Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) said: The Jews used to say that when a man has intercourse with his wife while she lies face down, the child is cross-eyed. So Allah Almighty revealed this verse: "Your wives are a tilth for you, so come to your tilth however you wish." [Surah al-Baqarah: 223] "If you wish, (do it) with her lying face down, or not, but only in the one designated place."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14104