Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 2 · Signs, Planets, Birth
जातकम् १
युग्मभांशस्थितैस्तैस्तु वक्रेंदुभृगुभिस्तथा ।यामस्थानगतैर्वाच्यं स्त्रियो जन्म मनीषिभिः ॥ ५२ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 55, verse 52.
The same planets may be in even signs and even navamsha (one-ninth part of a sign). Or Mars, the Moon and Venus may be in even places. Then the wise say a girl is born.
Simple meaning: A girl is born when those planets are in even signs, or Mars, Moon and Venus are in even places.
द्व्यंगस्था बुधसंदृष्टाः स्वपक्षेय मलंकराः ।
Planets in dual signs seen by Mercury can give twins. Saturn in an odd house away from the lagna gives a boy.
मिथो रवींदूर्ज्ञार्की वा पश्यतः समगं रविः ।
These sights and odd-even placements are conditions; the next verse gives the result, a neuter birth.
कुजेक्षितेपुमांशेदुहिता क्लीब जन्मदा ।
Some placements seen by Mars give a neuter birth. Venus and Moon in even signs begin a twin rule.