﴿ ٱللَّهُ يَعْلَمُ مَا تَحْمِلُ كُلُّ أُنثَىٰ وَمَا تَغِيضُ ٱلْأَرْحَامُ وَمَا تَزْدَادُ ۖ وَكُلُّ شَىْءٍ عِندَهُۥ بِمِقْدَارٍ ﴾

“God knows what any female bears [in her womb], and by how much the wombs may fall short [in gestation], and by how much they may increase [the average period]: for with Him everything is [created] in accordance with its scope and purpose.”

Please check ayah 13:9 for complete tafsir.