Defining Paternity

Mar 11

The mitzvah of Pru U’rvu—to be fruitful and multiply—is a cornerstone of Jewish life and the very first commandment in the Torah (Bereishit 1:28). Yet, fulfilling this mitzvah has long been fraught with challenges.

According to the World Health Organization (2023), approximately 17.5% of married couples experience infertility, with around 30% of cases attributed to male factors and the remaining 70% to female or combined causes. While modern fertility treatments have brought new hope to families yearning for children, they also introduce a host of complex halachic questions. Given the novelty of these technologies and the lack of direct precedent, poskim have grappled with applying traditional principles to unprecedented scenarios, many of which touch upon multiple, intersecting areas of Jewish law.

Biologically, the creation of a child occurs in three primary stages: conception, gestation, and birth (parturition). Each of these stages, when influenced by medical intervention, presents distinct halachic challenges. In this discussion, we will begin with the first stage—conception—and the halachic questions that arise when artificial methods are used to facilitate fertilization.

The natural process of conception involves the union of male and female genetic material within the reproductive tract. However, fertility treatments such as intrauterine insemination (IUI) can bypass parts of this natural process. IUI is commonly employed in cases of mild male-factor infertility, where sperm count or motility is suboptimal, or in cervical-factor infertility, where cervical mucus impedes sperm from entering the uterus. In such cases, sperm is directly introduced into the uterine cavity, increasing the likelihood of fertilization when natural conception proves difficult.

While a full review of the clinical science behind fertility treatments is beyond the scope of this discussion, any meaningful ethical or halachic analysis must begin with a solid grounding in the medical foundations. (For an accessible and up-to-date overview, see Santoro & Polotsky, 2025.)

Acquiring Male Fertility Factor

The first halachic issue that arises in fertility treatments concerns acquiring the male fertility factor (sperm). There is significant debate among poskim (halachic authorities) on whether extracting sperm for this purpose constitutes a violation of the prohibition against zera levatala (wasting seed).

The Divrei Malkiel was one of the first authorities to address this issue. He ruled that it is forbidden as the act of extraction itself is inherently purposeless and does not become permissible merely because it is later used for fertilization. Furthermore, he argued that there is no guarantee the sperm will be successfully utilized, and if the insemination fails, the act of extraction retroactively becomes purposeless. He also highlighted potential risks, such as accidental mixing of the husband's sperm with foreign sperm. Similar sentiments are found in other poskim (Mishpetei Uziel EH:19, Yaskil Avdi Vol 5 EH:10).

Notwithstanding, the majority of poskim hold that retrieving sperm for fertility treatments does not necessarily violate the prohibition of wasting seed. The Beis Yitzchak (vol 1 Siman 50) asserts that artificial insemination or conception through indirect means fulfills the mitzvah of Pru U'rvu if no seed is wasted. Based on Tosafot (Sanhedrin 59b), he explains that zera levatala is perhaps the inverse of the Pru U'rvu. Thus, successful conception through such methods fulfills both the mitzvah and avoids waste. Similarly, other authorities (Yabia Omer ח" ב חאבהע" ז, Igress moshe חאבהע" ז ח" א סי' עא, Rabbi Shlomo Zalman Auerbach Noam, 1958, pp. 145–166), maintain that sperm extraction for the purpose of fulfilling the mitzvah is permissible when handled appropriately. (For the Rebbe’s stance, see journal Assia, Volumes 61–62, 1998, p. 47)

Artificial Insemination and Pru U'rvu

The Chelkat Mechokeik (Even HaEzer 1:8) raises the question of whether a man is considered the halachic father if his child is not conceived through a sexual act. Specifically, the debate centers on whether fatherhood is established simply by providing the male genetic material or if a penetrative sexual act is also necessary to create a paternal relationship. While this question may seem unusual by modern standards, Halacha does not always equate the transfer of genetic material with parental status. For example, a ger (convert) is halachically considered unrelated to their biological family after conversion, even if the entire family converts together. Similarly, a non-Jew who fathers a child with a Jewish woman is not regarded as the halachic father (Mishneh Torah, Mamrim 5:9–11). The Chelkat Mechokeik suggests that without a sexual act, the donor of genetic material cannot be considered a legal father, effectively rendering the child fatherless. This position was taken by a minority of modern Poskim chief among them the Tzitz Eliezer (Vol. 9, 51:4:1,8).

In contrast, the Beit Shmuel (Even HaEzer 1:10, based on the Bach, Yoreh De'ah 195) argues that paternity can be established without sexual intercourse. A case in the Gemara (Chagiga 15a) discusses a man who deposited his semen in bathwater, which later entered the womb of a woman who bathed there, resulting in conception. This story is echoed in the legend of Ben Sira, who is said to have been conceived when the prophet Yeremiah's daughter became pregnant through his semen in a bath. Initially called "Ben-Zera" (Son of Seed), he later changed his name to "Ben-Sira," corresponding to "Yeremiah" in gematria. This account is mentioned in Likutei Maharil (Siman 5) and Teshvot Tashbetz (Vol. 3, Siman 263). Further support for this view comes from Rabbeinu Peretz, as quoted by Bach and Beit Shmuel, who ruled that a woman should not lie on sheets previously used by another man lest she conceives. This ruling implies that genetic material alone, without intercourse, can confer paternity, highlighting the risk of a child unknowingly marrying a sibling.

This latter position is taken by the vast majority of poskim, including Rav Shlomo Zalman Auerbach (Nishmat Avraham, Even HaEzer 1:5) and Rav Moshe Feinstein (Igrot Moshe, Even HaEzer Vol. 1, 10, 71), who rule that the donor of genetic material is the halachic father of the child.