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Throughout pregnancy, the fetal-placental unit secretes protein and steroid hormones and eicosanoids that alter the function of every endocrine gland in the mother’s body. Both clinically and in the laboratory, pregnancy can mimic hyperthyroidism, Cushing disease, pituitary adenoma, diabetes mellitus, polycystic ovary syndrome, and more.
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The endocrine changes associated with pregnancy are adaptive, allowing the mother to nurture the developing fetus. Although maternal reserves are usually adequate, in cases of gestational diabetes or hypertensive disease of pregnancy, a woman may develop overt signs of disease as a direct result of pregnancy.
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Aside from creating a satisfactory nutritive environment for fetal development, the placenta serves as an endocrine, respiratory, alimentary, and excretory organ. Measurements of fetal-placental products in the maternal serum provide one means of assessing fetal well-being. This chapter will consider the changes in maternal endocrine function in pregnancy and during-parturition as well as fetal endocrine development. The chapter concludes with a discussion of some endocrine disorders complicating pregnancy.
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CONCEPTION AND IMPLANTATION
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In fertile women, ovulation occurs approximately 12 to 16 days after the onset of the previous menses. The ovum must be fertilized within 24 to 48 hours if conception is to result. For about 48 hours around ovulation, cervical mucus is copious, nonviscous, slightly alkaline, and forms a gel matrix that acts as a filter and conduit for sperm. Sperm begin appearing in the outer third of the fallopian tube (the ampulla) 5 to 10 minutes after coitus and-continue to migrate to this location from the cervix for about 24 to 48 hours. Of the 200 × 106 sperm that are deposited in the vaginal fornices, only approximately 200 reach the distal tube. Fertilization normally occurs in the ampulla.
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Implantation and hCG Production
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After fertilization and zygote transport into the endometrial cavity, blastocyst invasion of the uterus occurs during a specific window of implantation 8 to 10 days after ovulation. ...