hello, I
am in my seventh month of my second pregnancy. i allready
have a girl, and now my husband doesn't want to know the
sex of the baby. For him it doesn't seem to be important,
and he didn't want to ask the doctor about the sex. He wants
to wait so that it will be a surprise; but i really want
a boy. At this time, can i still pray for the sex? I have
faith that G-d, is hearing my prays, and i think, meanwhile
this baby is inside of me miracles could happen. What do
you think? thank you, and i will wait for your answer.

Shalom,
First of all, let me wish you all the best for a healthy
and easy birth, and may you and your husband merit to establish
a good and faithful home.
In connection
with your question- may you pray during pregnancy that your
child be a boy. See the Mishna in tractate Brachot (54a)
"Someone who cries out [in prayer] about past matters,
behold that is a false prayer [tefillat shav]. If one's
wife is pregnant, and one prayed "May it be Your will
that my wife gives birth to a boy" behold that is a
false prayer."
The Gemara
(ibid, 60a) asks a question on this law- behold we learn
that Leah prayed that her child should be a girl and not
a boy (in order that Rachel also merit to give birth to
a large number of the male descendants of Jacob, who would
latter become the heads of the twelve tribes. Her prayer
was answered and Dina was turned into a girl in the womb.
The gemara gives two explanations, one- that we can not
learn from a miracle, and secondly- that within the first
forty days of conception one is allowed to pray that the
sex of the child be changed either to a boy or girl [this
would apply even if one had an early ultrasound, and knew
the sex of the child]. The Shulcan Aruch (Orach Chaim 230, 1) rules that in the
first forty das after conception, one may pray for the sex
of the child, but after this it is a false prayer, and as
such is forbidden. [Incidently, I have been told that recently
it has been proved scientifically that the sex chromosomes
can change in the first stages of pregnancy- reported in
the Science Section of the New York Times.]
One may,
however, pray that the child be healthy, and upright, etc.
during all the pregnancy.
May you
be blessed with a healthy and holy child- boy or girl according
to Hashem's wishes.
Rabbi Da'vid
Sperling