MATERNAL PHYSIOLOGY IN PREGNANCY

MATERNAL PHYSIOLOGY IN PREGNANCY

Ques. 1     Describe the Maternal Physiology in Pregnancy?

Ans.          Duration of Pregnancy – The average duration of human pregnancy counting from the first day of the last menstrual period is about 280 days or 10 lunar months or 40 weeks. Ovulation delivery interval is 267 days (as ovulation occurs on 13th or 14th day in 28 days cycle). Expected date of delivery (EDD) is calculated by counting back 3 months and adding 7 days or by counting forward 9 months and 7 days. This rule is know as “Nagele’s Rule”. Pregnancy prolonged beyond 42 weeks is known as post term or prolonged pregnancy.

One third of post term pregnancies are also associated with placental insufficiency and they are called post-maturity.

  1. OVARIES TUBES – The corpus luteum of pregnancy increases. Ovulation ceases. The atretic follicles show lutein like cells in theca folliculi. Decidua like changes are seen on surface of the ovary and tube as velvety patches. Ovarian blood vessels have increased enormously.
  2. BREASTS – After a few months the nipple are larger hypertrophied and erectile, and yellowish thin fluid of colostrums may be expressed. The areola becomes larger pigmented and darker. Sebaceous glands are hypertrophied and from glands of Montgomery. Stimulation and growth of the gland is hormonal. Initially, the women complains of a sense of tenseness and tingling in breasts. After the second month breasts are nodular, and bluish veins appear beneath skin.
  3. UTERUS – There is an increase in fibrous tissue and elastic tissue – lymphatic, blood vessles and the nerve plexus are hypertrophied. During the first 3 months of pregnancy the growth of the uterus is due to the action of oestrogen and progesterone. From the 3rd month onwards, uterus enlarges by distension which is mainly mechanical due to expanding products of conception. The most obvious maternal change in pregnancy is enormous increase in size of uterus. The small almost solid 6.5 cm. long uterus weighting 30 gm. Is converted into thin walled muscular sac 30 cm. long weighing 1000 gm. The enlargement of the uterus in early months of pregnancy is principally due to hypertrophy and to a certain extent hyperplasia of muscle fibres. The fully developed muscle fibres are 5 times wider and 10 times longer than those in non-pregnant uterus.
  4. VAGINA – Preparation for distension takes place in the form of hypertrophy of the musculature. Copious vaginal secretions are acidic due to break down of rich glycogen in vaginal epithelium by lactobacillus. Increased vascularity is a marked change in the vagina. This result in violet coloration and copious secretion.
  5. CERVIX – The glands of the endocervix undergo marked proliferation and at term they occupy half of bulk of the cervix and form physiological erosion of the cervix. One of the first (changes) physical signs noticed after pregnancy is pronounced softening of cervix. It is due to increased vascularity, oedema of the cervix, and hyperplasia of cervical glands.
  6. SKIN – Brownish patches of varying size appear over face giving rise to chloasma or masked appearance. All these changes are due to elevated levels of melanocyte stimulating hormone. Vascular spiders are seen over body. Reddish slightly depressed streaks or striae are seen on the skin of the abdomen and thighs. Nipples, areola are pigmented. Abdominal skin in midline is pigmented forming linea nigra.
  7. WEIGHT GAIN – Average total weight gain is about 11 kg., half of it in the last trimester, a similar amount in the second trimester and about 1 kg. in the first trimester. Rate of weight gain in the last trimester is about half kilogram per week. A few days before delivery there is a slight decrease in weight. Weight gain in pregnancy is due to the weight of foetus, uterus, placentra and amniotic fluid and in part due to metabolic alterations.
  8. LACTATION – Lactation comprises two function of the mammary gland, milk secretion and milk removal. Lactogenesis (initiation of milk) begins with parturition and progressively increases throughout puerperium reaching the maximum during the first and second weeks of puerperium. At this period the milk production varies from 800 to 1800 ml. per day. Length of human lactation varies from 6 to 12 months. During the first 6 months the infant is completely dependent on milk.
  9. NERVOUS SYSTEM –There is a craving for abonormal articles of diet and this known as pica. Also may be a change in disposition and in patients with psychotic disturbance emotional equilibrium is disturbed. Generally mild mental disturbances are common in pregnancy.

Ques. 2     What is Placenta ? Describe its development & functions.

Ans.          This is developed during pregnancy being primarily a chorionic structure and lies implanted on the uterin wall; it is connected with foetus through the umbilical cord; it maintains pregnancy and carries the vital foetal functions.

It is a wonderful organ development as a part of conceptus, is unique for its multiplicity of function inspite of simplicity in structure. It brings enormous changes in mother, mainly through its diverse hormones, to adapt the mother to the foetal needs. It grows along with foetus to maintain adequate channels of oxygen and nutrition, and protects foetus from noxious agents. A well developed healthy placenta ensures to a large extent a healthy foetus.

Ques. 3     What are the functions of placenta?

Ans.          The placenta serves the following purposes –

  1. Foetal excretory system – This removes waste metabolic substances from the foetus.
  2. Foetal barrier action due to placental membrane – This prevents any substance of large molecular size to pass from mother to the foetus, but sedatives and pain relieving drugs, hormones, volatile anaesthetic, antibiotics or chemotherapeutic agents, viruses particularly small pox, poliomyelitis, bacteria and parasites, antitoxins and antibodies cross placental membrane to reach foetus.
  3. Endocrine functions – Placenta acts as an additional endocrine gland during pregnancy.
  4. Enzyme function – various enzymes have been demonstrated in the placenta.
  5. Foetal respiratory organ – This supplies oxygen to and removes carbon dioxide from the foetus by a process of simple diffusion.
  6. Foetal alimentary organ- Water, glucose, amino acids, lipids, iron, calcium, sodium, vitamins are transferred from maternal circulation to the foetal circulation for foetal nutrition.

Ques. 4     What are the functions of placenta for the growing child in the mother’s womb?

Ans.          Placenta thus (i) maintains pregnancy and (ii) causes maternal changes for purpose of reproduction. Placenta is considered important component of the “foeto-placental unit”. (iii) serves vital foetal functions,

Development – The growing embryo in compact layer of the deciduas throws out the chorionic buds on all sides. Those towards deciduas capsularis, the chorion leave atrophy mainly due to lack of nutrition. Those in contact & attached to deciduas basalis, chorion frondosum proliferate, multiply & form the placenta. The formation of placenta occurs during 6th to 12th weeks of pregnancy. By 4th months, placenta has attained its definite form; thereafter it continues to grow throughout pregnancy.

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