He it is Who shapes you in the wombs as He pleases. Lâ ilâha illa Huwa (none has the right to be worshipped but He), the All-Mighty,
the All-Wise. [Qur'an 3:6]

Du'a (Supplication)
A good dua (supplication) to make when desiring a child:

The Noble Qur'an - Al-A'raf 7:189

It is He Who has created you from a single person (Adam), and (then) He has created from him his wife [Hawwa (Eve)], in order that he might enjoy the pleasure of living with her. When he had sexual relation with her, she became pregnant and she carried it about lightly. Then when it became heavy, they both invoked Allâh, their Lord (saying): "If You give us a Sâlih (good in every aspect) child, we shall indeed be among the grateful."

Dua for infertile couples:

The du'a of Zakariyya (Zakariah), 'alayhis-salaam, which he made in his old age while his wife was barren but Allah, swt, answered his call and gave him Yahyah (John), 'alayhis-salaam.

The Noble Qur'an Al-'Imran 3:38

"Rabbi hab li min ladunka dhurriyyatan tayyibatan innaka samee' al-du'aa' "

..."O my Lord! Grant me from You, a good offspring. You are indeed the All-Hearer of invocation."

Dua that can be made often during the woman's labor pains or any other times of distress and hardship:

Allaahumma laa sahla 'illa maa ja'altahu sahlan wa 'anta taja'lu-l-hazna 'idha shi 'ta sahlan. - "O Allah, there is nothing easy except what You make easy. You can make grief, if You wish, easy." [Recorded by ibn al-Sunee; According to al-Hilaali, this hadith is sahih. See al-Hilaali,
vol. 1, p. 345.]

All Babies are Born Muslim

Hadith - Sahih Bukhari 8.597 (See also 2.467), Narrated Abu Huraira

Allah's Apostle was asked about the offspring of the pagans. He said, "Allah knows what they would have done (were they to live)."

Narrated Abu Huraira: Allah's Apostle said, "No child is born but has the Islamic Faith, but its parents turn it into a Jew or a Christian.
It is as you help the animals give birth. Do you find among their offspring a mutilated one before you mutilate them yourself?" The people said,

" O Allah's Apostle! What do you think about those (of them) who die young?" The Prophet said, "Allah knows what they would have done
(were they to live)."

The Noble Qur'an Ar-Rum 30:30

So set you (O Muhammad SAW) your face towards the religion of pure Islâmic Monotheism Hanifa (worship none but Allâh Alone) Allâh's Fitrah (i.e. Allâh's Islâmic Monotheism), with which He has created mankind. No change let there be in Khalq­illâh (i.e. the Religion of Allâh Islâmic Monotheism), that is the straight religion, but most of men know not.