Self-assessment: Answers

What is the most appropriate description of the arterial supply of the pelvis?

B is correct. The internal iliac artery arises at the level of the lumbosacral articulation and passes over the pelvic brim, continuing downward on the posterolateral wall of the cavity of the true pelvis. The anterior division provides the superior, middle and inferior vesical arteries that provide the blood supply for the bladder. The uterine artery initially runs downward in the subperitoneal fat under the inferior attachment of the broad ligament. The uterine artery crosses over the ureter shortly before that structure enters the bladder approximately 1.5–2 cm from the lateral fornix of the vagina. The ovarian arteries descend behind the peritoneum on the surface of the corresponding psoas muscle until they reach the brim of the pelvis.

The vagina:

A is correct. The vagina is a tube of smooth muscle lined by non-cornified squamous epithelium. Anteriorly, it is intimately related to the trigone of the urinary bladder and the urethra. Posteriorly, the lower third is separated from the anal canal by the perineal body, the middle third is related to the rectum and the upper third to the rectouterine pouch (pouch of Douglas). The pH of the vagina in the sexually mature non-pregnant female is between 4.0 and 5.0, which has an important antibacterial function in reducing the risk of pelvic infection.

Uterus and its supporting structures:

A is correct. The anterior ligament is a fascial condensation which, with the adjacent peritoneal uterovesical fold, extends from the anterior aspect of the cervix across the superior surface of the bladder to the peritoneal peritoneum of the anterior abdominal wall. It has a weak supporting role. Likewise, the broad ligament plays only a minor supportive role. Posteriorly, the uterosacral ligaments play a major role in supporting the uterus and the vaginal vault, and these ligaments and their peritoneal covering form the lateral boundaries of the rectouterine pouch (of Douglas). In pregnancy, the isthmus of the uterus enlarges to form the lower segment of the uterus, which in labour becomes a part of the birth canal but does not contribute greatly to the expulsion of the fetus. (The incidence of uterine retroversion is about 10%.)

The ovary:

D is correct. The ovary lies on the posterior surface of the broad ligament in close proximity to the external iliac vessels and the ureter on the lateral pelvic wall. It is attached to the pelvic brim by the suspensory ligament of the ovary. The surface of the ovary is covered by a cuboidal or low columnar type of germinal epithelium. The blood supply is derived from the ovarian artery, which arises directly from the aorta. The follicles are found in both the cortex and medulla of the organ.

Uterus:

B is correct. The blood supply to the uterus comes largely from the uterine artery, but branches of this anastomose with branches of the ovarian vessels in the upper part of the broad ligament, assuring adequate collateral supply to the uterus even following internal iliac ligation. Lymphatic drainage follows the blood vessels. Uterine pain is mediated through sympathetic afferent nerves passing up to T11–T12 and L1–L2. The pudendal nerve (somatic nerve) supplies the vulva and pelvic floor.

What is the most appropriate statement relating to spermatozoa?

D is correct. The sperm head fuses with the oocyte plasma membrane, and the sperm head and midpiece are indeed engulfed into the oocyte by phagocytosis. The body contains a coiled helix of mitochondria that provides the ‘powerhouse’ for sperm motility. The tail consists of a central core of two longitudinal fibres surrounded by nine pairs of fibres that terminate at various points until a single ovoid filament remains. These contractile fibres propel the spermatozoa. During their passage through the Fallopian tubes, the sperm undergo the final stage in maturation (capacitation), which enables penetration of the zona pellucida. Seminal plasma has a high concentration of fructose, which is the major source of energy for the spermatozoa. Under favourable circumstances, sperm migrate at a rate of 6 mm/min. This is much faster than could be explained by the motility of the sperm and must therefore also be dependent on active support within the uterine cavity.

Normal follicular growth:

B is correct. In a normal ovulatory menstrual cycle, one follicle is selected to become the dominant follicle on day 5–6 of the cycle (B is therefore correct); however, up to 10 show obvious but lesser growth than the dominant follicle (A is therefore incorrect). The dominant follicle grows by 2 mm per day thereafter (C is therefore incorrect) and ruptures at about 2 cm in diameter (D is therefore incorrect), and this ruptured follicle becomes the corpus luteum after release of the oocyte (E is therefore incorrect).

Meiosis:

C is correct. The 7 million germ cells produced during fetal life are produced by mitosis, not meiosis (A is therefore incorrect). The first meiotic division commences in utero in the fetus but ceases in prophase. It does not recommence its division until the luteinizing hormone surge occurs in the particular menstrual cycle, and this first meiotic division is completed just prior to fertilization of the oocyte by the sperm (B is therefore incorrect). The attachment of the sperm results in the commencement of the second meiotic division (C is therefore correct). The crossover process between adjacent copies of the same chromosome occurs during prophase of meiosis I, not after meiosis I has been completed (D is therefore incorrect). The long delay between the cessation of prophase I in fetal life and the time when it recommences in the cycle concerned (which can be 40–45 years later) is the reason for the increased incidence of chromosomal abnormalities associated with advanced maternal age (E is therefore incorrect).

Regarding the process of fertilization in the human female:

A is correct. The female gametes only contain an X chromosome and therefore cannot determine the sex of the resulting fetus. This is determined by the male gamete, which will contain either an X or Y chromosome (B is therefore incorrect). Twin pregnancies occur due to division of the embryo (identical or monochorionic twin pregnancy) or if two separate oocytes are fertilized by two separate sperm (a dichorionic twin pregnancy; therefore C is incorrect). The exact time during which the oocyte can be fertilized after ovulation is uncertain, but it is believed fertilization does not occur if this time interval is in excess of 36 hours (D is therefore incorrect). Sperm capacitation to facilitate fertilization generally occurs within the genital tract of the woman (E is therefore incorrect).

Implantation:

C is correct. Implantation generally occurs 5–6 days after ovulation and fertilization (A is therefore incorrect), at which time the embryo is at the blastocyst stage (B is therefore incorrect). Human chorionic gonadotropin (hCG) is produced soon after the implantation process commences (C is therefore correct), and then the plasma levels double every 48 hours if the pregnancy is progressing normally. The endometrium must be secretory in type to allow implantation (D is therefore incorrect) and is then converted to the appearance of decidua. Implantation will not occur if the endometrium is proliferative in type so a pregnancy will not result. Implantation and hCG production can occur even where the embryo is very abnormal, under which circumstances the period occurs at the expected time and the woman concerned never knows she was actually pregnant in that cycle (E is therefore incorrect). A urinary pregnancy test performed 2–3 days after the period commenced will be negative.

What is the most appropriate statement regarding immunology in pregnancy?

A is correct . Only two types of feto-placental tissue come into direct contact with maternal tissues: the villous and extra-villous trophoblast (EVT), and there are effectively no systemic maternal T- or B-cell responses to trophoblast cells in humans. The villous trophoblast, which is bathed by maternal blood, never expresses human leucocyte antigen (HLA) class I or class II molecules. EVT, which is directly in contact with endometrial/decidual tissues, does not express the major T-cell ligands, HLA-A or HLA-B, but does express the HLA class I trophoblast-specific HLA-G, which is strongly immunosuppressive, along with HLA-C and HLA-E. The main type of decidual lymphocytes is the uterine natural killer (NK) cells. The thymus shows some reversible involution during pregnancy, apparently caused by the progesterone-driven exodus of lymphocytes from the thymic cortex, and the Th1:Th2 cytokine ratio shifts towards Th2.

Regarding the rise in cardiac output:

D is correct. The rise in cardiac output is seen from early pregnancy. The increase in cardiac output is brought about by increase in the stroke volume and the heart rate. It is associated with a fall in the afterload. The heart is already strained due to the need to pump an extra 40% of blood volume, and in those with heart disease it can tip the balance and cause heart failure, especially if they are anaemic or if they contract an infection. The pulmonary vasculature in a mother is able to accommodate the increased blood flow without causing pulmonary hypertension.

Considering respiratory function in pregnancy:

D is correct. Progesterone sensitizes the medulla oblongata and not the adrenal medulla to CO ₂ . This causes some over-breathing, which reduces the CO ₂ level that allows the fetus to offload its CO ₂ to the maternal side. Not the maternal P _a O ₂ but the oxygen-carrying capacity of blood increases by 18%. There is an increase in maternal 2,3-DPG that shifts the maternal oxygen dissociation curve to the right, thus facilitating the down-loading of oxygen to the fetus. There is a 40% increase in minute ventilation due to increase in tidal volume from 500 to mL.

Considering renal function in pregnancy:

C is correct. There is an increase in renal size of up to 70% due to an increase in size of the parenchyma in addition to the enlargement of the pelvicalyceal system and the ureter, but the increase is seen from early pregnancy. The ureters increase in size due to the influence of progesterone and increased urinary output, but they are not floppy and have good tone. Because of an increase in blood volume there is a 50% increase in glomerular filtration rate (GFR) that activates the renin–angiotensin system. About 900 and not 1800 mmol of sodium are retained during pregnancy. Because of ureteric dilatation and reflux of urine due to lack of sphincteric action at the point entry of the ureter into the bladder and higher incidence of urinary stasis, there is higher incidence of urinary tract infection in pregnancy.

In relation to endocrine function in pregnancy:

A is correct. Insulin resistance develops with progress of pregnancy due to the change in the hormonal milieu. There is a significant increase in human placental lactogen after 28 weeks as a result of which some women develop gestational diabetes. Due to increased glomerular filtration rate, more glucose is presented to the kidneys, and in some mothers the quantity of glucose exposed for absorption exceeds the tubular maximal absorption capacity and hence presents as ‘renal’ glycosuria without a high blood glucose level. Because of increased metabolism, the thyroid increases in size. The gut absorbs more calcium but more is also lost in the urine and in areas of dietary deficiency, so calcium supplementation becomes necessary. Skin pigmentation is caused by an increase in melanocyte-secreting hormone.

In early placental development:

D is correct. The villi have an inner cytotrophoblast and an outer syncytiotrophoblast that invade the endometrium and myometrial layers. Decidual cells provide the initial nutrition for the invading trophoblasts. The spiral arterioles are invaded by the trophoblasts making large lacunae that are full of maternal blood, and the tertiary villi bathe in these lacunae to accomplish the respiratory, nutrition and excretory functions. Chorion frondosum forms the placenta. Chorion laevae is the layer surrounding the membranes, and it fuses with the uterine cavity.

Regarding the umbilical cord:

C is correct. The umbilical cord has two arteries and one vein. The fetus pumps the blood through these arteries to the placenta to get more oxygen and excrete the carbon dioxide, and hence arterial blood has less oxygen compared with the vein. One in 200 babies has only one artery and one vein, and they grow normally and live birth is achieved. Cord arterial pressure is between 60 and 70 mmHg. The vessels are surrounded by a hydrophilic mucopolysaccharide known as Wharton’s jelly.

Placental transfer:

A is correct. Simple diffusion is according to the concentration gradients, and this facilitates transfer of oxygen and carbon dioxide in the right direction for the fetus. Glucose is transferred according to the gradient, but it needs energy, i.e. facilitated diffusion. Active transport needs energy for transport and to drive the substances against the gradient, and hence there could be cases where the concentration may be already higher in the fetal blood. This process occurs with amino acids and water-soluble vitamins. Higher-molecular-weight substrates are transferred by pinocytosis.

Placental function:

E is correct. The placenta has multiple functions. It helps with gas exchange and is an important organ for transferring nutrition to the fetus and excreting waste products from the fetus. It produces a number of hormones – initially human chorionic gonadotrophin and later oestrogens and progesterones, which are all essential for maintenance of pregnancy. But it is a poor barrier against infections; thus the fetus is affected by malaria, syphilis, HIV, cytomegalovirus (CMV) and toxoplasmosis.

Amniotic fluid:

A is correct. Polyhydramnios may suggest fetal anomaly such as neural tube defects, anencephaly, gut atresia and several other known pathologies. The amniotic fluid volume increases rapidly in parallel with fetal growth and gestational age up to a maximum volume of around 1000 mL at 38 weeks. Postural deformities are one of the complications of long-standing severe oligohydramnios. A major problem with this situation is pulmonary hypoplasia. Adequate fluid is needed to push the alveoli and bronchioles to expand; if not, it results in lung hypoplasia. Most cases of intrauterine growth restriction would be associated with reduced amniotic fluid due to less urine production caused by less renal perfusion. Amnio-infusion may abolish the variable decelerations, but trials have shown no improvement in clinical outcome, and hence it is not a standard procedure.

Perinatal mortality:

C is correct. Perinatal mortality rate describes the number of stillbirths and early neonatal deaths per 1000 total births (live births and stillbirths). This gives a picture of maternal health and the standard of care provided to mothers and their newborn babies. By improving socio-economic conditions, the quality of obstetric and neonatal care and an active screening programme for common congenital abnormalities, perinatal mortality rates can be significantly improved. The World Health Organization has two targets for assessing progress in improving maternal health (Millennium Development Goal [MDG] 5). These are reducing the maternal mortality ratio by 75% between 1990 and 2015 and achieving universal access to reproductive health by 2015.

Regarding stillbirths:

E is correct. Stillbirths are the number of stillbirths per 1000 total births. Until 2011, the Centre for Maternal and Child Enquiries has published annual perinatal reports for the UK. The report showed a significant reduction in both stillbirth rates and early neonatal deaths. Stillbirth rates indicate the quality of antenatal care and screening programmes and are the largest contributors to perinatal mortality. Most stillbirths occur antenatally. The traditionally used systems such as the Wigglesworth and the Aberdeen (Obstetric) classifications consistently reported up to two-thirds of stillbirths as being from unexplained causes. The ReCoDe (Relevant Condition at Death) system, which classifies the relevant condition present at the time of death, was developed in the UK. By using this system, the most common cause of stillbirth was fetal growth restriction (43%), and only 15.2% remained unexplained. The sub-Saharan regions of central Africa have the highest stillbirth rates.

Regarding neonatal deaths:

B is correct. Birth weight is no doubt an indication of maternal health and nutrition. Low birth weight, although not a direct cause of neonatal death, is an important association. Neonatal tetanus remains a common cause of neonatal death in settings where lack of hygiene and inadequate cord care are prevalent, as many women are not immunized against tetanus. Prematurity remains a significant contributor to perinatal mortality rates in developing countries, and improving maternal health and obstetric care is a more important step to improving the outcome than providing more neonatal intensive care units. In the UK, the neonatal classification used by the Confidential Enquiry into Maternal Deaths (CMACE) looked at the primary cause and associated factors for neonatal deaths. In the past, nearly half of the neonatal deaths were due to immaturity, but the new classification restricted extreme prematurity to only cases below 22 weeks’ gestation, resulting in only 9.3% of neonatal deaths.

Regarding the description of maternal deaths:

A is correct. Direct maternal deaths are defined as those resulting from conditions or complications or their management that are unique to pregnancy, occurring during the antenatal, intrapartum or postpartum periods. Coincidental (fortuitous) deaths occur from unrelated causes which happen to occur in pregnancy or the puerperium. Definitions of maternal death can vary across the regions and between countries. As the UK has the advantage of accurate denominator data, including both live births and stillbirths, it has defined its maternal mortality rate as the number of direct and indirect deaths per 100,000 maternities as a more accurate denominator to indicate the number of women at risk. Maternities are defined as the number of pregnancies that result in a live birth at any gestation or stillbirths occurring at or after 24 completed weeks of gestation and are required to be notified by law. Improving the socio-economic status of women, coupled with improved maternal health and antenatal care, is key to the improvement of maternal mortality rates.

Maternal mortality:

D is correct. In the 2006–2008 UK Confidential Enquiry into Maternal Deaths Report, the leading cause of direct deaths was sepsis, particularly from group A streptococcus. This infection can occur at any time during the antenatal or postpartum period, and the onset can be insidious and non-specific. Cardiac diseases remained the leading cause of indirect deaths. The reduction in the number of deaths from venous thromboembolism is due mainly to improved screening and thromboprophylaxis guidelines adopted by all maternity units in the UK. However, it remains an important and avoidable cause of death.

Physiological changes in pregnancy:

E is correct . Breast cancer during pregnancy is reportedly associated with rapid progression and poor prognosis. Hence, any complaint of a ‘lump’ in the breast should prompt a detailed breast examination. Many women develop a reddish-brownish pigmentation called chloasma over the cheeks, which is normal and needs no investigation in the absence of any other symptoms or signs. There is a physiological reduction in Hb concentration due to a relative haemodilution (plasma expansion is greater than red cell expansion). The pelvic shape remains unchanged in itself – it is what is from birth. The plane of the pelvic inlet or pelvic brim is bounded posteriorly by the sacral promontory, laterally by the iliopectineal lines and anteriorly by the superior pubic rami and upper margin of the pubic symphysis.

In eliciting an obstetric history:

E is correct. Past obstetric history is pivotal to managing the index pregnancy, e.g. past history of diabetes, hypertensive or psychiatric illness would help us to plan management better. Many women do not remember the last menstrual period (LMP) accurately, and when facilities permit, the gestation is assessed by ultrasound in the first trimester and estimated date of delivery (EDD) is calculated based on the early scan. The post-ovulatory period is fairly constant and is about 14 days whether the cycle is long or short. Ultrasound for dating can be + or − 3 weeks if it is based on third-trimester scans, while it is + or − 1 week if it is based on a first-trimester scan. Hormonal contraception may delay the first ovulatory cycle after discontinuation of the method.

Regarding symptoms of pregnancy:

E is correct. Nausea and vomiting can start within 2 weeks of the missed period, and it is believed to be secondary to the rise, at least partly, of human chorionic gonadotrophin (hCG). Severe and persistent vomiting leading to maternal dehydration, ketonuria and electrolyte imbalance is termed hyperemesis gravidarum and is typical in the first trimester only . The frequency of micturition is due to the increased urine production, which is due to an increased glomerular filtration rate following 40% expansion of the blood volume in addition to the pressure on the bladder by the gravid uterus. This pressure is relieved after 12 weeks when the uterus becomes an intra-abdominal organ – hence the frequency lessens. Plasma osmolality reduces with advancing gestation due to increased intravascular volume and reduced plasma proteins. There is increased diuresis after water loading when the woman is sitting in an upright position, perhaps due to increased perfusion.

During pregnancy:

C is correct. Blood pressure (BP) is recorded when the patient is sitting up or lying at a 45-degree incline and not whilst she is lying on her back because the venous return may be reduced, affecting the cardiac output and the reading. BP should be recorded in the same position during each visit using an appropriate size cuff – obese women would need a larger cuff. If inferior venocaval compression is prolonged, it is likely to affect the cardiac output of the mother and hence the uterine circulation, which could compromise the baby. Current recommendation is to consider the Korotkoff’s fifth sound, and if the point at which the sound disappears cannot be identified, then use the Korotkoff’s fourth sound. The flow murmurs are due to the hyper-dynamic circulation and are generally of no significance unless associated with symptoms or other worrying clinical features, where they should be differentiated from any murmur due to cardiac pathology.

In pelvic examination during pregnancy:

B is correct. With the availability of first-trimester scanning, it is not essential to perform a routine pelvic examination. When there is painless bleeding in late pregnancy, placenta praevia should be excluded. Digital vaginal examination in cases of placenta praevia may cause torrential haemorrhage and require an emergency caesarean section; hence, it is contraindicated. Radiological examination of the pelvis is of little value in predicting labour outcome, as labour is a dynamic process with changes in dimensions occurring with flexion of the baby’s head, moulding and pelvic ‘give’. The gynaecoid pelvis is ‘roomy’ at all levels of the pelvis to allow cephalic descent. The diameter of the pelvic inlet is usually longer in the transverse diameter than the anteroposterior (AP) diameter.

Regarding antenatal screening for infection:

B is correct. Screening for hepatitis B is routinely carried out. Hepatitis B is easily transmitted to the fetus and then the newborn whilst it traverses the birth canal. If the mother has hepatitis B antigens, further testing is required to confirm if they are positive for surface (s) antigens or core (e) antigens. Those who are positive for core antigens are considered to have active viruses and may have a high transmission rate of up to 85% to the fetus. In most countries newborns are given gamma globulins and the active vaccine if e positive and only the vaccine if they are s positive. If the infection is transmitted, there is a high possibility of liver cirrhosis followed by hepatocellular cancer, hence the need to actively immunize the newborn. No routine screening is done for cytomegalovirus (CMV), as re-infection is not uncommon and no preventive action can be taken based on the test. General advice should be given to avoid child nurseries where children have coughs, colds and influenza and may harbour CMV infection that is easily transmitted. Syphilis is uncommon, but if detected it is eminently treatable to avoid infection of the fetus and its sequelae. Checking the husband/partner and contact tracing are important. Rubella infection causes major congenital malformations in 25–50% if the mother is infected in the first trimester of pregnancy. If the mother is not immune, she should be immunized postpartum. HIV/AIDS screening is not universal, but it is advisable to make it a routine screening. If found positive, antiretroviral therapy, elective caesarean delivery and avoidance of breast-feeding have reduced the incidence of vertical transmission from 45% to less than 2%.

Group B streptococcus:

C is correct. Group B streptococcus is a gram-positive bacterium and is a commensal organism found in the nose, oropharynx, nasopharynx, anal canal and vagina. Group B streptococcal colonization of the genitourinary tract is associated with higher incidence of pre-term labour and pre-labour rupture of membranes. Screening is not routine in all countries. In the UK screening is not performed, but should there be a high-risk history, suitable precautions are taken, especially intrapartum penicillin therapy if the mother had streptococcal colonization in the vaginal or rectal swab or growth in urine culture.

Gestational diabetes:

E is correct. Gestational diabetes predisposes to macrosomic babies, and those who had higher-birth-weight babies in the previous pregnancy are more prone to gestational diabetes. The cut-off value of when to consider the baby to be macrosomic, i.e. >4 or 4.5 kg, varies with the population studied. Maternal body mass index (BMI) >35 has a known association with gestational diabetes mellitus in pregnancy. Gestational diabetes in previous pregnancy identifies those who are likely to develop early-onset type 2 diabetes in their life, and they also indicate a higher chance of getting gestational diabetes in subsequent pregnancies. Older mothers >35 years of age are more prone to gestational diabetes and not younger mothers.

Extra folic acid supplementation:

E is correct. Folic acid is well known to reduce the overall incidence of congenital malformations. Folic acid facilitates cell division and is an important vitamin in any growth or reparative process. Extra folic acid supplementation (5 mg per day) reduces neural tube defects, and hence it is important to take prior to and in early pregnancy in mothers who had a previous child with neural tube defects. Mothers who have epilepsy, especially those who are on anti-epileptic medication, have a higher chance of having children with neural tube defects, and they should be advised on higher-dose folic acid supplementation. This also applies to mothers with diabetes and those with a high body mass index (BMI), e.g. >35. Down’s syndrome is a chromosomal problem, commonly trisomy 21, and the incidence cannot be reduced by taking extra folic acid.

Regarding advice in pregnancy:

D is correct. Moderate exercise for recreation, including swimming, is harmless and is encouraged. Strenuous exercise and competitive sports with active movements are contraindicated. Anti-D Ig is not routinely administered after complete spontaneous miscarriage under 12 weeks’ gestation in the absence of surgical evacuation. There is controversy about minimal alcohol consumption and its effects on the fetus. Moderate alcohol consumption may be harmful to the fetus, and severe alcohol consumption is associated with fetal alcohol syndrome, which is associated with microcephaly and mental retardation. Smoking is harmful to the pregnancy and is well known to be associated with intrauterine growth restriction. Paracetamol appears to be safe in pregnancy, though no drug is proven to be completely safe. Non-steroidal anti-inflammatory drugs taken in significant amounts in the third trimester may cause oligohydramnios and premature closure of the ductus arteriosus.