are called the nutfa al-amshāj (the mixed germinal drop). It adheres to the uterine wall; the womb closes in around it firmly and shuts the gateway so that no other sperm can enter.

The embryo is then nourished through the umbilical cord, which is attached to the infant’s navel at one end, while the other end is anchored in the placenta, from which it draws refined sustenance taken from its mother.

Dr. al-Bār states: “Once a sperm cell fertilises its ovum, the ovum erects around itself a sealed wall that no other sperm can penetrate—neither from this act of intercourse nor from any later act, neither from this man nor from any other. Should two sperm cells enter the same ovum, the result would be the death of the zygote and its expulsion from the womb.

“As for twins, they are of two kinds:

1. Identical twins arise from a single sperm cell and two ova; after fertilisation the zygote divides and separates, producing two embryos that are entirely alike.
2. Fraternal twins are non-identical: two sperm cells fertilise two separate ova, each sperm fertilising one ovum, so they resemble ordinary siblings born of the same parents.” End quote.

I say: The claim that the uterus closes completely after fertilisation is incorrect. The cervical opening remains as it is, and semen can still reach the uterus and even the Fallopian tube… Perhaps this phenomenon—Allah knows best—is like a person irrigating another man’s field.