All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Muhammad and upon all of his family and companions.

First: Fulfilling a vow isn’t an obligation save it was allocated to perform an act of devotion or obedience, on the other hand, if the vow was made for performing a permissible act, then fulfilling it isn’t an obligation, for Al-Imam Ashrbini (May Allah have mercy on his soul) said (What means):”If a person made a vow to fulfill a permissible act .i.e. sleeping and eating or vowed to stop eating desert, then he isn’t obliged to fulfilled it in both cases, since Abu Dawood narrated, the Prophet (PBUH) said (What means): “There is no vow except in an act which seeks the pleasure of Allah, the Exalted. In addition, Ibn 'Abbas (May Allah be pleased with them) reported: While the Prophet (PBUH) was delivering Khutbah (religious talk), he noticed a man who was standing, so he asked about him and was told that he was Abu Israel who had taken a vow to remain standing and not sit, or go into the shade, or speak while observing fasting. Thereupon Messenger of Allah (PBUH) said: "Tell him to speak, to go into the shade, to sit and to complete his fast". [Related by Al-Bukhary]. [Mughni Al-Muhtaj vol.6 pp.235].

Second: In case the aforementioned vow occurred and you (Questioner) didn’t fulfill it, then you aren’t obliged to fulfill it at your wife’s next pregnancy, because the period of the vow has ended. Furthermore, according to our doctrine, the Shafiee’s school of thought, whoever made a vow to do a permissible act but didn’t do so, isn’t obliged to offer oath expiation because it isn’t considered a vow. Besides, in order to be on the safe side, you should feed 10 poor Muslims to free yourself from the liability. In conclusion, we urge you to name your son after the Prophet Muhammad (PBUH) name since Al-Imam Malik (May Allah have mercy on his soul) said: ”I heard the people of Al-Madina saying: ”Every family named their boy Muhammad, will have the best provisions.” And Allah Knows Best.