If a daughter is born first it is a good omen for sons/ a first-born daughter is a sign that sons will follow
When a first-born daughter is born, it serves as a sign for the birth of sons after her. Or: it is good for the sons who will be born after the daughter, as she can assist their mother in raising them.
(Regarding inheritance – a son is preferable for him; regarding wellbeing – his daughter is preferable to him... as Rav Chisda said: a daughter first is a good sign for sons – Bava Batra 61a)
Translation
Expression (Hebrew)
בַּת תְּחִלָּה- סִימָן יָפֶה לְבָנִים
Definition (Hebrew)
כְּשֶׁנּוֹלַדְתְּ בַּת בְּכִירָה הַדָּבָר מְהַוֶּה סִימָן לְלֵדַת בָּנִים אַחֲרֶיהָ. אוֹ: טוֹב לַבָּנִים שֶׁיִּוָּלְדוּ אַחֲרֵי הַבַּת שֶׁתּוּכַל לְסַיֵּעַ לְאִמָּם בְּגִדּוּלָם.
("לְעִנְיַן יְרֻשָּׁה- בֵּן עָדִיף לֵהּ, לְעִנְיַן הָרְוָחָה- בִּתּוֹ עֲדִיפָא לֵהּ...דְּאָמַר רַב חִסְדָּא: בַּת תְּחִלָּה סִימָן יָפֶה לְבָנִים"-בָּבָא בָּתְרָא קַמָּא ע"א)