I have read that the timings for intercourse should not be between sunset and till the redness of sky disappears. In the event of a child being born out of this act, how bad can it be? What will the effect be on the child, who was born as a result of the timings?

All these recommendations and instructions are just as a precautionary recommendations such as to avoid any mismanagement in your ebadat specially the wajib one like Salatul Maghrib. Also as it’s very clear this particular time ( close to sun set or sun rise) is very short and as for as privacy concern always there is a chances that there an obstacle can come so if a person is at his/her home then this can be possible any time but if a person is out of such environment and let’s say he/she is on trip and in hotel then they have to pay respect to their Salat timing. Therefore it’s not Haram at all and not even sin, it’s a extra ordinary precaution take by Islamic Shariya that also shows how accurate our religion is and how respectful towards our Modesty and Spirituality too. The only thing is give sadaqah (Charity) for safety of the child and rely on Allah (swt). But always try to be together with you spouse at least one hour of your meal ( I mean food you have taken) and do Wudhu before being together, always say Bismillahirrahmanirrahim and seek protection with Allah from the cursed Shaitan.