In order to answer a question of this sort, one must enter the murky waters of Jewish customs, known as minhagim. This is by no means an easy area to deal with, since a good number of minhagim or Jewish traditions are local or even familial.
The very question implies a clear cut p’sak halakhah (juridical decision) across the board that forbids baby showers prior to birth or any gifts to a mother-to-be, however, this is far from clear. True, one can find numerous rabbis that will be quite adamant that any such gift is absolutely verboten.
Minhagim can take on the character of halakhah and once ingrained in the Jewish psyche it is next to impossible to shake. There is a concept found in the commentaries on the Talmud that declares, “minhag avoteinu Torah hi “(the custom of our ancestors is Torah).
This can be true as well in the area known in Hebrew as e-mu-not te-fay-lot (minor beliefs, i.e. superstitions). In fact, an emunah tefaylah can be so powerful that it takes over, becoming stronger in the minds of individuals than other unambiguous religious observances.
It may well be that the giving of a baby shower or mentioning the future name of a yet to be born baby was seen as to give an evil spirit (shaid or ruah ra’ah) an opportunity to bring about an unforeseen mishap, causing a disastrous termination of the birth. Another term used is ‘ayin hara’ (evil eye).
In past generations, stillbirths and fetal demise were more common than in our own day. There was less access to competent medical care and one needed to have everything going for this birth, including Torah, mitzvot and prayer. One could ill afford to tempt fate by breaking a strong superstition, especially when the minhag or tradition is presented as halakhah and goes unquestioned.
Still infertility and fetal demise is to be found in our day and each case brings untold pain in its wake. Baby showers and gifts can only inflict additional pain when the baby fails to be born. Many see that it is far better to leave everything in the hands of G-d and not test fate.
It is helpful to look into the phenomenon of superstition in Jewish tradition, nonetheless. Such matters can obtain in all areas of religious tradition. Take for instance, the practice in Ashkenazic communities on Yom Kippur and other holy days where Yizkor prayers of remembrance (Heb. hazkarat neshamot) are recited.
A prevalent custom is for congregants with living parents to exit the service at the point that Yizkor is recited. In many Orthodox congregations, today, rabbis plead with their congregants to stay in the service; nonetheless, there is often a mass exodus out the door, even though prayers for martyrs and Holocaust victims are included in the service, many leave.
The Kitzur Shukhan Arukh (Code of Jewish Law) states, “Our custom is that one who has a living father or mother, leaves the synagogue at the time of hazkarat neshamot (Yizkor), also, the custom is that during the first year of the death of the father or the mother one also leaves the synagogue.” (Order of Laws of Yom Ha-Kippurim Sec. 132:21)
Customs abound that seem to be rooted in superstition. There is a great deal of fear surrounding the nighttime and retiring to bed. Numerous prayers of reassurance are to be found in most siddurim (prayer books). Some prayer books contain very elaborate rituals for sleep time, occupying several pages.
The basic prayer while going to sleep is, of course, the declaration of keriat Shema (the first paragraph of Shema, Deuteronomy 6). Along with this, we can find much more, including a practice as recorded in the above-mentioned Kitzur Shulkan Arukh.
“Before one retires to bed he should walk to the mezuzah (doorpost parchment), placing his fingers upon it, he should recite, ‘G-d is my guardian…’ and afterward he should repeat seven times, ‘In all Your ways…’ and then [recite] the blessing of ‘G-d who causes sleep upon my eyelids’. He must not eat, drink or speak until he sleeps.” (Order of the Evening, Sec. 71:4)
There is another well-rooted custom known as Shalom Zakhar (welcoming the male), commonly pronounced in some communities Sholom Zokhor. On the Shabbat evening before the covenant of circumcision (b’rit milah) of a male child on the eighth day, a gathering takes place at the home of the newborn wherein symbolic foods are eaten and passages of religious writings are recited, especially coming from the Kabbalah (Jewish mysticism).
This is to protect the child from any possible harm prior to the circumcision. One cannot be too cautious.
Merely knowing the possible reasons rooted in Jewish superstitions for these and many other practices, including baby showers and gift giving prior to birth, will most likely do little to change our relationship to what has become common Jewish practice.
Every culture has its own culturally driven taboos and rituals. The Jews are entitled as any other people to have and respect their own.