“Say (O Muhammad SAW): "Come, I will recite what your Lord has prohibited you from: Join not anything in worship with Him; be good and dutiful to your parents; kill not your children because of poverty - We provide sustenance for you and for them; come not near to Al-Fawâhish (shameful sins, illegal sexual intercourse,) whether committed openly or secretly, and kill not anyone whom Allâh has forbidden, except for a just cause (according to Islâmic law). This He has commanded you that you may understand.” (7:151)

In the tafseer of Imam Qurtubee he mentions the tafseer on the text (kill not your children) he says;

“Some of the fuqahaa have deduced from this verse the impermissibility of performing Azl (withdrawing the penis before emission of semen to avoid conception) because the sperm gives birth to lineage and withdrawing it is preventing that to happen. Thus it is similar to killing a child except that killing by itself is more severe in sin than Azl. This is why some of our scholars have understood Azl  being something detested, not prohibited which was also held by a group of companions due to the saying of the prophet of Allah narrated by Judama daughter of Wahb;

‘then they asked him (prophet of Allah) about azl and Allah’s Messenger (peace be upon him) replied, “that is the secret burying alive” [reported by Muslim]”

The reason behind mentioning Azl is because if azl itself is declared as ‘secret burying alive’ then how about killing a child for no valid reasons? Azl itself is the first step towards the birth of a child, let alone him being in the seventh week of progression. So, if scholars viewed azl being haram then using excuse of seventh week is absolutely invalid.

Another issue you mentioned is that he will fear being ridiculed by people. This is not as bad as killing a child due to fear of poverty and that has been made haram by Allah. So, what excuse on has for mere ‘laughter’ of people? This is utter ignorance and lack of accountability for one’s actions as Allah mentions;

‘Because of that We ordained for the Children of Israel that if anyone killed a person not in retaliation of murder, or (and) to spread mischief in the land - it would be as if he killed all mankind’ [5:32]

Thus, killing a soul without any Islamic reason is a grave sin and as we have been told in a Hadith that the first actions accounted by Allah will be related to blood (killing).

Another aspect is that the Prophet of Allah (peace be upon him) encouraged us to marry women who can bare a lot of children so that his nation will out number all the previous nations. This again is a blessing to have not the opposite.

Finally, if he cannot afford or for any other reasons to have another child then it is obligatory upon you both to use contraceptives and not become pregnant. This is because, anything which leads to haram itself is haram. So if by you becoming pregnant will lead to killing the child then your becoming pregnant is haram.