Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 7 · Samskara Muhurtas
संस्कारमुहूर्ताः
भद्रा च संक्रमो निद्रा रात्रिश्चंद्रार्कयोर्ग्रहः ।कुलटा पापभोगेषु निंद्यर्क्षे निंद्यवासरे ॥ ३१६ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 316.
Bad times are Bhadra (bad half of a moon day) and a sankranti (the Sun's entry into a sign). So are sleep, night and an eclipse of the Moon or Sun. She may stray if the period comes in stars held by bad planets. So too in a blamed star or on a blamed weekday.
Simple meaning: A first period at these bad times may lead to a woman who goes astray.
आद्या निशश्चतस्रस्तु त्याज्या ह्यपि समाः परैः ।
Skip the first four nights after the period. Prefer the Moon in an odd sign and male planets looking at the lagna.
उपवीती युग्मतिथावनग्नः कामयेत्स्त्रियम् ।
A man who wants a son should keep to even moon days and avoid four stars.
प्रसिद्धे प्रथमे गर्भे तृतीये वा द्वितीयके ।
The rite for a son is done in the 2nd or 3rd month of the first pregnancy.