Obstetrics Flashcards
Internal Genital Development
Develop from the Paramesonephric (Müllerian) System, becoming the uterus and fallopian tubes. Undifferentiated testes become ovaries, and the urogenital sinus becomes the vagina.
Histology of the vagina
Squamous stratified epithelium until the external os
Histology of the cervix
Simple columnar epithelium, beginning at the squamocolumnar junction at the external os. Lined with small, irregular crypts.
Ligaments of the Uterus/Ovaries (7)
- Round ligament (NOT SUSPENSORY, helps keep it anteverted) - attaches to proximal fallopian tubes, go around inguinal canal, end up in labia majora
- Uterosacral ligament (Suspensory, has PNS/SNS innervation) - begins at sacrum, inserts into posterior uterus at isthmus
- Cardinal Ligaments (Suspensory) - lateral uterus to lateral pelvic wall
- Pubocervical Ligaments - pass anteriorly around the bladder to the posterior pubic symphysis
- Broad Ligament - sheet of peritoneum covering ovaries and uterus
- Infundibulopelvic Ligament (NOT SUSPENSORY, contains ovarian aa, vv, nerve plexus and lymphatics) - from ovaries to the pelvic wall, part of the broad ligament
- Ovarian Ligament (Suspensory) - attaches ovary to the base of the fallopian tubes.
Peritoneal folds around the Uterus/Ovaries (5)
- Vesicouterine fold (between bladder and uterus)
- Pouch of Douglas (rectouterine fold, behind uterus)
- Mesometrium (Common stalk of peritoneum going up)
- Mesosalpinx (Fold off the mesometrium covering the fallopian tube)
- Mesovarium (fold off the mesosalpinx covering the ovary)
Histology of the Fallopian Tubes
Lined with ciliated, folded columnar epithelium
Blood supply of the ovary
Ovarian arteries come off the abdominal aorta, just underneath the renal aa, come through the infundibulopelvic ligaments to the ovary
Ovarian veins - L drains into the L renal vein, R goes into the IVC
Blood supply of the Fallopain tubes, uterus, and vaginal canal
Ovarian artery supplies part of the fallopian tube
Internal iliac –> Uterine artery –> Ascending and descending uterine arteries –> Uterus and fallopian tubes (Anastomosis with ovarian aa)
Uterine aa –> Vaginal branch of uterine aa –> Superior vaginal canal (anastomosis with uterine aa)
Inferior pudendal aa –> Inferior vaginal canal
Venous drainage follows arterial supply
Most commonly used surgical incisions in Gynaecological Surgery
Pfannenstiel Incision (Horizontal incision just above the pubic symphysis) - cosmetically appealing
Maylard (transverse) Incision (Horizontal incision between both ASIS) - bigger access, decent cosmesis
Median or Paramedian incision (Vertical down linea alba or just beside it) - for extensive procedures that may require abdominal exploration (e.g. ovarian cancer)
Phases of the Female Reproductive Cycle
The Follicular Phase (from menses to ovulation, consists of menstrual phase and proliferative phase)
The Luteal Phase (from LH spike/ovulation until just before menses)
Hormonal Changes during the Follicular Phase
Dropping levels of oestrodiol and progesterone lead to menses (as the lining is not maintained/arteries constrict), and a rise in FSH (mainly) and LH levels. Stimulates theca cells and granulosa cells in the ovary to produce E1 and E2, which have negative feedback loop on hypothalamus
Hormonal Changes during Ovulation
As oestrodiol levels rise to a critical level (>200 picograms over 50 hours), this switches it to a positive feedback loop, boosting LH and FSH levels. 36-44 hours later, ovulation occurs.
Hormonal Changes during the Luteal Phase
The Corpus Luteum (CL) produces oestrodiol and progesterone, promoting endometrial growth and development, as well as inhibiting the hypothalamus and pituitary gland. If pregnancy occurs, the CL is “rescued” by hCG released from the placenta, promoting further progesterone release - otherwise, the CL dies, and the cycle begins again, with dropping progesterone levels leading to artery constriction in the endometrium and menses begins.
Steroid Hormone Pathways
Cholesterol
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Pregnenolone –> Progesterone – … –> Aldosterone
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17-OH Pregnen. –> 17-OH Progesterone –…–> Cortisol
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DHEA –> Androstenedione –> Estrone (E1)
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Androstenediol –> Testosterone –> Estradiol (E2)
Early Development of Oocytes/Follices (before Puberty)
Peak numbers of oocytes at 20 weeks (6-7 mill), drops to 1-2 million at birth. Granulosa cells surround the oocytes to form the primordial follicle with a zona pellucida. These oocytes are arrested in Meiosis I at birth.
Development of Oocytes/Follicles from Puberty to Ovulation
At puberty, these follicles grow and develop, forming primary follicles.
Each cycle, these develop rapidly, forming a corona radiata and antrum (space), stimulated by high FSH levels. “The dominant follicle” is usually oestrogen-dependent, and becomes more and more sensitive to FSH, developing LH receptors on the granulosa cells just before ovulation.
The oocyte finish Meiosis I just before ovulation, producing the first polar body, and are then arrested at Meiosis II each month.
Oocytes/Follicles from Ovulation to Fertilization and Implantation
LH surge at ovulation causes proteolytic enzyme release, leading to dissolution of the follicle wall and release of the oocyte, zona pellucida and corona radiata onto the surface of the ovary. Here, it is picked up by the fallopian tube’s muscular movements and ciliary action, where it travels down into the tube, and is fertilized.
Just before fusion of male and female pronuclei, Meiosis II is completed, and the second polar body forms, giving the egg 23 single chromosomes.
Histophysiology of the Endometrium - layers and phases (3)
Divided into two layers - the funcitonalis (outer portion, has spiral arteries, sloughed off at menstration) and the basalis (has basal arteries and stem cells, minimal changes during the cycle)
Proliferative phase - endometrial proliferation from oestrogen, endometrial glands lined with pseudostratified columnar cells grow, and spiral arteries develop.
Secretory Phase - progesterone stimulates the glandular cells to secrete mucous, glycogen, and other substances - makes them tortuous and dilated. Stroma is oedematous.
Menstrual Phase - drop in oestrogen and progesterone (if no pregnancy) leads to constriction of arteries and tissue involution - becomes necrotic and WBC infiltrated, with RBC extravasation and sloughing off.
Spermatogenesis
Primordial Germ Cell
(Mitosis)
Primary Spermatocyte (Diploid) x1
(Meiosis I)
Secondary Spermatocyte (Haploid) x2
(Meiosis II)
Spermatid (Haploid) x4
(Develops to)
Sperm Cell (Haploid) x4
Sperm Capacitation
A process that allows the sperm to be able to fertilize in vivo.
Involves disinhibiting the acrosome of the sperm by it swimming free of seminal fluid.
Sperm Acrosome
A modified lysosome lying over the sperm head that allows penetration of the layers of the egg (ZP, CR) and moving the nucleus into the oocyte.
Timeline from fertilization to implantation
Immediately - once the sperm nucleus enters the oocyte, cortical granules inside the oocyte cause changes in the ZP to make it impenetrable to other sperm.
Day 1 - Pronuclear migration
Day 3 - Fusion of the pronuclei to form a zygote, begins divisions
Day 3-4 - Formation of a 16+ cell morula, and compaction of the morula (formation of desmosomes and tight junctions). Blastula forms.
Day 5 - Blastula cells migrate into cavity, forming a trophoblast, and the whole thing becomes a blastocyst. “Hatching” of the blastocyst from the ZP.
Day 7 - Implantation of the blastocyst into the endometrial wall.
Events after implantation
Blastocyst embeds into the endometrial wall, becoming surrounded by endometrial tissue.
Day 8 - Trophoblast begins to differentiate into the syncytiotrophoblast (conjoined, multi-nucleated cell) and the cytotrophoblast (reminant of the trophoblast), with the former beginning to invade into tissue, absorbing endometrial cells that have swelled from glycogen and lipids, and producing hCG. The embryonic disk differentiates into a hypoblast and an epiblast, with an amniotic sac developing in the epiblast.
Day 10 - continued development of the bilaminar disk, producing a amnionic sac and a yolk sac. Syncitiotrophoblast continues to invade, developing lacunae that fill up with maternal blood
Day 12 - primary chorionic villi form, and foetal circulation begins to become established.
The decidual reaction
The process that endometrial cells undergo to prepare for foetal implantation - swelling as they fill up with glycogen and lipids for foetal nutrition.
The Foetal adrenal gland (anatomy and function)
Consists of:
- Outer (Definitive) Zone - Secretes glucocortioids and mineralocorticoids, later becomes the 3 zones seen in adults (fasciculata, glomerula, and reticularis)
- Inner (Foetal) Zone - Comprises 80% of the gland, primarily secreting androgens, losing function at delivery and disappears after first year of life.
- Adrenal medulla - Synthesizes and stores catecholamines
Endocrine role of the placenta
- Releases corticotrophin releasing hormone (CRH)
- Produces progesterone and cortisol (takes over from the corpus luteum)
- Produces oestrogens - lacks 17α-hydroxylase, so cannot synthesize them from progesterone, instead using foetal androgens
hCG
Human Chorionic Gonadotrophin (hCG) is secreted by trophoblastic cells of the placenta, maintains the corpus luteum for first 6-8 weeks, also suppressing maternal immune system (increasing T-regulatory cells)
Rises after 8th day of pregnancy, peaks at week 6-12, should double every 2 days in the first few weeks of pregnancy.
CRH
Corticotrophin-Releasing Hormone (CRH) is produced by the placenta to stimulate release of foetal ACTH, leading to placental production of oestrogen from DHEA-S.
Plays a role in activation and progression of labour, and is suppressed by progesterone.
Oestriol (E3)
Most abundant oestrogen found in pregnancy
Cortisol
Promotes differentiation of Type II alveolar cells, bioproduction of surfactant into alveoli, and helps release CRH and prostaglandins before labour.
Oxytocin
Originates from the supraoptic and paraventricular nuclei in the maternal hypothalamus, released from the posterior pituitary in response to mammary stimulation and birth canal stretch. Results in uterine contractions.
Short half life of 3-5 minutes.
Prostaglandins and Leukotrines
Produced locally in the uterus, placenta and foetal membranes - help decidualization, cervical ripening before labour, and contraction of the uterus. This is why local infection (UTI, endocervical, etc) can induce premature labour.
PGE2 also helps keep the ductus arteriosus open, and so NSAID use during pregnancy can result in DA closure, foetal pulmonary hypertension and death.
Stages of Parturition
1 - Activation
Trigger comes from uterine stretch from foetal growth, as well as a surge of cortisol coming from the foetal HPA axis. Cortisol also triggers SP-A (lung surfactant) release from the lungs into the amniotic fluid, signalling that the lungs are mature (last organ to do so)
2 - Stimulation
Positive feedback loop set up between placental CRH release and foetal cortisol. This promotes prostaglandin production. In the myometrium, ratio of progesterone receptors shifts towards PRA (progesterone insensitive) and away from PRB, reducing progesterone’s inhibitory effects, and promoting oestrogen receptor ERα. Oestrogen’s effects include increasing oxytocin receptors, increasing prostaglandin receptors, promoting the actions of phospholipase C (producing inositol triphosphate –> calcium release from SR) and COX-2, and promoting gap junction production.
3 - Involution
As the foetus leaves the uterus, there is a massive surge of oxytocin (thought to be from foetal head compression), promoting uterine contraction to stem bleeding.
Weak contractions before parturition (name and mechanism)
Braxton-Hicks contractions are weak and not co-ordinated, occur 4-8 weeks before labour, and are due to a lack of gap junctions between muscle cells, and inadequate disinhibition of progesterone and stimulation by prostaglandins and oxytocin. DO NOT AFFECT CERVICAL EFFACEMENT AND DILATATION.
Supine Hypotensive Syndrome
Occurs in 10% of women, caused by drop in blood pressure when supine, as the uterus compresses the IVC, without any compensatory increase in peripheral vascular resistance. Leads to dizziness, nausea, and syncope. Managed by rolling patient to left side.
Poseiro Effect
Foetal distress that may occur when the mother is supine in late pregnancy - the heavy uterus compresses the aorta. Clinically, there is an absence of femoral pulses.
Metabolic Changes during pregnancy (halves)
First half = potentiated anabolic effects of insulin = glycogen storage and synthesis, reduced fasting glucose levels
Second half = insulin resistance = reduced glucose tolerance, increased FFA levels in blood, risk of ketoacidosis rises.
Summary of Maternal changes during pregnancy
Respiratory (5) Cardiovascular (6) Musculoskeletal (2) Endocrine (3) Dermatological (3) Gynaecological (3) Urological (2) Gastrointestinal (3)
Respiratory
- Diaphragm pushed up 4cm
- Increased Tidal Volume
- Increased O2 consumption
- Increased minute ventilation
- Respiratory alkalosis (7.40-7.45)
Cardiovascular
- Increased CO (higher HR and stroke volume)
- Water retention and increased blood volume
- Increased RBC, lower Hb
- Blood pressure lower
- Lower peripheral resistance
- Increased clotting factors
Musculoskeletal
- increased BMI
- Back pain, sciatica, calf cramps
Endocrinological
- Increased thyroid function (hCG)
- Cortisol levels rise
- Human Placental Lactogen
Dermatological
- Increased skin pigmentation
- Distension and proliferation of blood vessels
- stretch marks
Gynaecological
- Breast enlargement and pigmentation
- Uterine hypertrophy/stretch
- Lactobacilli proliferaction in vagina - low pH
Urological
- Increased GFR
- Ureter/collecting system dilatation (progesterone)
Gastrointestinal
- Oesophageal relaxation - Reflux
- Increased intra-abdominal pressure (haemorrhoids, reflux)
- Reduced motility (constipation)
Why does foetal blood have higher affinity for O2 than mother? (2)
- Prescence of HbF
- Higher concentration of Hb
Uterine/Placental flow diagram
Umbilical Artery
- PO2 = 18mmHg
- PCO2 = 55mmHg
- SaO2 = 40%
FLOW = 300-500mL/min, 50% shunt
Umbilical Vein - PO2 = 28mmHg - PCO2 = 45mmHg - SaO2 = 70% \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
Uterine Artery
- PO2 = 100mmHg
- PCO2 = 32mmHg
- SaO2 = 95%
FLOW = 700-1200mL/min, 20% shunt
Uterine Vein
- PO2 = 33mmHg
- PCO2 = 40mmHg
- SaO2 = 60%
Foetal Cardiovascular Structure, their courses, and their adult reminants (5)
Umbilical Vein
- From placenta to ductus venosus
- Becomes ligamentum teres hepatis
Ductus Venosus
- From Umbilical vein to IVC
- Becomes Ligamentum venosum
Ductus Arteriosus
- From Pulmonary Artery to descending aorta
- Becomes ligamentum arteriosum
Foramen Ovale
- From right to left atrium
- Becomes intraventricular septum (closure)
Umbilical Artery x2
- From common iliac arteries
- Becomes the superior vesical arteries
Cardiovascular changes at birth (5) (in order)
1 - Elimination of placental circulation
2 - Vasodilation and reduced resistance of pulmonary vessels –> due to breathing
3 - Closure of foramen ovale –> right pressures < left pressures
4 - Closure of ductus arteriosus –> dropping PGE2, high O2 saturation
5 - Closure of ductus venosus
Immunology of Pregnancy (5 + what isn’t affected)
Uterus decidua
- Absence of B cells
- Increased numbers of T-suppressor cells
Placenta
- Absence of classic MHC I/II molecules on syncytiotrophoblast, only MHC I molecules on trophoblast to help with infection response
- HLA-G suppresses immune system
Vitamin D essential for these functions
Phagocytosis and maternal adaptive immune systems not significantly altered by pregnancy
Timing of Antenatal Visits
1 - week 8-12 (for risk assessment and health optimisation) 2 - week 17-19 3 - 24 4 - 28 5 - 32 6 - 36 7 - 38 8 - 40
The first antenatal visit - Components (4)
- Complete History (inc reproductive, genetic, family, social, nutritional)
- Physical examination (including BP, maternal weight)
- Labs (see other flash card)
- Estimating gestational age and date of confinement (due date)
The first antenatal visit - Labs (13)
- Complete blood count, including Hb (for baseline)
- Blood type and Rhesus factor
- Rhesus Antibody screen
- Pap smear screening (if indicated)
- Glucose tolerance test (if indicated)
- Ultrasound (if indicated)
- Urine dipstick screen - protein, glucose, leukocytes
- Urine culture
- Rubella serology
- Syphilis serology
- Chlamydial culture (if indicated)
- Hep B/C serology
- HIV Serology
Signs of Pregnancy (3 categories)
- Cardiovascular
>Physiological systolic murmur
>S3 (due to hypervolaemia) - Dermatological
>Linea nigra (down from the umbilicus)
>Spider naevi
>Palmar erythema
>Dark discolouration of the vulva and vaginal canal (Chadwick’s sign) - Gynaecological Signs
>Asymmetric enlargement (Piskacek’s Sign)
>Softer uterus (palpate uterus above cervix = Hegar’s sign)
Which vaccines are contraindicated in pregnancy? (5)
- BCG
- Measles
- Mumps
- Rubella
- Varicella
(all are live, attenuated vaccines)
Management of Rh negative pregnant women
RH0 (D) immunoglobulin should be given at 28 weeks, postpartum, and at any point where sensitization may occur (e.g. during a procedure)
Implantation bleeding
Abnormal vaginal bleeding caused by implantation, experienced in 30-40% of normal pregnancies.
Spontaneous Abortion rate
10-15% of recognised pregnancies, however may be as high as 50% of all conceptions, the majority in the first 14 days.
Drops to 3% by the 8th week.
Threatened abortion
Pregnancy complicated by vaginal bleeding before 20 weeks, sometimes with abdominal ache. 25-50% progress to spontaneous abortion. Best managed with US examination - determine viability of foetus, and later to manage the higher risk of preterm birth.
Types of spontaneous abortion (5)
- Threatened abortion
- Inevitable abortion (cramps, bleeding, cervical dilatation)
- Incomplete abortion (above + some products have come down, BEWARE OF SEPSIS AND HAEMORRHAGE)
- Complete abortion
- Missed abortion (When the foetus has died, but is retained, usually for over 6 weeks. Beware of coagulation problems, check fibrinogen until all tissue comes)
- Recurrent abortion (3+ clinically confirmed spontaneous abortions)
Domestic Violence risks to pregnancy
- Spontaneous abortion
- Preterm birth
- Low birth weight
Recurrent Abortion - Definition, Risk Factors (8) and Mangement
Defined as 3+ clinically confirmed spontaneous abortions.
Risk factors include:
- Infection (Mycoplasma, Listeria, Toxoplasma)
- Smoking and Alcohol
- Psychosocial stress - especially domestic violence!
- Medial conditions (e.g. DM, Hypothyroidism, SLE)
- Maternal Age
- Local Factors
> Uterine Abnormalities
> Cervical Incompetence
> Uterine Submucous Fibroids
> Intrauterine Adhesions
- Foetal Factors - significant genetic/chromosomal abnormalities
- Placental factors
Managed by screening for all the risk factors, uterine US, and chromosome testing, as well as Vitamin D levels. Over 50% of cases will be normal.
Estimating Gestational age and Date of Confinement (due date)
Should be done in the first visit, done by either using the date of last menstration (add 9 months and 1 week = 38 weeks) or US to determine crown-rump length in week 6-11 (accurate to within 7 days)
Indications for genetic screening (9)
Should be offered to all, however there are some indications for testing:
1) Maternal age >38
2) Previous child affected by genetic disorder or mental retardation
3) Previous child who died in neonatal period
4) Multiple foetal losses
5) Abnormal serum marker results
6) Consanguinity
7) Maternal/Paternal conditions/carrier status predisposing the foetus to congenital abnormality/genetic disorder
8) A current pregnancy that has been exposed to teratogens (e.g. antiepileptics)
9) A foetus with abnormal US findings.
10) Women/Couples in difficult life situations where they won’t cope with a disabled child
Most common chromosomal abnormalities (3)
- Sex chromosomal aneuploidies (e.g. Turner’s, Kleinfelter)
- Balanced robertsonian translocations
- Autosomal trisomies (e.g. Tri-21)
Incidence of Down Syndrome vs Age, and main mechanism
<35 = 1/800 35-39 = 1/300 40-45 = 1/80
Most from meiotic nondisjunction (95%)
Fragile X Syndrome Pathophysiology
X-linked disorder that is the second most common cause of developmental delay after Down’s Syndrome. Caused by CGG triplet repeat in the Fragile X mental retardation 1 gene (FMR1), leading to inhibited expression of FMR protein, required for neural development.
First and Second Trimester Screening (5 and 3)
First trimester screening looks at:
- Maternal age
- Foetal nucial translucency (US) = between 10-14 weeks
- Maternal serum β-hCG
- Pregnancy associated plasma protein A (PAPP-A)
- US nasal bone assessment
= down syndrome detection rate of 93%
Second trimester screening is a serum triple screen:
- α-fetoprotein (AFP) –> helps detect neural tube defects, false positive in multiple gestation, foetal demise, or inaccurate gestational age.
- Maternal serum β-hCG
- Unconjugated estratriol (UE3) - at 16-20 weeks
Time of maximum haemodilution
Week 28 - need Hb to compare with first antenatal visit
SF-height measurement
Used to assess foetal growth, between week 20 and 34 - correlates closely with gestational age.
Measured from pubic symphysis to top of the fundus, BLADDER MUST BE EMPTIED. Foetus should be in longitudinal lie, and there cannot be multiple gestations or any other uteral masses (e.g. fibroid)
Foetal heart rate measurement and normal value
110-160 bpm
Doppler US can be used from week 12.
Pinard’s stethoscope can be used in most from week 16, all by week 22. Can help confirm lie of the foetus.
Leopold’s Manouvers, 6 characteristics and method
Start at week 36, helps determine a few characteristics:
- Situs = longitudinal vs transverse?
- Presentation = cephalic/breech/shoulder?
- Position = 1st (back to left) or 2nd (back to right)
- Altitude/Station = how far the leading part has descended
- Habitus = Foetal head in relation to body (deflexed/flexed)
- Engagement = foetal head is descended and locked in the pelvis
Involves 4 manouvers:
1) Hands on top, determine presentation (breech or cephalic?)
2) Lateral palpation - position? Lie?
3) Single handed palpation of presenting part - presentation? Station/engagement? (i.e. ballottable?)
4) From behind, similar to first except away from fundus - presentation? Confirm ballot.
Indications for antenatal OGTT testing (5)
- Age >38
- Type 1 or 2 diabetes in family history
- BMI > 27
- Gestational diabetes in previous pregnancy
- Immigrants from Indian subcontinent or North Africa
Period of organogenesis
weeks 4-10
Role of routine US in antenatal visit (when and why?)
Performed in week 17-19 (visit 2) - referred in visit 1.
The following is checked:
- Length of gestation/due date estimation
- Number of offspring
- Placental position
- Foetal anatomy
Biophysical Profile Testing - 3 components
Used to assess foetal wellbeing, especially indicated in higher risk pregnancies with:
- Intrauterine Growth Restriction
- Diabetes Mellitus
Consists of:
- Maternal assessment –> 10 kicks per hour is normal
- Non-stress testing –> measuring for rises in heart rate every time the baby moves
- Ultrasound assessment –> several components, including measuring amniotic fluid problems (oligohydramnios/polyhydramnios), foetal breathing and stretching movements (30 breaths/3 movements every 10 mins is normal), and doppler assessment of umbilical artery vascular resistance.
Definition of normal labour
Normal labour is defined as progressive cervical effacement and dilation as a result of regular uterine contractions, occurring at least every 3 minutes, and lasting 30-60 seconds each.
Closure of the fontanelles
Posterior fontanelle - 6-8 weeks of life
Anterior fontanelle - 18-24 months of life
Foetal head dimensions (6)
From top:
- Biparietal diameter: 9.5cm
- Bitemporal diameter: 8cm
From side:
- Suboccipitobregmatic (if flexed presentation, from base of skull to ant. fontanelle) - 9.5cm
- Occipitofrontal (if anteflexed presentation, from occipital bone to glabella) - 11cm
- Supraoccipitomental (if brow presentation, from parietal bone to chin) - 13.5cm
- Submentobregmatic (if face presentation, from jaw to ant. fontanelle) - 9.5cm
Pelvis dimensions (5)
AP lengths
- Inlet = 11cm
- Middle = 12cm
- Outlet = 13.5cm
Transverse lengths
- Inlet = 13.5cm
- Outlet = 11cm
Shapes of pelvis (4)
Gynecoid - Found in 50%
- Round inlet
- Curved sacrum
- Straight sides
- Spaceous pubic arch
- Average size spines
- PROMOTES OCCIPUT ANTERIOR
Android - Found in 30%
- Triangular inlet
- Straight sacrum
- Converging sides
- Narrow arch
- Prominent spines
- PROMOTES OCCIPUT POSTERIOR
Arthropod - Found in 20%
- Oval inlet (larger AP)
- Posteriorly inclined sacrum
- Straight sides
- Narrow arch, curved outwards
- Prominent spines (because of diameter)
- PROMOTES OCCIPUT POSTERIOR
Platypelloid - Found in 3%
- Oval inlet (larger transverse)
- Flat sacrum
- Straight sides
- Wide arch
- Large distance between spines (because of diameter)
- PROMOTES TRANSVERSE ENGAGEMENT
Synclitic engagement definition
When the biparietal diameter of the foetal head is parallel to the pelvic plane (when the head lines up nicely with the pelvic plane)
Asynclitic engagement may help reduce the diameter in some situations.
Indications for clinical pelvimetry (2)
1) Clinical evidence/obstetric history suggestive of pelvic abnormality
2) History of pelvic trauma
Lightening
2+ weeks before labour, the baby’s head drops snugly into the pelvic canal.
Induction vs Augmentation of labour
Induction = starting labour artificially Augmentation = stimulating labour artificially after it started naturally.
Cervical ripening
Occurs before labour, often including effacement. Softening of the cervix as a result of prostaglandins and enzyme action
Indications for Induction (3 and 7)
MATERNAL INDICATIONS
> Diabetes Mellitus
> Pre-eclampsia
> Heart Disease
FOETOPLACENTAL INDICATIONS > Prolonged pregnancy > 42 weeks > IUGR > Abnormal foetal testing > Rh Incompatibility > Foetal abnormality > Premature membrane rupture > Chorioamnionitis
Absolute and Relative Contraindications for Induction (1 and 7)
ABSOLUTE
> Contracted pelvis
RELATIVE > Previous uterine surgery > Classic caesarian > Transected uterus (e.g. myomectomy) > Overdistended uterus > Premature baby with immature lungs > Abnormal presentation > Acute foetal distress
Bishop Score
Used to assess likelihood of successful induction.
Uses four cervical indicators and the station of the foetal head.
High score is between 9 and 13.
Induction process (6 pre-induction steps and 5 principles)
There are several things to consider before starting induction:
> Cervical ripening –> promote using PGE2 applied vaginally
> Assess likelihood of successful induction with Bishop score
> Draw blood and perform Rh screen, as well as type and Hb.
> Ensure patient is on continuous Cardiotocography (CTG)
> Check urine for protein/glucose
> Know Hep B status of the mother
Oxytocin infusion is given, keeping in mind several principles
> Give oxytocin IV, to allow fast discontinuation
> Infusion to be “piggybacked” onto saline IV
> Best infused with an infusion pump
> Should not exceed 72 hours
> Reduce dosage if adequate labour established, to avoid complications