of spontaneous abortion is observed in women undergoing general anesthesia during the first or second trimester of pregnancy. Premature labor is more likely in the third trimester. Some studies have also suggested the presence of a strong association between central nervous system (CNS) defects and first-trimester anesthesia exposure.

Consequently, the issue of ruling out pregnancy before surgery is a crucial one. Unfortunately, medical history alone is often unreliable in ruling out pregnancy, especially in the adolescent female population. It is in this very population in which obtaining a routine pregnancy test may present an ethical and a legal problem. The patient may refuse to have the test done and may, in some states, have the legal right to keep that information private from her parents. On the other hand, the adult population of female patients of childbearing age may very well have the same or even a higher risk of unknown pregnancy before a surgical procedure. Routinely testing those patients for pregnancy may present a trust issue with women who believe that their history excludes that possibility. Moreover, calculation of the cost incurred if pregnancy screening is done routinely before each surgery adds to the controversy of the issue.

Options

Should preoperative pregnancy testing be performed on all female patients of childbearing age or just in select populations? Whether these select populations should include only those whose history is suggestive of pregnancy or whose history is unclear is still unresolved. The general practice of anesthesiologists differs according to the institutions in which they work, as well as by their personal judgments and convictions. Instituting policies for preoperative pregnancy testing should be based on the patient’s best interests in correspondence with state law and ethical responsibility.

The American Society of Anesthesiologists (ASA) Committee on Ethics has stated that patients should be offered but not required to undergo pregnancy testing unless there is a compelling medical reason to know that the patient is pregnant.

The ASA Practice Advisory for Preanesthesia Evaluation was amended by the ASA House of Delegates on October 15, 2003, to reflect this. “The Task Force recognizes that patients may present for anesthesia with an early undetected pregnancy. The Task Force believes that the literature is inadequate to inform patients or physicians on whether anesthesia causes harmful effects on early pregnancy. Pregnancy testing may be offered to female patients of childbearing age and for whom the results would alter the patient’s management.” The most common policies on preoperative pregnancy testing were outlined in a recent ASA newsletter. One approach is to test every female patient of childbearing potential regardless of whether she consents. The justification for this is that consent to surgery and anesthesia is also consent to a pregnancy test. An alternative policy is one that allows patients to refuse testing after anesthetic and surgical risks to a possible pregnancy have been explained. However, after refusal the patient is asked to waive all legal rights relating to undetected pregnancy. In some anesthesiology departments the patient is informed and consulted but may be tested regardless of whether she consents.

In a survey distributed to members of the Society of Obstetric Anesthesia and Perinatology (SOAP), almost one third of 169 respondents required preoperative pregnancy testing for all childbearing-age female patients through mandatory departmental policy. Of surveyed anesthesiologists, however, 66% required testing only when history indicated possible pregnancy. When surveyed, members of the ASA were asked whether pregnancy testing should be done routinely for all patients versus select populations; 17% believed it was a necessary routine test, whereas 78% chose the latter. The finding of a positive result has a very important impact on clinical management because it will lead to either delays or cancellations of surgery.

Evidence

Several studies have been conducted to examine the reliability of a preoperatively obtained medical history to indicate the possibility of pregnancy ( Table 5-1 ). These studies included patients from different age groups. One study by Malviya and colleagues in the adolescent population showed that none of the patients who underwent testing were found to have a positive urine pregnancy test. Data from the study indicated that most of the patients denied the possibility of pregnancy, whereas very few were not sure. The authors concluded that a detailed history should be obtained in all postmenarchal patients, and unless indicated by that history, pregnancy testing would not be required. It is noteworthy that 17 patients in that study refused testing.

TABLE 5-1

Detecting the Incidence of Pregnancy during Preoperative Evaluation Using History and Laboratory Testing

Study	Design	Duration	No. of Cases	Patient Population	Age in Years	Type of Test	Time of Test	No. of Positive Results	Correlation with History
Manley et al	Prospective	36 mo	2056	All females of childbearing potential	*	Urine or serum β-hCG	Within 6 days of surgery	Total 7 (0.3%)	No ^†
Gazvani et al	Prospective	23 mo	125	Females undergoing laparoscopic sterilizations	*	Urine β-hCG	*	Total 6 (5%)	*
Azzam et al	Retrospective	24 mo	412	Adolescents	10.5-20	Urine β-hCG	*	Total 5 (1.2%); <14 old: 0 (0%) ≥15 old: 5 (2.4%)	*
Twersky and Singleton	Prospective	*	315	All females of childbearing age	*	Serum β-hCG	*	Total 7 (2.2%) <23 old: 0	No ^†
Malviya et al	Prospective	26 mo	525	Adolescents	10-17	Urine β-hCG	Day of surgery	1 (questionable result; deemed negative)	Yes ^‡
Pierre et al	Prospective	21 mo	801	Adolescents	12-21	Urine β-hCG	*	Total 6 (0.49%)	No ^†
Wheeler and Cote	Prospective	15 mo	235	Adolescents and adults	10-34	*	*	Total 3 (1.3%); <15 old: 0 (0%) ≥15 old: 3 (2.3%)	No ^†
Hennrikus et al	Retrospective	36 mo	532	Adolescents	12-19	Urine β-hCG	Day of surgery	Total 5 (0.9%)	*
Kahn et al	Retrospective	12 mo	2588	All females of childbearing potential	*	Urine β-hCG	Day of surgery	Total 8 (0.3%)	No ^†