Said between husband and wife
A short duʿā with a stated effect on the child.
لَوْ أَنَّ أَحَدَكُمْ إِذَا أَتَى أَهْلَهُ قَالَ بِسْمِ اللَّهِ اللَّهُمَّ جَنِّبْنَا الشَّيْطَانَ وَجَنِّبِ الشَّيْطَانَ مَا رَزَقْتَنَا. فَقُضِيَ بَيْنَهُمَا وَلَدٌ، لَمْ يَضُرَّهُ
Bismillāh, Allāhumma jannibna-sh-shayṭāna wa jannibi-sh-shayṭāna mā razaqtanā.
“In the name of Allah. O Allah, keep Satan away from us, and keep Satan away from what You provide us.”
The full narration
Narrated Ibn `Abbas:The Prophet (ﷺ) said, "If anyone of you on having sexual relations with his wife said (and he must say it before starting) 'In the name of Allah. O Allah! Protect us from Satan and also protect what you bestow upon us (i.e. the coming offspring) from Satan,' and if it is destined that they should have a child then, Satan will never be able to harm that offspring
Source
Ṣaḥīḥ al-Bukhārī · 141
- Agreed upon as authentic (al-Bukhārī / Muslim)