Qatāda said: “‘What the wombs lose’ refers to miscarriage, and ‘what they gain’ refers to anything beyond nine months.”

Sa‘īd ibn Jubayr said: “When a woman sees blood during pregnancy, this is a loss to the child: it diminishes the child’s nourishment and lengthens the pregnancy.”

“Lose” and “gain” are two transitive verbs whose object is omitted; it is the pronoun referring back to the relative pronoun “what.” Loss means diminution, as in 11:44: “And the water subsided.” Its opposite is increase.

The precise meaning of the verse is that He knows the duration of pregnancy and whatever increase or decrease occurs during it. He alone knows this, not you, just as He knows what every female bears: whether it is male or female. This is one of the matters of the unseen known only to Allah Most High, as reported from the Prophet, peace and blessings be upon him, in the two Sahīh collections:

“The keys to the unseen are five; none knows them but Allah. None knows what is in the wombs but Allah, and no soul knows in what land it will die; only Allah knows.”

He alone, glorified be He, knows what is in the womb, how long it remains there, and what increases or diminishes in its body.

The other interpretations concern consequences and implications of this explanation, such as miscarriage and reaching full term, and the appearance and cessation of bleeding. The point is to mention how long the unborn child remains in the womb and the related increase or decrease.

[Surah Thunder (13): Verse 17]

“He sends down water from the sky, and valleys flow according to their capacity. The torrent carries swelling foam, and a similar scum comes from what people heat in the fire to make ornaments or utensils. Thus Allah illustrates truth and falsehood. As for the foam, it is cast away, while what benefits people remains on the earth. Thus Allah sets forth parables.” (17)

Allah likened the revelation He sent down to give life to hearts, hearing, and sight to the water that