Frequency of Rh phenotypes in relation to the outcome of pregnancy in the two groups of pregnant women

Lethal and sublethal genetical factors, including Rh factor, represent endogenous risk factors of the pregnancy outcome. These factors are most frequently inherited in recessive way and they often lead to the negative outcome of pregnancies. They represent pregnancy (a prirori) risk of various degrees. Inheritance of Rh system blood groups is linked to chromosome 1 and it could be explained by two alternative theories; molecular Rh system genetics has not yet been completely explained. The first formal-genetic theory postulates three closely linked gene sites (loci C, D and E) while the second theory has a monogenic character (one locus with several allele genes). Data on 755 pregnancies, which were (for various reasons) estimated as increased risk pregnancies, were registered at Gynaecology Clinic, Clinical Centre of University of Sarajevo, during the period from 1989 to 1992. These data were collected from pregnant women who, according to the certain indications from their familiar and personal anamnesis, demanded genetic consultations. The result of investigation of the basic Rh system phenotype distribution shows no statistically significant difference between monitored pregnant women. This result is assumed as valid for both pregnant women and their partners. The same result is suggesting that the observed increased risk pregnancy samples do not significantly differ from the previously studied population samples. Therefore, it has been concluded that Rh factor is not closely related to the increased risk of individual pregnancy outcomes, that is, it does not have relevant influence on the observed reproduction parameters. This result is very interesting and deserves particular medical attention and further evaluation in the future, particularly considering known immunological phenomena resulting from relations between reproduction partners belonging to the basic Rh system phenotypes.


Introduction
Lethal and sublethal genetical factors, including Rh factor, represent endogenous risk factors of the pregnancy outcome.These factors are most frequently inherited in recessive way and they often lead to the negative pregnancy outcomes.They represent pregnancy (a prirori) risk of various degrees.Inheritance of Rh system blood groups is linked to chromosome 1 (Thomson et al. 1991) and it could be explained by two alternative theories; molecular Rh system genetics has not yet been completely explained (Mouro et al. 1993).The first formal-genetic theory postulates three closely linked gene sites (loci C, D and E) while the second theory has a monogenic character (one locus with several allele genes (Vogel et Motulsky 1986).Both theories equally satisfy well known heredo-graphical facts regarding the Rh phenotype inheritance.Rh system phenotypes are usually divided to only two different phenotypes -phenotype Rh + and phenotype Rh -what has been particularly investigated in many population-genetic studies.The four most common alleles, that is, allele combinations have their total frequency percentage above 96% in different populations (Giblett 1983).Haemolytic disease in newborns and transfusion incompatibility are of particular medical importance and they are both related to the Rh blood factors.Recently, more attention has been paid to the other possible immune relations beside those seen in the biological reproduction processes in humans.For these reasons, the frequency of basic Rh system phenotypes in pregnancy samples has been recently more often investigated, not only considering eventual haemolytic disease appearance, but also regarding the pregnancy outcome and possible influence on the assessment of pregnancy risks.
Investigations of the frequency of Rh system phenotypes in population of Bosnia and Herzegovina are mostly sporadically carried out.This is also pertaining to the pregnancy samples classified considering their recorded outcomes (newborns, spontaneous abortions, artificial abortions).Comparative available data on pregnancy samples in Sarajevo region have also been considered (Babi} 1983and 1988, Red`i} 1996).
The objective of this paper-work was to stress the importance and specificity of the frequency of Rh system phenotypes in pregnancies with various risk degrees.Specific group genetic features of risky and unsuccessful pregnancies (grouped in accordance with applied medical treatments) were investigated.Individual belongings

Frequency of Rh phenotypes in relation to the outcome of pregnancy in the two groups of pregnant women
Amira Red`i}*, Fatima Begi}** *Department of Biology with Human Genetics, Faculty of Medicine, University of Sarajevo, ^ekalu{a 90, Bosnia and Herzegovina; E-mail: amira_redzic@yahoo.com**Cantonal Hospital "Irfan Ljubijanki}" Biha}, Bosnia and Herzegovina of pregnant women and their partners to the basic Rh system phenotypes were monitored.

Material and methods
Data on 755 pregnancies, which were (for various reasons) estimated as increased risk pregnancies, were registered at Gynaecology Clinic, Clinical Centre of University of Sarajevo, during the period from 1989 to 1992 (Red`i} 1996).These data were collected from pregnant women who, according to the certain indications from their familiar and personal anamnesis, demanded genetic consultation.Amniocentesis (sub-sample A1) was performed in 409 women while in other 346 women there were no indications for amniocentesis performance (sub-sample A2).The other observed sample included 480 cases of spontaneous abortions (sample E) registered at Gynaecology Clinic and in Sarajevo Health Centres during the period from 1992 to 1994 (Table 1).
Frequency of the basic Rh system phenotypes was determined in all mentioned samples.At the same tame, data on appropriate partners of the monitored pregnant women -potential fathers (if they were available) were also analysed.Previously published data on Rh blood type frequency among mothers of newborns (Babi} 1983) and among abortions (Babi} 1988), in the same population, were simultaneously presented and processed (Table 2).Statistically significant difference among studied (sub) samples of the examined material was estimated by the «t test» method (Garret, 1959), and the results were presented in Table 3.The same techniques were used for the eventual testing difference in relation to the other compared samples (Babi} 1983 and1988).

Results and discussion
The result of investigation of the basic Rh system phenotype distribution shows no statistically significant difference between monitored pregnant women.This result is assumed as valid for both pregnant women and their partners.The same result is suggesting that the observed increased risk pregnancy samples do not significantly differ from the previously studied population samples.Therefore, it has been concluded that Rh factor is not closely related to the increased risk of individual pregnancy outcomes, that is, it does not have relevant influence on the observed reproduction indicates.This result is very interesting and deserves particular medical attention and further evaluation in the future, particularly considering known immunological phenomena resulting from relations between reproduction partners' belonging to the basic Rh system phenotypes.

Samples
No  (Babi} 1983) and pregnant women sample during 1980-1981 (Babi} 1988) are also presented A1 -Amniocentesis-performed (AC) A2 -Amniocentesis-not performed Frequencies of Rh + phenotypes considering differences among the compared samples in relation to the various pregnancy outcomes were studied in the same way (Table 4).It was observed that our investigation samples did not significantly differ (according to statistics) from the analogue samples of the same or even broader population (Babi} 1983 and1988).
Haemolytic disease in newborns is not the only aspect of the Rh immunological relations between parents that influences on the parameter of significance for the reproduction investigations.It was found that various forms of Rh incompatibilities between partners were related to the frequency of (early) abortions what could be the subject of our future investigations.

Conclusion
On the account of the Rh blood factor distribution process in pregnancy samples of various risk degrees and various outcomes it is concluded that there are no statistically significant differences between pregnant women and their partners in all observed samples, as well as in comparison with the similar samples from a broader population.The conclusion is that Rh factor does not express relevant influence on the observed bio-reproduction parameters.

Table 2
Frequency of Rh+ phenotypes in observed samples (pregnant women and their partners)*

Table 1 .
General features and size of the observed samples

Table 3
Significance of the differences of Rh+ phenotype percentage frequency (t% test results)* in observed (sub) samples

Table 4
Frequency of Rh+ phenotypes in relation to the various pregnancy outcomes in observed samples (pregnant women and their partners)