Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
darimi:962ʿUbaydullāh b. Mūsá > ʿUthmān b. al-Aswad > Saʾalt Mujāhid > Āmraʾatī Raʾat Dam > Urāhā Ḥāmil

[Machine] My wife saw blood and I saw her pregnant. He said, "That is the shedding of the womb. Allah knows what every female carries, what the wombs shed, and what they increase. And everything has its extent" [Surah Ar-Ra'd, verse 8]. So, whatever she shed, it increased similarly in her pregnancy.  

الدارمي:٩٦٢أَخْبَرَنَا عُبَيْدُ اللَّهِ بْنُ مُوسَى عَنْ عُثْمَانَ بْنِ الْأَسْوَدِ قَالَ سَأَلْتُ مُجَاهِدًا

عَنْ امْرَأَتِي رَأَتْ دَمًا وَأَنَا أُرَاهَا حَامِلًا؟ قَالَ ذَلِكَ غَيْضُ الْأَرْحَامِ {اللَّهُ يَعْلَمُ مَا تَحْمِلُ كُلُّ أُنْثَى وَمَا تَغِيضُ الْأَرْحَامُ وَمَا تَزْدَادُ} [الرعد 8] فَمَا غَاضَتْ مِنْ شَيْءٍ زَادَتْ مِثْلَهُ فِي الْحَمْلِ