Witnesses properly rejoice and give each other gifts when the occasion is appropriated and it does not include unscriptural, pagan customs or practices that go contrary to Christian principles. (While there may in some areas be false religious customs associated with the celebrations of the birth of a baby, Christians do not include these customs in their rejoicing.)
Just looking at the birth of Christ would tell you that it was OK for God’s people to rejoice and gather together in celebration of a birth (Luke 2). God Himself rejoiced when Jesus was born. The angels rejoiced and gathered together and even invited the shepherds to gather! Granted, this celebration was for more than just a child’s birth, but there are many other scriptural examples of parents and friends rejoicing at the birth of a child.
On the other hand, you will also note that there is not even one example in the Bible of God’s faithful servants who commemorated the “birthday” of anyone. Jehovah’s people celebrated other anniversaries but they did not memorialize the date of birth (Jn 10:22, 23).
Further, even the idea of elevating an individual just because he was born is contrary to Christian principles. Birthdays are rooted in selfish pride and all about “Me.” Jesus gave us a guiding principle of humility not self-exaltation (Mat. 23:12; Gal. 5:26).
While we might be able to avoid the egotistical aspect, a bigger principle is involved. It is a matter of practicing unadulterated True Worship as taught in the Scriptures. Celebrating birthdays was unheard of by God’s people for hundreds of years after Christ and only came about with the corruption of True Christianity by false teachers.
Just the slightest research would tell you that celebrating birthdays is not a practice for True Christianity:
"The celebration of birthdays has been borrowed from the practices of other nations, as no mention is made of this custom among Jews either in The Bible, Talmud, or writings of the later Sages. In fact, it was an ancient Egyptian custom."--Customs and Traditions of Israel
The World Book Encyclopedia states: “The early Christians did not celebrate [Jesus’] birth because they considered the celebration of anyone’s birth to be a pagan custom.”
“Early Christians did not celebrate the birth of Christ. Birthdays in themselves were associated with pagan practices; the Gospels say nothing about the actual date of Christ’s birth.”--The Making of the Modern Christmas, by Golby and Purdue
"The later Hebrews looked on the celebration of birthdays as a part of idolatrous worship, a view which would be abundantly confirmed by what they saw of the common observances associated with these days."--*The Imperial Bible-Dictionary
One periodical stated: "The various customs with which people today celebrate their birthdays have a long history. Their origins lie in the realm of magic and religion. The customs of offering congratulations, presenting gifts and celebrating - complete with lighted candles - in ancient times were meant to protect the birthday celebrant from the demons and to ensure his security for the coming year. . . . Down to the fourth century Christianity rejected the birthday celebration as a pagan custom."
"Birthday greetings and wishes for happiness are an intrinsic part of this holiday. . . . originally the idea was rooted in magic. The working of spells for good and evil is the chief usage of witchcraft. One is especially susceptible to such spells on his birthday, as one's personal spirits are about at the time. . . . Birthday greetings have power for good or ill because one is closer to the spirit world on this day....The keeping of birthday records was important in ancient times principally because a birth date was essential for the casting of a horoscope."--The Lore of Birthdays
Celebrating birthdays was adopted from superstition and false religion which corrupted true Christianity.
The Israelites also adopted a religious practice which they renamed as "a festival to Jehovah" and "sat down to eat and drink and to have a good time" (Ex.32:1-35). Even though the Israelites used this festival to worship the True God, God still viewed this as idolatry, and that is also true of customs today that are clearly derived from false religious practices (Lev.18:3; Deut.12:30, 31; Jer. 10:2; 1Cor.10:6- 11). True Christians will listen to what God's thinking and avoid any association with idolatrous, corruptive non-Christian practices in their pure worship of the True God.
We are told: "Therefore get out from among them, and separate yourselves, says Jehovah, and quit touching the unclean thing; and I will take you in."-2 Cor. 6:14-18, Isa.52:11; Gal.5:9)
The only birthday celebrations of Biblical record are of pagans and linked to instances of cruelty. Hence, the Scriptures clearly place birthday celebrations in a negative light, a fact that sincere Christians do not disregard.
Consequently, while it is entirely a private matter if Christians choose to take note of baby showers or wedding anniversaries, there are good reasons why mature Christians abstain from celebrating birthdays.
**As a side note, pointing to the “wise men” as a reason to celebrate birthdays requires us to be ignorant of the Scriptures. First, they were not “wise men” but “magi” or astrologers and thus were not worshipers of the True God. Second, they were not even around at the time of Christ’s birth and so their gifts were not for his “birthday.” Notice that he was in a “house” and is described as a “young child,” not as a newborn baby.—Mat 2:1-10.
SOURCE: This is an answer provided by BAR_ANERGES to a question at Yahoo Answers.
Additional Comments to BAR_ANERGES answer:
1.) Distinction between Baby Showers and Birthdays. Baby showers today are a way to celebrate the pending or recent birth of a child by presenting gifts to the parents at a party. It is not a celebration of the specific birthdate of the child by presenting gifts to the child itself.
2.) Baby showers are not of pagan origin. The origin of baby showers is unknown: Baby Shower History (Ezine @rticles)
Although something like baby showers were practiced by people in the past, it appears modern baby showers are not connected to ancient baby showers in any way.
So "baby showers" as we know them today are a modern invention, and cannot be of pagan origin. Besides, (and most importantly) the Bible describes God’s people as having rejoiced and “celebrated” the birth of their children whereas there are good reasons why mature Christians abstain from celebrating birthdays.
3.) The holding of baby showers is nowhere promoted in literature produced by the Watchtower Bible and Tract Society. It is not an official practice of Jehovah's Witnesses; it is at best a personal choice. We don't have to "stop" doing something we do not officially promote in the first place. "Jehovah's Witnesses" do not have baby showers, individuals do, if they so wish. And even then the emphasis is on helping the parents, not celebrating a birthday.
For more concerning Birthdays, see:
Jehovah's Witnesses and Birthdays - Why Don't They Celebrate? (Defend Jehovah's Witnesses)
What Are Some Customs That Displease God? (w05 1/1 pp. 27-30; Watchtower Online Library)