Does the halacha consider a prematurely born child, or a full term child whose hair and nails are underdeveloped, a legal person with rights and obligations? This question has many applications and the answer differs depending on the context in which it is asked.
A person who kills a prematurely born child before the thirtieth day of its life is not liable to capital punishment under Jewish law. A fully developed but prematurely born child who died within hours after birth has rights of inheritance. The melachah involved in surgery is permitted on Shabbat in connection with the circumcision of an eight-day-old fully developed but prematurely born child The laws of aveilut, mourning for the deceased, do not apply to a prematurely born child that did not survive thirty days.
If a man dies childless, the Torah commands the deceased’s brother to marry his brother’s widow in a ceremony known as yibum, or to perform a special form of divorce ceremony with her known as chalitzah. What does “childless” mean in the yibum context? Clearly, if the deceased is survived by a fully developed full-term child born moments after his death, he is not childless and the laws of yibum and chalitzah do not apply. It is equally clear that a deceased whose only surviving offspring is an under-developed prematurely born child is considered childless and his widow is subject to the laws of yibum and chalitzah.
What if a fully developed but prematurely born child survives the deceased? Is the widow subject to the laws of yibum and chalitzah? Biblically, in this situation, the deceased is considered not to have died childless and his wife is exempt from yibum and chalitzah. The rabbis however, apply a further condition to the exemption in this situation. They require that the fully-developed, prematurely born child actually survive for thirty days following the death of his father. If the fully-developed, prematurely born child did not survive thirty days, it is questionable whether the deceased died childless. Accordingly, the widow, though exempt from yibum, is rabbinically precluded from marrying another man unless and until she undergoes chalitzah. If, in this situation, the widow went ahead and married another man without first performing the chalitzah ceremony, the rabbis insist that the chalitzah ceremony be conducted with the brother-in-law after the marriage ceremony with the new husband.
The only situation in which the rabbis are prepared to waive this post-marriage chalitzah requirement is where the widow went ahead and married a kohen, priest. To insist on a post- marriage chalitzah ceremony in that situation would lead to the impossible situation of condoning the forbidden marriage of a kohen to a divorcee. This is because a woman who has received chalitzah is considered a divorcee. In this situation, the rabbis permit the widow to remain married to the kohen without a post-marriage chalitzah ceremony. The justification for this leniency is that chalitzah was not biblically required in this situation.
What if the deceased, though childless at the time of his death, is survived by a widow in the early stages of pregnancy who subsequently gives birth to the deceased’s child? Is the deceased considered to have died “childless” and is his widow subject to yibum or chalitzah? Here again, if the posthumous child is born full term, the deceased is not considered to have died childless and the widow is exempt from yibum and chalitzah. This is the case even if the child died a moment after birth. If, however, there is doubt as to whether the child was full term, and the child does not survive for thirty days following his father’s death, the widow, though exempt from yibum, must undergo chalitzah.
What if immediately following the death of her husband, the widow enters into a yibum marriage with her brother-in-law, unaware that she is in the early stages of pregnancy from her deceased husband? Subsequently, the widow gives birth to the fully developed full-term child of her deceased husband. In this situation, the widow is an ervah to her brother-in-law because the marriage between a man and his brother’s wife is prohibited under the sanction of karet and is ineffective unless the deceased died childless. In this case it transpires that the deceased did not die childless. There is no alternative in this unfortunate situation but to separate the widow and her brother in-law.
In practice, this situation is unlikely to arise because the rule is that the widow and the brother-in-law must wait a period of ninety days before entering into yibum or conducting chalitzah. The purpose of this three-month hiatus is to avoid the type of unfortunate situation just described. Indeed, the requirement for a widow to wait three months before remarrying exists in all situations, in order to avoid uncertainty as to whether the newborn was a child of the deceased husband or the new husband.
Being able to identify the father with certainty is not just a matter of pedigree. It can help prevent subsequent inadvertent forbidden unions. Thus, for example, the child, believing he is the offspring of his mother’s new husband, might enter into a marriage with the daughter of his mother’s first husband and unwittingly transgress the violation against marrying one’s paternal sister. So determined were the rabbis to avoid doubt as to the identity of the father that they enforced the hiatus period even in circumstances where confusion was unlikely to occur, such as where the first husband died after kiddushin but before nisuin without having consummated the marriage. Others, witnessing such a marriage and being unaware of the special circumstances of the case, might jump to the conclusion that all widows may skip the hiatus period.
It would appear that because of this very concern, even today, when a simple medical test can determine whether or not the widow is pregnant or a micro-satellite DNA test can determine paternity, the hiatus period still applies.