Is this article correct in saying Implantation can be completed as early as eight days or as late as 18 days after fertilization?
When Is a Woman Pregnant?
To be sure, not every act of intercourse results in a pregnancy. First, ovulation (i.e., the monthly release of a woman's egg) must occur. Then, the egg must be fertilized. Fertilization describes the process by which a single sperm gradually penetrates the layers of an egg to form a new cell ("zygote"). This usually occurs in the fallopian tubes and can take up to 24 hours.
There is only a short window during which an egg can be fertilized. If fertilization does not occur during that time, the egg dissolves and then hormonal changes trigger menstruation; however, if fertilization does occur, the zygote divides and differentiates into a "preembryo" while being carried down the fallopian tube toward the uterus.
Implantation of the preembryo in the uterine lining begins about five days after fertilization. Implantation can be completed as early as eight days or as late as 18 days after fertilization, but usually takes about 14 days. Between one-third and one-half of all fertilized eggs never fully implant. A pregnancy is considered to be established only after implantation is complete.
Source: American College of Obstetricans and Gynecologists.
To my knowledge yes & it also explains why I could NOT have gotten pregnant when they said I did with my one son. Even though I was off on u/s measurements for dates they stuck with my LMP based EDD...so I actually think he was a full week younger than they said & then he had soft markers at birth to show he could be earlier than they thought...like a bite down reflex when nursing & undescended testicles & not breathing at birth ( he did fine once they resuscitated him)...but those are all much more common issues in babies before 36 weeks & they kept insisting he was 37 weeks.