It was narrated from Anas that: Umm Sulaim asked the Messenger of Allah (ﷺ) about a woman who sees in her dream something like that which a man sees. The Messenger of Allah (ﷺ) said: "If she sees that and has a discharge, then let her perform a bath." Umm Salamah said: "O Messenger of Allah, does that really happen?" He said: "Yes, the water of the man is thick and white and the water of a woman is thin and yellow. Whichever of them comes first or predominates, the child will resemble (that parent)."
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا ابْنُ أَبِي عَدِيٍّ، وَعَبْدُ الأَعْلَى، عَنْ سَعِيدِ بْنِ أَبِي عَرُوبَةَ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، أَنَّ أُمَّ سُلَيْمٍ، سَأَلَتْ رَسُولَ اللَّهِ ـ صلى الله عليه وسلم ـ عَنِ الْمَرْأَةِ تَرَى فِي مَنَامِهَا مَا يَرَى الرَّجُلُ فَقَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ " إِذَا رَأَتْ ذَلِكَ فَأَنْزَلَتْ فَعَلَيْهَا الْغُسْلُ " . فَقَالَتْ أُمُّ سَلَمَةَ يَا رَسُولَ اللَّهِ أَيَكُونُ هَذَا قَالَ " نَعَمْ مَاءُ الرَّجُلِ غَلِيظٌ أَبْيَضُ وَمَاءُ الْمَرْأَةِ رَقِيقٌ أَصْفَرُ فَأَيُّهُمَا سَبَقَ أَوْ عَلاَ أَشْبَهَهُ الْوَلَدُ " .
sunnah.com