Summary Objectives: The aim of study was to estimate the probability rates for unfavorable pregnancy outcomes in carriers of reciprocal chromosomal translocations involving 13 chromosome (RCT-13q). Material and methods: We collected total empirical data about 232 pregnancies of 56 carriers coming from 28 pedigrees. RCT classification was based on classic cytogenetic methods for interpretation of breakpoint position. The probability rates of particular type of pathology related to the total number of pregnancies after ascertainment correction have been calculated with the help of Stengel-Rutkowski and Stene method. Results: The risk figures for unbalanced offspring after 2:2 disjunction and adjacent-1 segregation for the whole group of pedigrees were calculated as 5.2+/-1.7% (9/173) – medium risk, for maternal (MAT) and paternal (PAT) carriers were about 6.2+/-2.3% (7/173) and 4.8+/-3.3% (2/42) respectively. Considering different segment lengths of 13q, similar values for shorter and longer segments were obtained [4.3+/-1.9% (5/115) for 13q21→qter and 7.0+/-3.3% (4/58) for 13q12→qter]. The risk figures for miscarriages as 36.4+/-3.6% (63/173) and for stillbirths/early death as 4.6+/-31.6% (8/173) were obtained. The risk figures for unbalanced offspring after 3:1 disjunction were calculated as 7.7+/-7.45 (9/13). Conclusions: 1. Risk figures for different pregnancy outcomes are differ among particular forms of pathology 2. Probability rate for unbalanced progeny at birth was calculated as a medium risk and similar values for carriers of different segments of 13q were obtained 3. Probability rate for miscarriages was high but risk for stillbirths/early deaths of newborn was low 4. No differences in values of rate for particular forms of pathology were found for maternal and paternal carriers of RCT -13q.