Why is the waiting period (iddah) for a deceased woman four months and ten days, while her waiting period ends if she gives birth immediately after her husband's death?

The wisdom behind the 'iddah (waiting period) of a widow is not solely to honor the husband; rather, there are other reasons mentioned by Ibn al-Qayyim. Among them is that the four months and ten days is the period during which the presence or absence of pregnancy becomes known. During this time, the fetus is a nutfah (sperm-drop) for forty days, then an 'alaqah (clot) for forty days, then a mudghah (lump of flesh) for forty days. This totals four months, after which the soul is breathed into it in the fourth stage. The ten days were added to show its life through movement, if there is a pregnancy. Al-Tabari narrated from Qatadah, who quoted Sa'id ibn al-Musayyib as saying: "What about the ten days?" He replied: "It is when the soul is breathed in." This wisdom aligns with the 'iddah ending upon delivery for the purpose of ensuring the purity of the womb. It is obligatory to submit to Allah's decree.