Ibn Abi Najih narrates from Mujahid (may Allah have mercy on him) concerning the statement: "And it is not lawful for them to conceal what Allah has created in their wombs" [Surah al-Baqarah: 228], that it means: if they are pregnant, they deny the pregnancy, or if they are not pregnant, they declare a pregnancy.
Layth bin Abi Sulaym narrates it from Mujahid (may Allah have mercy on him) concerning both menstruation and pregnancy.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الرجعة / 15185