Maternity Nursing
360 NURSING BULLETS: Maternity and Newborn Nursing Reviewer 1.BASIC MATERNITY CONCEPTS The male sperm contributes an X or a Y chromosome; the female ovum contributes an X chromosome. Fertilization produces a total of 46 chromosomes, including an XY combination (male) or an XX combination (female). Organogenesis occurs during the first trimester of pregnancy, specifically, days 14 to 56 of gestation. Implantation in the uterus occurs 6 to 10 days after ovum fertilization. The chorion is the outermost extraembryonic membrane that gives rise to the placenta. The corpus luteum secretes large quantities of progesterone. From the 8th week of gestation through delivery, the developing cells are known as a fetus. The union of a male and a female gamete produces a zygote, which divides into the fertilized ovum. Spermatozoa (or their fragments) remain in the vagina for 72 hours after sexual intercourse. If the ovum is fertilized by a spermatozoon carrying a Y chromosome, a male zygote is formed.
