Answer :
If fertilization occurs Estrogen triggers the thickening of the endometrium.
Fertilization is a complex multistep molecular technique where relatively methylated and certain haploid gametes, spermatozoon and oocyte, are coming collectively forming a male and a woman pronucleus, respectively, and culminating in the fusion of the two pronuclei giving an upward pull to the formation of the zygote.
Fertilization happens when a sperm fuses with the woman's act during intercourse and in addition, forms an egg that receives implanted within the uterus of the woman. The sperm travels through the fallopian tube and penetrates the zona pellucida layer of the ovum (girl egg) and fuses with it which paperwork a zygote (fertilized egg).
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