The Embryo pp 209-226 | Cite as

The Endocrinology of the Fetoplacental Unit in the Second Trimester of Pregnancy

  • T. Chard
  • J. G. Grudzinskas

Abstract

The endocrinology of the human fetus and placenta presents a number of unique features when compared with the endocrinology of the normal adult. It is also a subject of great complexity, but certain generalizations are possible:
  1. 1.

    All glands and hormones characteristic of the adult are present in the fetus by the end of the first trimester. Control mechanisms (for example, pituitary-gonadal feedback) develop towards the end of the second trimester.

     
  2. 2.

    Fetal enodcrine systems are largely autonomous with respect to those in the mother so that the fetus has control over its own endocrine milieu from an early stage of pregnancy. Thus, normal children may be born to hypothyroid mothers. However, the fetus can respond to changes in maternal endocrine balance and the end-result of such a response may be pathological — for example, the excessive fetal growth associated with some cases of diabetes in the mother.

     
  3. 3.

    As a broad rule, protein and peptide hormones do not cross the placenta in significant quantities in either direction, while steroid hormones cross quite freely.

     
  4. 4.

    The fetal endocrine system has a number of unique “one-off” functions which are not repeated at any other stage of life. Examples include the differentiation of gonads and genitalia, and the initiation of parturition.

     
  5. 5.

    Throughout pregnancy the placenta secretes large quantities of both proteins and steroid hormones (Table 14.1). From the end of the first trimester onwards, the function of these placental hormones is doubtful or non-existent.

     

Keywords

Estrogen Corticosteroid Cortisol Prostaglandin Glucocorticoid 

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© Springer-Verlag London Limited 1991

Authors and Affiliations

  • T. Chard
  • J. G. Grudzinskas

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