However the ratio may deviate significantly from this range for natural reasons such as early marriage and fertility, teenage mothers, average maternal age at birth, paternal age, age gap between father and mother, late births, ethnicity, social and economic stress, warfare, environmental and hormonal effects.
Namun, rasio tersebut dapat menyimpang secara signifikan dari kisaran ini dengan alasan alami seperti pernikahan dini dan kesuburan, ibu usia remaja, usia ibu rata-rata saat lahir, usia ayah, perbedaan usia antara ayah dan ibu, kelahiran akhir, etnisitas, stres sosial dan ekonomi, peperangan, efek lingkungan dan hormonal.