STERILITY. – The term, related to that of impotence, is used in medico-legal language to indicate a particular defect in the efficacy of the procreative function.
Impotence and sterility present the concepts of two different defects and legal situations both in canon law and in civil law, while the capital importance of a clear delimitation of their respective objects is evident from the fact that the legitimacy and validity or nullity of marriage is linked to the demonstration of one or the other (“Impotence... diriment ipso iure matrimonium... Sterility neither diriments nor impedes marriage”: CIC, can. 1068). If, however, in common thought and language the difference in their respective conceptual content appears easily, on the juridical terrain, following the ideas of different currents and schools, it is not equally easy to draw a clear boundary between impotence and sterility. Their boundaries often overlap and almost vanish, exchanging parts of their content; thus, while the meaning of one expands, that of the other contracts, and the terminology becomes confused, not only in the comparison between civil law and canon law, but within the same legal system. For this question, see IMPOTENCE.
To maintain, therefore, an exact distinction of terms and thus avoid confusing sterility with impotence, it must be said that a person is sterile not when incapable of performing the conjugal act according to the natural order, but when capable of performing it, even though the effect of generation cannot follow from II. Therefore, the CIC establishes that sterility neither annuls nor impedes marriage (can. 1068 § 3); thus even persons of advanced age may contract marriage, provided they are able to consummate II. In other words: impotence exists when the capacity to consummate marriage is lacking; sterility exists when this capacity is not lacking, but the effect of that capacity is lacking, an effect that would not be lacking if its cause were found in those circumstances in which it could exercise all its power and produce the effect (generation) to which it is destined. In the case of impotence, the conjugal act cannot take place; in the case of sterility, the act can take place, but without its effect (cf. T. A. Iorio, *Theol. mor.*, III, 3rd ed., Naples 1947, n. 1061).
PHYSIOLOGICAL PERIODIC STERILITY (THE PERIODIC CONTINENCE METHOD ACCORDING TO OGINO-KNAUS-SMUL-DERS). – For various morbid causes that prevent the development, maturation, and regular progression of the ovum toward meeting the male sexual element, a woman may suffer from more or less continuous and lasting sterility. Apart from such conditions, the most recent studies have shown that a woman is periodically sterile even under perfectly physiological conditions, in relation to the periodicity of the maturation of the ova that develop in the ovaries. Such physiological periodic sterility can serve the purpose of birth control (see), according to the method of periodic continence.
1. Physiological periodic sterility as the basis of the periodic continence method
The period of time between the first day of one menstruation and the first day of the immediately following one constitutes in a woman the “sexual cycle,” in which not only the ovum and the uterus participate with characteristic phenomena, but the entire organism, including its higher psychic functions. With regard to the ovum, it concerns the periodic maturation of the ova, which occurs at determined, nearly constant times for each woman. The ova, preformed at birth and remaining in the embryonic state in the number of several tens of thousands, reach their maturation, normally one at a time, cycle by cycle throughout the period from puberty to menopause (see CLIMACTERIC AGE); thus only 400-450 ova become capable of fertilization over a period of about 30-35 years, the duration of a woman’s sexual life. For this reason, a woman is physiologically sterile before puberty and after menopause; she is periodically physiologically sterile in the periods between the maturation of one ovum and that of the next. With regard to the modifications affecting the uterus, it concerns the periodic destruction of the uterine mucosa (endometrium) at the close of each sexual cycle in which the ovum was not fertilized; a more or less abundant and prolonged hemorrhage (menstruation) is a clear sign of this, indicating that the intense proliferation and congestion of the uterine mucosa, preordained for the implantation of the fertilized ovum, was not utilized due to the failure of the fusion of the two sexual elements and the rapid death of the ovum.The appearance of menstruation thus becomes an easy external sign delimiting the end of one sexual cycle and the beginning of the next, and the non-utilization of the ovum.
Contrary to what was previously believed, when it was held that the release of the mature ovum from the ovarian surface (ovulation) occurred during the hemorrhagic phase of the cycle (Pouchet-Pflüger hypothesis, 1840, followed by the German gynecologist A. Capellmann in his *Medicina pastoralis*, Paris 1893), it is now firmly established that, under normal conditions, ovulation occurs around the middle of the cycle, if this has an average duration of 28 days, more generally between the 12th and 16th day preceding the start of the next cycle. The credit for this discovery and its demonstration goes to the Japanese Kyusaku Ogino and the Austrian Hermann Knaus, who, proceeding by different paths in successive years (1924-29), but unbeknownst to each other, brought to science the true chronology of ovulation. For the above reason, in view of the brief period of female fertility, which, in the span of the few days in which ovulation can occur, is essentially reduced to two hours or slightly more—the duration of the very short life of the ovum—there exist, for the remainder of the sexual cycle, before and after, at the beginning and end, two periods of physiological periodic sterility of unequal length. The pre-ovulatory or post-menstrual sterility period (from the first appearance of menstruation to the rupture of the Graafian follicle enclosing the ovum about to mature) comprises the phase of ovum development; the post-ovulatory or pre-menstrual sterility period will either be occupied by the meeting of the two sexual elements, fertilization, and the migration of the fertilized ovum toward uterine implantation, or, conversely, in it the death of the ovum that was not fertilized will occur, the vain expectation of the endometrium, which was ready to receive it and now, unused, begins its menstrual destruction. To these two phases of the cycle correspond two different endocrine orientations and balances (see ENDOCRINE GLANDS), which influence the entire bio-psychological equilibrium of the woman with both functional and structural modifications. While the first phase is under the influence of follicular secretion (folliculinic phase of the sexual cycle), the second is under the influence of the hormonal secretion of the corpus luteum (luteinic phase), which has formed in the empty cavity of the ruptured follicle. A higher regulation of this mechanism is linked to the anterior pituitary and the sexual nerve centers of the diencephalon.
The character and limits of this entry preclude a more extensive theoretical development and the scientific demonstration of the asserted facts, which can be drawn from the study of specialized works cited in the bibliography. For now, it suffices to say that based on the precise knowledge of the development of the female sexual cycle and the moment of ovulation, as well as the brief life of the ovum and the limited capacity for waiting and survival of the male sexual elements after their emission (spermatozoa lose motility, fertilizing capacity, and die after about 30–48 hours), it is possible to establish a system for birth control: the method of periodic abstinence, improperly called the “Ogino-Knaus method,” though it more rightly deserves the name of “Smulders’ method,” after the Dutchman J. M. J. Smulders (d. 1939), who, with skill and long patience from 1930 until his death, developed, disseminated, and verified it on the basis of the aforementioned scientific discoveries of Ogino and Knaus. He collected a large number of observations and practical experiences to make it ever more precise and reliable, and it can be said that all subsequent variations introduced by others do not substantially alter its foundations or the practical application of its substance.
According to Smulders, the method of periodic abstinence is founded on the following principles: 1) the ovum is mature and free, ready to be fertilized, only between the end of the follicular phase and the beginning of the luteal phase, and retains its vitality for only a very brief period (about 2 hours); 2) the fertilizing capacity of the male sexual elements does not exceed 30–40 hours; 3) the calculation of the woman’s fertile period must always be made backward from the probable date of the next menstruation, which, being an uncertain future event, can be provisionally determined by averaging the lengths of a certain number of past cycles. This is the most delicate and uncertain part of the method of periodic abstinence, upon which the skill of its defenders and promoters is focused, and against which most of the criticisms of its opponents are directed. If the length of the sexual cycle, though different for each woman, were a fixed constant for each individual, it would be easy and reliable to establish the recurrence of the few fertile days. On the contrary, each woman, though tending toward a certain cycle length (ranging from a minimum of 20–22 to a maximum of 34–36 days, with an average, according to Arey’s statistics based on 20,000 cycles, of 29 days), experiences fluctuations in her cycle period, which, following the characteristics of fluctuating variability, shift within margins of 2–5 days of difference. Later, it will be seen how, in applying the method, it is possible to account for the shifts that the fertile period undergoes due to the continuous oscillation in cycle length.
2. Technique of the method
By observing the variability of sexual cycles over a sufficiently long period (preferably 10–12 months), the maximum limits of their length fluctuations are established (for example, if the shortest observed cycle is 26 days and the longest is 30 days). This already entails the need to add a four-day margin (30–26 = 4) to the presumed fertile period of the woman, which is based on the five days within which ovulation can occur (the 12th, 13th, 14th, 15th, and 16th days before the next menstruation), plus two preceding days for the possible survival and waiting of spermatozoa (the 17th and 18th days), plus one more day (the 19th), as some propose, as an additional margin of caution against exceptionally early ovulations or longer sperm vitality, or, as others suggest, as a partial compensation for the inevitable hourly differences in determining the approximate start of the cycle. Altogether, this makes eight days during which conception could occur. In the example given, this results in a possible fertile period of 12 days (4 + 8), placed in the transition portion between the follicular and luteal phases of the sexual cycle. The placement of this period in the middle of the cycle leads to a fixed 5-day pre-menstrual period comprising the last 11 days of the cycle and a 5-day post-menstrual period between the start of the cycle and the 19th day (exclusive) before the next menstruation. While the 5-day pre-menstrual period always maintains a fixed length of 11 days, the post-menstrual period varies in length according to the different cycle length. For example, while for a 26-day cycle it will be 7 days (26–19 = 7), for a 30-day cycle it will be 11 days (30–19 = 11). Since the length of the next cycle is uncertain, the closest limit must be chosen provisionally, meaning the 5-day period should end on the 7th day, and the last 11 days of the 5-day period should be calculated based on the longest cycle. Thus, possible fertilization is considered from the 8th to the 19th day inclusive, counting from the start of the current cycle.Many objections have been raised against the method, some of which appear seriously to undermine its basis and the hoped-for results. The principal ones are as follows: extreme irregularity of cycles, particularly during certain periods of a woman’s life (climacteric, post-puberty, lactation, intercurrent illnesses, convalescence, etc.), making the fertile period very long and uncertain and correspondingly short and indeterminable the periods of safe abstinence; sudden physical and psychological traumas that disrupt the regularity of cycles; the possibility of supernumerary ovulations beyond the period established by Ogino and Knaus’s research—all circumstances that could undermine the reliability of the periods of physiological safe abstinence.
We cannot here enter into a detailed refutation of the above objections; however, it can be affirmed (see the specialized works cited in the bibliography) that the vast majority of women, particularly during the central period of their sexual life, are capable of excellent application of the method of periodic abstinence, even without recourse to specialized medical advice, provided they intelligently, accurately, and cautiously apply the rules set out in the best books on the method. Undoubtedly, there are cases and circumstances in which applying the rules becomes difficult or even impossible based solely on calendar methods: in such cases, the intervention of a specialist is required, who, through clinical study of the case and by carefully examining concomitant phenomena (intermenstrual crises, temperature curve, direct examination of the cyclic collateral phenomena of ovulation), employing the necessary means to restore any altered function, and tracking month by month the anomalies of rhythm and the random interference of perturbing factors, can succeed in making the method of periodic abstinence precise and reliable.
### 3. Statistical examination of the results.
The critical study of practical results represents the most probative element of the value of the periodic continence method; here, the experience of thousands of favorable cases, which are abundant in the statistics of honest and accurate experimenters, can be brought to bear. In contrast, opponents most often present only isolated cases, often not even personal ones, but lamentably studied, lacking the secure clinical elements on which a scientifically valuable critique can be based. To these, in addition to the data meticulously studied and described by Smulders, can be opposed the statistics of Miller, Schultz, and Anderson (*Conception Period in normal Adult Women*, in *Surg. Gynecol. Obst.*, June 1933, pp. 1020-25, Chicago); of Leo Lutz (*The Journal of the Amer. Med. Assoc.*, pp. 1241-46, Chicago 1935); of Carvalho Azevedo (*Das Problem der bewussten Befruchtung*, in *Ann. Brasil. Gynec.*, Rio de Janeiro 1936, pp. 255-83); of J. G. Holt (in *Ned. Tijdschr. V. Geneeskunde*, 1941, 8 Nov., no. 45); etc. A long observation of a married couple practicing the method for 17 years is also cited; despite this prolonged practice, only three conceptions occurred: one before the method was applied, and the other two (at intervals of 16 months and three and a half years) deliberately sought. Prof. C. G. Hartman of the Carnegie Institution of Washington, in *Birth Control Review* (May 1933), states, based on experience, that the periodic continence method, when properly applied, provides at least as much certainty as the most widely recommended contraceptive methods suggested by American marriage counselors.
Since these facts unfold on the biological plane and are thus subject to all the fluctuations of variability and the interference of all individual, social, and cosmological causes capable of continuously influencing the vital manifestations of the subject, there is no doubt that it is impossible to establish with absolute certainty, through a numerical index, the percentage of success for the method. For it, one can speak of 100% success, as well as 90% (Dickinson) or 80% (Dervaigne and Seguy), or even much lower percentages if the method is poorly applied or under particular conditions that only the method itself can assess and control (physical health of the woman, conditions of balance in her sexual, neurovegetative, endocrine, and higher neuro-affective functions). One can therefore conclude positively on the value of the periodic continence method and attribute the failures reported in some common cases to the aforementioned causes, outside the guidance of a specialized physician.
### 4. Moral question.
Without any doubt, the Church has always condemned all forms of neo-Malthusianism that aim to control births by vitiating the natural mechanism of the marital act (*V. NEO-MALTHUSIANISMO*). However, in reality, the periodic continence method cannot directly fall under such condemnations, since in it, apart from the voluntary choice of the periods of physiological sterility, the act is carried out according to the natural process, without the intervention of extrinsic elements that intrinsically vitiate II. For this reason, the morality and possible liceity of the acts performed depend less on the particular means employed than on the end the subject intends, the motives that drive them, and the circumstances in which it is practiced.
Now, provided that the subject uses marriage according to the natural order established by the Creator, they may do so even if the end does not coincide with the primary one (procreation), but rather with an objectively honest end or one that aligns with the secondary purposes of marriage (increase of mutual love, exchange of help, satisfaction of instinct, etc.). Such circumstances undoubtedly render the use of marriage generally licit, regardless of the period and even in circumstances where the woman is certainly sterile, such as during pregnancy and after menopause (*furthermore, the CIC, can. 1068, states: "Sterility neither dissolves nor impedes marriage."*)
However, some moralists (P. Salsmans in *Ephemerides Theologica Lovanienses*, 1934, pp. 562-70) argue that this cannot simply lead to admitting the liceity of periodic continence, since in it there exists the particular positive moment of choosing certain days and deliberately excluding others, with the aim of avoiding procreation; in this way, the hierarchical relationship of the ends of marriage would be altered, placing the secondary ends above the primary ones.
Yet, the majority of moralists (I. P. Gury-A. Ballerini, H. Noldin, A. Lehmkuhl, P. Gasparri, I. Ferreres, E. Génécot, J. Ubach, A. Vermeersch, F. Hürth, etc.) admit the liceity of periodic continence, which does not impair the object of marriage but only alters its subjective circumstances; thus, the matter of judgment regarding liceity becomes the intention, the motives that determine it, and the circumstances in which it is practiced (*cf. A. Vermeersch, Periodica de re morali*, 1934, p. 241).
In the past, two responses from the Sacred Penitentiary (1853 and 1880) should also be recalled; in them, it is stated that those spouses who limit the use of marriage to those periods in which conception is more difficult or impossible are not to be disturbed, provided they do nothing to impede conception.
However, every dissenting opinion among moralists must now be considered annulled in light of the clear and authoritative judgment repeatedly given by Pope Pius XII in his address to the participants of the Congress of the Italian Catholic Union of Midwives (29 Oct. 1951): *"If the application of the theory does not mean anything other than that spouses may make use of their marital right even on days of natural sterility, there is nothing to object to; in doing so, they neither impede nor prejudice in any way the consummation of the natural act and its further natural consequences... If, however, one goes further, allowing conjugal intercourse exclusively on those days, then the conduct of the spouses must be examined more carefully... If the limitation of intercourse to days of natural sterility is based solely on the use of the right... the moral liceity of such conduct by the spouses would have to be affirmed or denied according to whether the intention of consistently observing those times is based, or not, on sufficient and secure moral motives. The mere fact that the spouses do not violate the nature of the act and are even ready to accept and raise a child, who despite their precautions might be born, would not in itself suffice to guarantee the rectitude of*