The physiology of birth, puerperium and lactation

Objectives Describe physiology of initiation of labor Define normal and abnormal labor Describe normal puerperium 11/21/2018

Parturition Normal Pregnancy Parturition Uterine quiescence Fetus Mother Placenta Membranes Normal Pregnancy Uterine quiescence Immature fetus Closed cervix Parturition Coordinated uterine activity Maturation of the fetus Maternal lactation Progressive cervical dilation 11/21/2018

Uterine Activity During Pregnancy Inhibitors Progesterone Prostacycline Relaxin Nitric Oxide Parathyroid hormone-related peptide CRH HPL Quiescence Uterotrophins Estrogen Progesterone Prostaglandins CRH Activation Uterotonins Prostaglandins Oxytocin Stimulation Involution Oxytocin Thrombin 11/21/2018

Initiation of labor Oxytocin Peptide hormone Hypothalamus-posterior pituitary Fetal production Maternal serum increase in second stage of labor Oxytocin receptors Fundal location 100-200 x during pregnancy Actions Stimulate uterine contractions Stimulate PG production from amnion/decidua 11/21/2018

Initiation of Labor Fetus Sheep Humans Fetal ACTH and cortisol Placental 17 α hydroxylase  Estradiol  Progesterone Placental production of oxytocin, PGF2 α Humans Fetal increased DHEA Placental conversion to estradiol Increased decidual PGF2 and gap junctions Increased oxytocin and PG receptors Decreased progesterone receptors 11/21/2018

The physiology of uterine activity the miometrium is composed by muscular tissue the muscular content decreases towards the cervix so that muscle forms no more than 10% of cervical tissue

Biochemistry of muscle activity the contraction is based on the interaction of myosin and actin which is effected by enzymatic phosphorilation of the light chain of myosin the phosphorilation in catalized by the enzyme kinase which is activated by Calcium. Calcium binds to calmodulin wich activates miosin light chain kinase

Uterine contractions cAMP + Oxytocin + Prostaglandin Oxytocin receptor Extracellular Calcium channel Intracellular Phospholipase C cAMP Ca+ MLCK Ca store + Oxytocin + Prostaglandin Oxytocin binds receptor and activates phospholipase c. PHC increase intracellular Ca by release of intracellular calcium and promote influx of calcium. Ca binds myosin light chain kinase Uterine contractions 11/21/2018

Effect of calcium Agents that act on myometrial muscle cells to cause an increase in Calcium –promote contraction Conditions that cause a decrease in Calcium favor relaxation Calcium antagonist as nifedipine are tocolytics Calcium administration may help uterine contraction

Muscle fibre contraction In the presence of estrogen, an impulse alters the electric potential of the cell membrane and permits the entry into the contractile fibril of sodium and calcium ions, which start the energy-releasing cycle This pulls the actin fibrils into the spaces between the myosin fibrils

Caracteristics of myometrial contractions the uterus functions as a single muscular organ uterine muscles are never completely relaxed (between contractions there is a restingtone of 6-12 mmHG) the frequency of contraction is expressed as the number per unit of time The Montevideo Units are the product of intensity and frequency over a 10 minute period and they give a measurement of uterine activity

Montevideo Research of uterine contraction

True labor Contractions at regular intervals Intervals gradually shortens Intensity gradually increases Minimum 2 contractions in 10 min No response to antispastic drugs

cardiotocograph to measure the uterine acivity internal/external

The “pacemaker” is located at the junction of the Fallopian tube and uterus, on each side. In each woman, one of them is dominant , and it is from there that all contractile waves originate.

in the second stage of labor, voluntary contractions of the diaphragm and abdominal muscles, added to the uterine contraction, propels the baby downwards, through the dilated cervix and vagina. uterine activity continues unaltered after expulsion of the fetus and leads to the expulsion of placenta.

Normal labor and delivery The mechanism by which human parturion is initiated spontaneously, either at term or preterm, is NOT KNOWN it is not possible to determine when labor will begin

Uterine phases of parturition Phase 0 – the prelude of parturition Phase 1 – the uterus is getting ready for labor, when functional changes in myometrium and cervix are required (last days of pregnancy) Phase 2 – the period of active labor : the uterine contractions that bring about progressive cervical dilatation, fetal descent and delivery (the 3 stages of labor) Phase 3 – parturient recovery takes place

The phases of parturition should not be confused with the clinical stages of labor UTERINE QUIESCENCE 95% of pregnancies Can be some uterine contractions, low intensity, brief duration There is no cervical dilation Near the term, Braxton=Hicks contraction/ false labor especially at multipara The uterine smooth muscle does not respond to stimuli

PHASE 1 PREPARATION FOR LABOR Myometrial tranquility is suspended= uterine awakening or activation Cervical modifications during phase 1= invasion by inflammatory cells, like inflammation Softening of the cervix= ripening Factors: prostaglandins E2, F2 α, cytokines Collagen breakdown We use prostaglandin gel to ripe the cervix Cervical ripening is an essential step of labor Cervical dystocia !

PHASE 1 PREPARATION FOR LABOR MYOMETRIAL CHANGES Alteration in expression of key proteins that control myometrial contractility Contraction associated proteins= CAPs Striking increase in myometrial oxytocin receptors and gap junctions

Uterine contraction are painful=unique phenomenon Cause of the pain is not known Hypoxia of contracted myometrium ( as in angina pectoris) Stretching of the cervix during dilatation( highly sensitive area) Stretching of peritoneum over the fundus Compression of the nerve ganglia in the cervix and lower uterine segment/ paracervical infiltration with anestethic produces relief of pain Mechanical stretching of the cervix increase uterine contraction( Fergusson reflex)

CERVIX 2 MAJOR CHANGES Effacement and dilatation Effacement shortening of the cervical canal from a length of 4 cm to a circular orifice with paper-thin edges

CERVICAL DILATATION 2 phases latent phase and active phase Latent phase the durate is variable Active phase acceleration maximum slope deceleration

FRIEDMAN

Labor stages First stage – onset of labor to complete dilatation Latent phase – onset to rapid cervical change Active phase – rapid cervical change to complete dilatation Second stage Third stage Fourth Stage Nulliparous Multiparous Mean 95th % tile %tile Latent phase 7.3-8.6hr 17-21 hr 4.1-5.3hr 12-14 hr Active phase 1.5cm/hr 1.2cm/hr 11/21/2018

Labor stages First stage – onset of labor to complete dilatation Second stage – complete dilatation to delivery of neonate Third stage Fourth Stage Nulliparous Multiparous Mean 95th % tile %tile No epidural 53-57 min 122-147 17-19 57-61 Epidural 79 min 185 min 45min 131min 11/21/2018

Labor stages First stage – onset of labor to complete dilatation Second stage Third stage Delivery of the placenta Mean – 6 minute 97th% < 30 minutes Prolonged EBL >500 Need for D&C Drop in HCT by 10% 11/21/2018

Maternal factors Uterotropin= agents that prepares the uterus Uterotonin=uterine smooth muscle contractant Oxytocin- number of receptor increases in labor Prostaglandins Endothelin 1 Miometrial cell - Calcium

Fetal factors In late pregnancy the fetal pituitary produces ACTH and oxytocin These 2 hormones may be involved in the coordinated rhytmic uterine contraction which caractherizes labor

If induction of labor fails Postdate pregnancy Chronic fetal distress Placenta fails Can lead to fetal death After 41/42 weeks induction of labor by oxytocin/ prostaglandin gel

The physiology of the puerperium Puerperium is defined as the period after birth During this time, the reproductive tract returns anatomically to a normal nonpregnant state, and in most women who are not breast feeding, ovulation is reestablished

Classification Early puerperium : 4 hours after childbirth The veritable puerperium : 10 days after childbirth Late puerperium: 30 days after childbirth

Early puerperium= 4 hours The woman rests in the delivery room Pulse and blood pressuse must be observed The form and consistance of the uterus must be checked out The Pinard’s globus is firm and globulous due to contraction and retraction of the uterus Blood loss is about 250 ml

The veritable puerperium > 4 hours – 10 days Specific phenomena - involution of the uterus - the lochia - lactation Modifications of the organs and systems

Involution of the uterus immediatly after placental expulsion, the fundus of the contracted uterus is slightly below the umbilicus the process by which the uterus returns to nonpregnant state is known as “involution” the uterus reduces by about 1-1,5 cm / day fundal height is measured each day failure of involution suggests retained placental tissue

The lochia Early in puerperium, sloughing of decidual tissue results in a vaginal discharge of variable quantity, this is termed LOCHIA It is made by erythrocytes, shreds of decidua, epithelial cells and bacteria. Foul-smelling is suggestive of infection=endometritis The quantity of the lochia varies from day to day and the total quantity in 1000 ml.

T the obstetrician

“lochia rubra” - first few days “lochia serosa” - after 3-4 days “lochia alba”- after 10 days

Lactation during pregnancy the breasts develop due to the increasing of estrogen and progesterone estrogen leads to an increse both in size and number of the duct system progesterone appears to increse the number of alveolar cells during lactation, there is a decrease in the amount of adipose tissue relative to glandular tissue, and the size and the weight of the breasts increases

during pregnancy the breasts secrets colostrum it is a yellowish fluid, containing a much greater quantity of proteins than normal milk, plus desquamated endothelial cells it’s gamma-globulin content may be a prevision for the supply of antibodies

following child birth and placental expulsion, the estrogen levels fall within 3 days, permitting prolactin to act , and to initiate lactation. neurohypophysis releases oxytocin by reflex suckling the oxytocin causes contraction of the myoepithelial cells and ejection of the milk

for the maintenance of lactation suckling is essential and it is also necessary to have normal levels of : - ACTH - growth hormone - thyroid hormone - insulin the major components of milk are proteins, lactose, water and fat all vitamins, except vitamine K are found in the human milk but in variable amounts.

Breastfeeding is GOOD BENEFITS FOR MOTHER BENEFIT FOR CHILD

Changes in the cervix and vagina immediatly after the third stage of labor, the cervix and the lower uterine segment are thin, collapsed, flabby structures the outer margins of the cervix is usually lacerated, especially laterally the cervical opening contracts slowly for a few days immediately after labor by the end of the first week it has narrowed to a one-finger diameter as the cervical opening narrows, the cervix thicknes and the canal is reformed

Vagina and vaginal outlet early in puerperium, the vagina form a capacious, smooth-walled passage that gradually diminishes in size but rarely returns to nulliparous dimensions the hymen is represented by several small tags of tissue, which during cicatrization are converted into myrtiform caruncles characteristic to parous women

Changes in urinary tract in the first few hours after delivery micturition may be difficult, partially because of reflex suppresion of detrusor activity and sphincter spasm during the first 1 or 2 days a marked diuresis occurs, because of a fall in progesterone content of the blood and the alteration of cell metabolism to the non-pregnant state

Blood marked leukocytosis occurs during and after labor (sometimes reaching 30000 per ml) there is also a relative lymphopenia and an absolute eosinopenia normally, during the first few postpartum days, hemoglobin, hematocrit and erythrocyte counts fluctuate moderately by one week after delivery, the blood volume has returned to almost its nonpregnant level

Bowel function constipation has become much less of a problem in the puerperium routine prescription of a stool softener is a common practice

Late puerperium Following vaginal delivery the hospitalization is warranted for 72 hours Before discharge, the woman should receive instruction concerning the anticipated normal physiological changes of the puerperium, including changes in lochia patterns, weight loss due to diuresis and whan to expect milk let down

Restoration of ovulation and menstruation the more frequently the child suckles, the higher is the plasma prolactin level and the longer ovulation is delayed however, some lacting women, especially those who only partially breast-feed, ovulation may occur, and subsequently pregnancy without any menstrual period ovulation is unusual among lactation women for about 20 weeks

Menstruation may start earlier: - 10% of breast feeding women menstruate by the 10-th week after birth - 40% by 20 weeks - 50% by 30 weeks

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