Revision as of 20:40, 7 November 2009

601

Demographic studies of fertility ¹ (621-.3) deal with certain phenomena connected with human reproduction ². The term natality ¹ is sometimes used instead of fertility. These studies are mainly concerned with births ³ and the birth rate (630-.1) of populations and with the factors affecting them. A birth is the act or process of delivering a child. A distinction used to be made between a live birth ⁴ resulting in the delivery (603-.4*) of a live-born child ⁵ and a stillbirth (410-.6), the delivery after about the sixth month of pregnancy of a foetus that died before or during delivery. The term effective fertility ⁶ has sometimes been used when late foetal deaths (410-.6), and in some cases the deaths of infants or children, are excluded from consideration. The term total fertility ⁷ has on occasions been used to refer to live births and late foetal deaths combined.

• 1. fertility n. — fertile adj.
• 2. reproduction n. — reproduce v. — reproductive adj.
• 3. It is becoming more and more common, to use the term birth to mean live births in view of the introduction of the term late foetal death for still births (410-.6*).

602

Conception ¹, the fertilization ² of the female ovum ³ by a male sperm ⁴ or spermatozoon ⁴ is the beginning of pregnancy ⁵ or gestation ⁵, which consists of the development of the product of conception ⁶ in. the form of an embryo ⁷ or foetus ⁷ (the American spelling is fetus ⁷). Although the distinction between an embryo and a foetus is not precisely defined, the term "embryo" is generally used for the earliest stages of foetal development. An early process in pregnancy is nidation ⁸, the implantation of the fertilized ovum in the wall of the uterus ⁹ or womb ⁹.

• 1. conception n. — conceive v.
• 2. fertilization n. — fertilize v. 5. pregnancy n. — pregnant adj.
• 7. embryo n. — embryonic adj. — embryology n., the science dealing with the development of embryos. foetus n. — foetal adj. 9. uterus n. — uterine adj.

603

A foetus is said to be non-viable ² during the first part of a pregnancy and viable ¹ thereafter. The change occurs when the foetus becomes capable of independent existence outside its mother, which is commonly considered to take place when the period of gestation ³ or duration of pregnancy ³ has lasted between 20 and 28 weeks. If the pregnancy has lasted longer than this, the expulsion of the foetus (alive or dead) takes place during confinement ⁴; an earlier expulsion is called an abortion ⁵ (cf. para. 604-). The period of about six weeks after delivery (during which the uterus usually regains its normal size and in which the probability of conception is low) is called the puerperium ⁶ (424-.3).

• 1. viable adj. — viability n.
• 4. The actual process of the expulsion of the foetus is called delivery or parturition, which is the termination of labour.
• 5. abortion n. — abort v.
• 6. puerperium n. — puerperal adj.

604

A spontaneous abortion ¹, an unintentional abortion ¹ or, in nonmedical terms a miscarriage ¹ is an abortion which is not purposely caused. An intentional abortion ² or induced abortion ² is one which is purposely caused. A therapeutic abortion ³ is one which is undertaken to safeguard the health of the mother. The laws of certain countries permit legal abortions ⁴ for health or other reasons. Abortions which are induced contrary to law are called illegal abortions ⁵ or criminal abortions ⁵.

• 1. miscarriage n. — miscarry v.

605

Confinements (603-.4) and deliveries (603-.4*) are said to occur at term ¹ when the pregnancy has lasted for the normal period of about nine months. If pregnancy ends before the normal period (but after six months) there is a premature delivery ² or premature confinement ² or premature birth ² and the product of conception is called a premature baby ⁴. Births which are not premature are called births at term ³ or full-term births ³. The word prematurity ⁵ is sometimes used to refer to phenomena connected with premature delivery. A classification of births by stage of development that does not depend upon an estimate of the period of gestation is used in many countries. In this classification a live-born infant with a birth weight ⁶ of 5,5 lb. (2,500 grammes) or less is said to be immature ⁷.

606

Almost confinements there is a single birth ¹ or single delivery ¹, but at some there are plural births ², multiple births ² or multiple deliveries ². Two children born during the same confinement are called twins ³ and we may distinguish between monozygotic twins ⁴, uniovular twins ⁴ or identical twins ⁴ on one hand, and dizygotic twins ⁵, biovular twins ⁵, fraternal twins ⁵ or non-identical twins ⁵ on the other. Monozygotic multiple births occur when one ovum splits after fertilization; the resulting children must always be of the same sex. Dizygotic multiple births are due to the simultaneous fertilization of two or more ova and the resulting children may be of different sexes.

• 1. Single births result in one child only, who in medical literature is sometimes called a singleton.
• 2. The number of infants born in each delivery has been called litter size by some biometricians but in general, this term is reserved tor animals.
  In British official terminology the term maternity is used to denote a confinement resulting in the birth of one or more children; the number of births per maternity may be computed.
• 3. Where a multiple birth results in three children, these are called triplets, four are called quadruplets and five quintuplets. The terms "twins", "triplets", etc. may be used in different ways. Generally they are used in accordance with the total number of deliveries during a confinement, especially if at least one baby is born alive, e. g. one of a pair of twins may be alive when delivery is complete and the other dead. Occasionally, however, multiple births are classified only in accordance with the number of children born alive.

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