Over the last 30 years, interventional cardiology has emerged as a new therapeutic tool and an effective alternative to surgical therapy in several cardiac diseases, particularly valve stenosis and coronary artery disease. There is a lot of worry about the “real” fetal risk of radiation and contrast medium. The ionizing radiation can have harmful effects, which are cell death, teratogenic effects, carcinogenesis and genetic effects (mutations); however, these effects are not observed with the doses that are needed for the majority of diagnostic and therapeutic procedures. The effects of radiation on the fetus depend on the maternal radiation dose and gestational age at which the exposure occurs. The maximal permissible dose of radiation to the pregnant woman has been set at 50 mGy (www.​bt.​cdc.​gov/​radiation/​prenatalphysicia​n.​asp). The effect of radiation during pregnancy can be divided into three main phases. Irradiation during the preimplantation period (0–9 days) tends to cause death rather than anomalies. The effect appears to be “all or none.” The incidence of spontaneous embryo resorption during the first 2 weeks of gestation is approximately 25 %, and a dose of 100 mGy is estimated to increase the number by 0–1 %. During the period of active organogenesis (9–42 days), radiation causes severe structural anomalies. A dose of 2000 mGy will produce a 100 % incidence of congenital abnormalities, whereas a dose of 100 mGy results in 1 % increase in malformations over a baseline of 5–10 %. During the second and third trimester, risks are primarily related to the development of childhood leukemia and other malignancies. It has been estimated that a dose of 10 mGy increases the risk of childhood cancer by two cases per 100,000 births to a total of six cases in 100,000 live births. It has been calculated that the radiation dose to the mother for the most frequently performed cardiac percutaneous intervention (mitral balloon valvuloplasty and coronary angioplasty) are <20 mGy. Even though the risks are small, the interventional procedures have to be performed with forethought and care to minimize the radiation levels using the ALARA principle (as low as reasonably achievable). Maneuvers to minimize radiation are: (1) use echo guidance when possible, (2) place the source as distant as possible from the patient and the receiver as close as possible to the patient, (3) use only low-dose fluoroscopy as we learned from the total chronic occlusion procedures, (4) favor anteroposterior projections, (5) avoid direct radiation of the abdominal region, (6) collimate as tightly as possible to the area of interest, (7) minimize fluoroscopy time, and (8) let the procedure be done by experienced cardiologist. Abdominal shielding (placement of lead apron between the patient and the table) is recommended, although this lowers the dose to the fetus by only 2 %, paying particular attention to avoid the presence of lead in the field of the primary beam (systems automatically adjust the emitted radiation via an automatically modulatory system allowing a constant image quality; in these conditions, the presence of lead would increase scattered radiation). The best time for performing percutaneous intervention procedures is considered to be the fourth month, during which period organogenesis has been completed, the fetal thyroid is still inactive, and the volume of the uterus is still small so that there is greater distance between the fetus and the chest than in the following months. Monitoring and recording of radiation exposures is important to enable future assessment of possible effects on the fetus. These data should be included in the patient’s medical record or the procedure report [2].

Mitral valve stenosis, almost always of rheumatic origin, is the most common (90 %) and important cardiac valvular problem during pregnancy, particularly in developing countries. Most of the women with severe, but also those with moderate, mitral valve stenosis have worsening of their symptoms in the second or third trimester of pregnancy. Percutaneous balloon mitral valvotomy (PBMV) or valve repair/replacement during pregnancy should be considered in patients with moderate or severe mitral valve stenosis and persistent symptoms despite optimal medical therapy. Open mitral valvotomy or valve replacement during pregnancy is rarely necessary and has virtually disappeared from the surgical repertoire because young women have pliable valves without too much calcification that are suitable for percutaneous balloon valvotomy. This technique has been taken over from surgical closed mitral valvotomy which has been carried out safely with excellent results since the 1950s. PBMV, since the initial description by Inoue in 1984, has been shown to be successful in large studies of patients with symptomatic mitral stenosis. The mechanism of PBMV –commissural splitting – is similar to that of surgical valvotomy. This procedure has given good results, especially in young patients with noncalcified, thin valves without subvalvular thickening or significant mitral regurgitation. Dilatation of the stenotic mitral valve results in immediate hemodynamic improvement.

The mitral gradient generally decreases from 33 to 50 % of its initial value, and the cross-sectional area doubles. Both pulmonary capillary wedge pressure and pulmonary artery pressure decrease immediately, with the latter dropping further during the week after valvuloplasty. There are potential complications associated with this procedure, including atrial perforation resulting from transseptal puncture, cardiac tamponade, arrhythmias, embolism, mitral regurgitation, and hypotension. Mortality in the more recent series is reported to be 0.5 % [3]. Mitral regurgitation is the most common complication; in published reports its incidence varies from 0 to 50 %. Severe regurgitation is, however, uncommon and will occur only when there is structural damage to the mitral valve. The development or increase in the grade of mitral regurgitation is predicted by the presence of regurgitation and the severity of stenosis before the procedure. In patients with pliable valves, the development of mitral regurgitation is less frequent. Creation of a significant atrial septal defect secondary to septal dilatation has been reported to vary from 5 to 20 % and is hemodynamically insignificant in all patients. The long-term effect of these shunts is unknown, but it seems that most atrial septal defects close within 24 h.

Since 1988, more than 300 women are reported to have had PBMVs in pregnancy. In women with severe mitral stenosis and well-documented immediate clinical and hemodynamic results, the mean gradient across the stenotic mitral valve declined from the mean value of 21 to 5 mmHg, and the mitral valve area increased from the mean value of 0.9 to 2.1 cm². There have been no reports of serious maternal complications and only two fetal deaths. The reported incidence of mitral regurgitation is low, and in most cases it was only trivial or mild [4].

Balloon inflation generally causes transient maternal hypotension and a transient decrease in fetal heart rate. Both parameters return to baseline within a few seconds of balloon deflation, with no serious fetal distress noted. During balloon mitral valvolotomy, the supine position is necessary. This may cause maternal hypotension that can be alleviated by intravenous fluid infusion. The recumbent position causes pressure of the gravid uterus on the pelvic vessels, which may obstruct the passage of catheters. In the pregnant patient, the procedure has been performed with both the single and the double-balloon technique. Nowadays the use of single-balloon catheter is the preferred choice. Transesophageal ultrasonography or even simple transthoracic ultrasonography can be used during PBMV in order to minimize radiation exposure.

At the present, percutaneous mitral commissurotomy is preferably performed after 20 weeks gestation. It should only be considered in women with NYHA class III/IV and/or estimated systolic PAP 50 mmHg at echocardiography despite optimal medical treatment, in the absence of contraindications and if patient characteristics are suitable. In asymptomatic patients with mitral stenosis, the risk of maternal death during pregnancy and delivery is very low. However, the deterioration in hemodynamic conditions can be expected and emergency valvotomy may become necessary. A simple “rule of thumb” is an increase of one NYHA functional class any time during pregnancy. In these cases a “prophylactic” percutaneous mitral valvotomy should be considered, provided that there is a satisfactory echocardiographic score (<8).