THE BONNY PELVIS AND FETAL SKULL, PRECONCEPTION AND CONCEPTION

➡️ Midwifery-1

CLASS OBJECTIVES:

At the end of session you should be able to;

Give introduction of bonny pelvis and fetal skull.

Describe the bonny pelvis and fetal skull and their relationship during labour.

Introduction:

Knowledge of the shape and dimensions of the normal female pelvis is essential for a proper understanding of the second stage of labour and its abnormalities since the body pelvis is an important component which determines the birth canal structure.

Cont:introduction:

The human female pelvis shows adaptations that are of obstetric advantage and relate also to the relative ―big‖ head of the foetus.

These adaptations develop chiefly in childhood and puberty.

THE BONY PELVIS

2 Innominate bones : -Illium -Ischium -Pubis

1 Sacrum

1 Coccyx

Four different types of pelvises

Gynaecoid pelvis
Android pelvis
Athrapoid pelvis
Platypelloid pelvis

GYNECOID PELVIS:

Typical female pelvis found in 50% of women

Rounded—slightly oval inlet

Straight pelvic sidewalls with roomy pelvic cavity

Good sacral curve

Ischial spines are not prominent

Pubic arch is wide

greater sciatic notch

Sub-pubic arch rounded

ANDROID PELVIS

Male-type pelvis favouring OP positions and apt to cause deep transverse

Pelvic brim is heart shaped

Pelvis funnels from above downwards (convergent sidewalls)

Sub-pubic arch very narrow(gothic arch)

Prominent spines

22.4% of women

Long-cone funnel pelvis

Oval obturator foramen

ANTHRAPOID PELVIS

25% white women & 50% nonwhite

Pelvic brim APD > TD

Long & narrow pelvic canal with long sacrum

Straight pelvic sidewalls

PLATYPELLOID PELVIS

Pelvic brim TD >APD

kidney shaped

Sacral promontory pushed forwards

Clinical Assessment

Body build

Gynaecoid Anthrapoid Android

WHAT IS THE PELVIC BRIM?

It is the inlet of the pelvis which divides the pelvic cavity into false & true pelvis

It is formed by the sacral promontory, ala of the sacrum, arcuate line of the ilium, iliopubic eminence, pictineal line of the pubis, pubic crest & symphesis pubis

The plane of the brim is 55-60 ° above the horizontal

Anterioposterio diameter

It is a line from the sacral promontory to the upper boarder of the symphysis pubis.

When the line is taken to the upper boarder of the symphysis pubis it is called the Anatomical conjugate and is measures 12 cm,

When it is taken to the posterior boarder of the upper surface 1.25 cm lower is called Obstetrical conjugate and measures 11 cm, it represents the available space for the passage of the fetus.

Cont’

The diagonal conjugate is measured from the lower boarder of the symphysis pubis to the sacral promontory it may be estimated on vaginal examination as part of pelvic assessment and should measure 12-13 cm.

Oblique diameter

It is a line from one sacroiliac joint to the iliopectineal eminence on the opposite side and measures 12 cm.

There are two diameters, left and right oblique diameters each takes its name from the sacroiliac joint from which it arises.

Transverse diameter

It is a line between the points further apart on the iliopectineal line and measures 13cm.

Another diameter is measured, the sacrocotyloid diameter from the sacral promontory to the iliopectineal eminence on each side and measures 9-9.5 cm.

It is only important in posterior positions of the occiput.

The pelvic cavity

The cavity extends from the brim above to the cavity below.

The anterior wall is formed by the pubic bone and the symphysis pubis and is 4 cm long.

The posterior wall is formed by the curve of sacrum and is 12 cm long. Its lateral walls are the sides of the pelvis

The cavity is circular in shape its diameters cannot be measured but are considered to be 12 cm.

THE PELVIC OUTLET

Two outlets are described, the anatomical and obstetrical.

The anatomical outlet is formed by the lower border of the pelvic bones and the sacrotuberous ligaments.

The obstetrical outlet is the space between the narrow pelvic strait and the anatomical outlet.

The narrow pelvis strait lies between the sacrococcygeal joint, the two ischial spines and the lower boarder of symphysis pubis.

There are three diameters:

The anteroposterior diameter

It is a line from the lower boarder of the symphysis pubis to the sacrococcygeal joint

It measures 13 cm. the coccyx may be deflected backwards during labour.

The Diameter indicates the space available during delivery.

Cont’

The oblique diameter

Between the obturator foramen and the sacrospinous ligaments there are no fixed points the measurement is taken to be 12cm.

The transverse diameter

This is a line between the two ischial spines and measuers 10-11 cm it is the

narrowest diameter in the pelvis.

In Gynaecoid & Android pelvis

distance between ischial spine to brim

is 5 cm.

In Anthropoid pelvis distance is 7 cm

In Platypelloid pelvis distance is 3

Station of the head in relation to ischial spines

Pelvic joints

Relationship of fetal skull to pelvis Axis of birth canal

90 rotation for Occipital-transverse

when engaging

diameter is at the brim . Occiptio-oblique in midcavity.Occipito-anterior at ischial spine

Promontory Symphysis pubis

Sacral promontory

Left sacro-iliac joint

Iliopectineal line

Sacrospinous ligament

Sacrotuberous ligament

Symphysis pubis

Ischial spine

Ischial tuberosity

PELVIC WALLS

The inner aspect of the bony pelvis is covered with muscles

Above the brim --- iliacus & psoas

Sidewalls ---- obturator internus & its fascia

Post wall ---- pyriformis

Pelvic floor ---- lavator ani & coccygeus

PELVIC LIGAMENTS

Ligaments

Sacrospinous ligament

lateral aspect of the sacrum to ischial spines

Sacrotuberous ligament

lateral aspect of the sacrum to inner aspect of ischial tuberosity

Sacroiliac ligament

medial surface of the ilium to sacrum

lliolumbar ligament

iliac crest to transverse lumbar vertebra

☑️ WHAT IS MEANT BY CLINICALLY FAVORABLE PELVIS?

1.Sacral promontory can not be felt

2. Ischial spines are not prominent

3. Subpubic arch accept 2-3 fingers

4. Intertuberous diameter accept 4 knuckles on pelvic exam

The fetal skull contains delicate material which may be subjected to great pressure as the head passes through birth canal.

It is large compared to the true pelvis and some adaptation between skull and pelvis must take place during labour.

The head is the most difficult part to deliver whether it comes first or last.

Cont:fetal skull:

The midwife must understand the important land marks and measurements of the fetal skull as to recognize normal presentations and positions and to facilitate delivery with the least possible trauma to the mother and baby.

Where there is malpresentation or disproportion exists she will be able to identify and alert the medical staff.

Ossification:

The bones of the fetal head originate in two ways. First the face is laid down in cartilage and is almost completely ossified at birth ,the bones being fused together and firm.

Second: the bones of the vault (head) are laid down in membranes and are much flatter and more pliable. They ossify from the centre outwards and this process is incomplete at birth leaving small gaps which forms the sutures and fontanelles.

The ossification center of each bone appears as a boss or protuberance.

🔷Five main bones in the vault:

There are:

2 parietal bones

2 frontal bones

1 occipital bone

🔷Two main Fontanelles:

1.Anterior fontanel or bregma: found at the junction of sagittal, coronal and frontal sutures. It is broad diamond shaped and recognizable vaginally because the suture leaves from each corners. 3-4cm long,1.5-2cmwide normally closes by the time the child is 18months of age.

2.The posterior fontanels or lambda: situated between the lambdoidal and saggital sutures. Small triangular in shape and can be recognized vaginally because a suture leaves from each of the three angles, closes at 6 weeks of age after delivery.

🔻MOULDING OF THE HEAD

Bones of vault are compressible

Molding can decrease biparietal

Bones of base of skull are incompressible diameter by 1cm

Occurs with descent of the fetal head into the pelvis to reduce the head circumference

Frontal bones slip under parietal bones

Parietal bones override each other

Parietal bones slip under the occipital bone

🔻DEGREE OF MOULDING

Assessed vaginally

0- suture lines are separate

+1- suture lines meet

+2 - suture lines overlap but can be reduced by gentle digital pressure

+3- overlap and Irreducable

➡️ PRECONCEPTION AND CONCEPTION

1. PREPARING FOR PARENTHOOD

Parenthood education:

-This is any interaction between the midwife and the mother or parents when the matters related to child birth and parenting are discussed, this covers antenentally and postnatally.

Factors affecting learning:

1) MOTIVATION:

something special is happening to these mothers lives. They are hungry to satisfy their needs to understand themselves and gain the knowledge and skills required in order to cope with the caring experiences and responsibilities.

Each mother wants to secure her feelings/thoughts about reality of child growth within her womb.

She need to feel secure about her place of delivery she will desire to learn very quickly how to care for and nurture her off spring.

2. ACCURATE INFORMATION:

Mothers need to trust midwives in giving them accurate and up to date information's.

Insufficient information will not aid their growth and may jeopardize their faith in other midwives.

3) PRESENTATION:

The presentation of the information affects the learning.

Midwives need to give information in a way that interests the mothers and their partners.

4) ENVIRONMENT:

Physical comfort and emotional state affects the attention one can give.

Attend the physical needs first.

No noise (quiet place)

Health in pregnancy:

1) Diet in pregancy:

It is important in three aspects (accounts).

Health for woman herself.

Her developing fetus.

Alleviating minor disorders of pregnancy.

2) ALCOHOL:

In advisability of drinking alcohol while pregnant has received much press coverage.

No safe level of alcohol consumption has been established .

Therefore it is wise to stop drinking alcohol prior conception.

3) SMOKING:

Smoking could be a response to stress:

If the woman can stop smoking, the outlook of herself and the fetus is improved.

If this proves to be very difficult, she could try to cut down.

Smoking is linked with:

Intrauterine growth retardation.

Pre-term labour.

Increased in the perinatal mortality rate.

Increased risk of chest infections and thrombo-embolic to the mother.

Cont:Health in pregnancy:

4) SEXUAL INTERCOURSE:

Sometimes couple fears that sexual intercourse during pregnancy may harm the baby.

It is absolutely safe and normal ,unless special conditions pertain.eg women with shirodiker suters,threatened abortions,Vaginal infections.

Cont:Health in pregnancy:

If women is nauseated in early pregnancy she may feel disinclined to have intercourse but the couple can be encouraged to find other ways of being loving.

If mother has history of miscarriage ,she should avoid intercourse in the early months.

Cont:Health in pregnancy:

5) EXERCISES AND SPORTS:

I f a mother is used to regular exercises such as walking ,swimming,riding,or cycling, there is no reason why she should not continue for as long she feels comfortable.

Cont:Health in pregnancy:

6) TRAVEL:

-Travelling is sometimes unavoidable in pregnancies. In forced families airline,ask for doctors certificate starting that a pregnant woman is fit to travel and they prefer not take ladies beyond 32nd week. Mother can do fly safely before this time.

Cont:Health in pregnancy:

7) CLOTHING:

This reflects the mothers state and financial position but loose cool clothing will be the most comfortable.

-Pregnant woman gets bored with their maternity dressing.

Cont:Health in pregnancy:

-Advice them to put on low ,flat shoes .they must avoid high heels.

they predispose to back ache .

May cause trauma due to falling down as weight increases and loose balance

while walking esp.in multiple pregnancies.

🔻MINOR DISORDERS OF PREGNANCY:

Minor disorders are not threatening.

-May continue and become a serious complications.

-Pregnancy where sickness develops into hyper emesis gravidaram, a condition which began as a minor disorder, has become a life-threatening abnormality.

cont:minor disorders of pregnancy:

Digestive system:

(1) Nausea and vomiting:

-Present between 6 – 16 weeks gestation.

-Hormonal influences are cited as the most likely cause.

-Human chorionic gonadotrophic is found in large amounts until the placenta takes over from the corpus luteum at around 12 weeks

-Oestrogen and progesterone are also contributors, the transient nausea which may occur when a woman takes the contraceptive pills cooperates this.

If vomiting becomes severe the mother may loose weight and become dehydrated and ketotic.

2) Heart burn:

-Progesterone relaxes the cardiac sphineter of the stomach and allows reflux of gastric contents into the oesophagus.

-Heart burn is troublesome at about 30-40 weeks gestation because at this stage the stomach is under pressure from growing uterus.

3) Excessive salvation:

This occurs from 8th week gestation.

Caused by hormones of pregnancy.

May be accompanied with heartburn.

4) Pica:

This is the term used when the mother craves certain food or un-natural substances such as charcal,soil.

-The cause is unknown but hormones and changes in metabolism are blamed.

5) Constipation:

-Progesterone causes relaxation and decreased peristalsis of gut which is also displaced by the growing uterus.

It is helpful to increase the intake of water, fresh fruit ,vegetables, and whole meal foods in the diet.

-A glass of warm water in the morning, before tea or break fast may activate this gut and help regular bowel movement.

Exercise is helpful, especially ,walking.

Constipation is sometimes associated with taking of oral iron.

Musculoskeletal system:

1) Backache:

The midwives role is to educate the mother to understand her changing center of gravity as the fetus grows and which postures to adopt. The hormones sometimes soften the ligaments to the degree that support is needed.

Cont:Musculoskeletal system:

2) Cramp:

The cause of leg cramp in women is unknown. It may be due to ischemia or result from changes in the PH or electrolyte status.

It may be, help to make gentle leg movements whilst in a warm bath prior to setting for the night. This enhances

circulation and removes waste products

from muscle.

Genito-urinary system:

1) Frequency micturation:

This occurs in the early weeks of pregnancy, when the growing uterus is still situated Within the pelvis and competes for space required by the bladder .

In the latter weeks the head usually enters the pelvis and reduced the space available.

Cont:Genito-urinary system:

2) Leucorrhoea:

This is the term used for the increased white non-irritating vaginal discharge in pregnancy.

If the mother finds the discharge in pregnancy give advice on personal hygiene.

Circulatory system:

1) Fainting:

In early pregnancy fainting may be due to

vasodilatation occurring under the influence of progesterone before there has been a compensatory in blood volume.

Cont:Circulatory system:

Avoiding long periods of standing is helpful and being quick to sit or lie down if she feels slightly faint.

Later in pregnancy the mother may feel fainting when lying flat on her back ,the weight of uterine contents press on the inferior vena cava and shows the return of blood to heart.

Cont:Circulatory system:

2) Varicosities:

-Progesterone relaxes the smooth muscle of the veins and results in sluggish circulation .

-The valves of the dilated veins become inefficient and varicosities result varicose veins may occur in the legs, anus, (hemorrhoids) and vulva.

Skin:

Skin changes include linear nigra and the areola of the breast.

-Chloasma may occur, this is a butterfly shaped area of pigmentation over the face ,the mother may be reassured that this will diminish as soon as the baby is born.

-Sometimes there is generalized itching which often starts over the abdomen.

Nervous system:

1)Carpal tunnel syndrome:

-The mother complains of numbness and pins and needles in her fingers and hands. This usually happens in the morning but it can occur at any time of the day.

It is caused by fluid retention which creates oedema and pressure on the

median nerve.

Cont:Nervous system:

-Wearing a splint at night with the hand resting high on two or three pillows sometimes brings relief.

-Carpal tunnel syndrome usually resolves spontaneously following delivery.

Cont:Nervous system:

2) Insomnia:

-Physical reasons for sleep disturbance

-Nocturnal frequency, Difficulty in getting comfortable bed due to the growing fetus.

-The increased blood supply to the uterus on lying down sometimes causes the baby to move a lot, just as the mother wishes to sleep.

-She may go to bed earlier in the hope that the baby will have an active time earlier and allow mother to sleep when she wants to.