"God knows what every female bears" of a male or a female, "and what the wombs lose and what they add." Al-Hasan's interpretation: He said: 'Ghaydudah' (loss) is giving birth in less than nine months. "And what they add" means: giving birth in more than nine months. 'Ghaydudah' is deficiency.
"And everything with Him is by a measure," meaning: by a quantity.
﴿اللَّهُ يَعْلَمُ مَا تَحْمِلُ كُلُّ أُنْثَى﴾ مِنْ ذَكَرٍ أَوْ أُنْثَى ﴿وَمَا تغيض الْأَرْحَام وَمَا تزداد﴾ تَفْسِيرُ الْحَسَنِ: قَالَ: الْغَيْضُوضَةُ أَنْ تَلِدَ لأَقَلِ مِنْ تِسْعَةِ أَشْهُرٍ ﴿وَمَا تزداد﴾ يَعْنِي: أَنْ تَلِدَ لأَكْثَرِ مِنْ تِسْعَةِ أَشْهُرٍ، الْغَيْضُوضَةُ: النُّقْصَانُ.
﴿وَكُلُّ شيءٍ عِنْده بِمِقْدَار﴾ أَي: بِقدر
