Invasive Prenatal Diagnosis

Introduction
Once a woman has been given a high risk of aneuploidy based on a Down screening, a structural anomaly detected on scan or because of her previous history an obstetrician would normally counsel the women on the options of invasive karyotyping.
This counselling should be based on the risk of aneuploidy, the voluntary nature of the test, the option of no testing, the technique of the proposed test, the procedure-related loss rate and other common complications associated with the test, the timing of the result and the possible management options depending on the result of the test. This decision to balance the potential risk of the loss of an unaffected fetus against that of having an affected child is a very difficult and traumatic one and it is
important that the parents are not rushed into a premature decision.

1. Amniocentesis
Amniocentesis should be performed after 15 weeks when the uterus is an abdominal organ and the proportion of fluid needed to be removed (15–10 ml) is relatively small compared to the overall liquor volume at this gestation (150–250 ml).

Procedure: The procedure is performed under aseptic conditions under continuous ultrasound guidance. Best practice is for the operator to introduce a gauge 22–20 needle percutaneously while he or she is continuously scanning using the free hand. The needle is preferably introduced into a cord free pool of liquor avoiding the placenta. Once in place the inner stylet of the needle is withdrawn and an initial 2 ml of amniotic fluid is withdrawn by an assistant and discarded to avoid maternal contamination. Then a further 15–20 ml is removed using a 10–20 ml syringe.
A few operators use a needle guide attached to the transducer, but this has the disadvantage of being less flexible if the needle needs to be realigned.

There is clearly a learning curve with any invasive procedure. Studies have demonstrated the significance of operator experience in terms of both failed attempts and miscarriage. Amniocentesis is therefore not a routine procedure and it is recommended by the Royal College of Obstetricians
and Gynaecologists (RGOG) that it is only performed by adequately trained individuals with at least 50–100 supervised procedures and 50 procedures per annum to maintain their skills. In general only two needle insertions should be attempted and if these fail then the woman should be referred to a tertiary level fetal medicine unit for repeat attempts.
The miscarriage rate for amniocentesis is generally quoted as 1:100 (1%) .

Common Gynecologic Procedures

1. Bimanual pelvic examination
Two fingers are placed in the vagina and the flat of the opposite hand is placed on the lower abdominal wall. Gentle palpation and manipulation should delineate the position, shape, mobility, tenderness, and size of the uterus and adnexal structures.

Indications: It is a part of routine pelvic exam and part of investigation for gynecologic pathology. Tenderness may be elicited on direct palpation or on movement/ stretching of pelvic structures (i.e. acute salpingitis or pelvic inflammatory disease [PID])

Drawbacks: Difficult to elicit any information on obese patients or uncooperative patients.

2. Cervical conization
It is a surgical procedure that involves excising a cone-shaped sample of tissue that includes the entire cervical transformation zone and a portion of the endocervical canal. The sample is then examined for any signs of malignancy.
Conization can be performed using a knife (cold knife cone), laser excision, and electrocautery (large loop excision of the transformation loop electrosurgical excision procedure.

Indications: It is used for either diagnostic or therapeutic reasons. The test is done when results of a cervical biopsy indicate precancerous cells in the area or cervical cancer. It may also be done if the cervical biopsy has not revealed the cause of an abnormal Pap smear.

Complications: An early complication is excessive bleeding. Infrequent complications include cervical stenosis or incompetence.

Important Definitions Used In Gynecological Practice.

Menarche – first menstrual period.

Menopause – date of final menstrual period. This can only be defined with certainty after a year has elapsed since the final menstrual period. It is also useful to ask about menopausal symptoms and hormone replacement therapy (HRT) use. The classic menopausal symptom is vasomotor flushes, but a myriad of other symptoms can also be experienced.

Perimenopause – the years of transition where irregular cycles occur. For most women, this lasts for 4 years before the final menstrual period occurs.

Menorrhagia – heavy periods. This is one of the commonest reasons that women are referred to gynecology.
You should ask for how long and how often bleeding occurs. The passage of clots and flooding through sanitary protection are signs that the menstrual flow is excessive. It can also be useful to ask about frequency of changing sanitary protection and whether ‘double’ protection is required, that is, having to wear a sanitary towel and tampon at the same time.

Abnormal Bleeding
Postcoital bleeding – bleeding occurring after intercourse.
Intermenstrual bleeding – bleeding between periods.
Postmenopausal bleeding – bleeding more than one year since LMP.

Irregular Bleeding
Primary amenorrhoea – failure to menstruate by age 16.
Secondary amenorrhoea – no menstruation for 6 months after periods are established.
Oligoamenorrhoea – infrequent, erratic periods.

Remember that anovulatory cycles occur at the extremes of menstrual life. It is therefore physiological to have erratic infrequent periods in the first few years after menarche and in the perimenopause.

Hyperemesis gravidarum - A Brief Discussion

Hyperemesis gravidarum: This is defined as persisting vomiting in pregnancy which causes weight loss (>5% of pre-pregnancy weight) and ketosis.

Incidence: It affects 1% of pregnant women.

Risk factors; Risk is increased in

• Very young, 
• primigravida, 
• working outside home, 
• preexisting diabetes, 
• hyperthyroidism, 
• psychiatric illness, 
• family history, 
• those with previous eating disorders and 
• multiple or molar pregnancy 

Clinical Presentation

• Inability to keep food or fluids down; 
• weight loss (2–5 kg)with or without nutritional deficiency, 
• dehydration, 
• hypovolaemia, 
• tachycardia, 
• postural hypotension,
• electrolyte disturbance with hypokalaemia and hyponatraemic shock,
• polyneuritis (B vitamins defeciency), 
• behaviour disorders, 
• liver and renal failure in severe cases.  
• There may be ptyalism (inability to swallow saliva) and spitting.

Workup

Bartholin gland Abscess

Introduction: Bartholin glands are locate on either side of the lower third of the vaginal introitus near the labia minora.
A cyst or abscess may result from an obstructed duct, often secondary to trauma or inflammation. Infection of the cyst is usually with mixed vaginal or fecal flora (Escherichia coli) but may also contain N gonorrhoeae and Chlamydia trachomatis.

Clinical Features: Cysts or abscesses may be asymptomatic or may lead to increasing pain, swelling,
an dyspareunia. A tender, fluctuant cystic mass with surrounding labial edema is easily appreciate on examination.

Differential diagnosis: Differentials should include

• epidermal inclusion cysts and sebaceous cysts of the labia majora, 
• hidradenitis suppurativa, 
• vulvar hematomas, 
• leiomyomas, 
• lipomas, and 
• fibromas.

Ultrasound Screening For Fetal Anomalies

Routine first trimester dating scanning has a number of benefits like
(1) it is more accurate at assessing gestational age than menstrual periods, and therefore reduces the
rates of induction of labour for post-term pregnancies
(2) detects multiple pregnancies early in pregnancy and
(3) can detect some major structural anomalies such as anencephaly.

Nuchal scan or Nuchal translucency (NT) scan: A  more detailed, although limited, anomaly scan is incorporated into a nuchal scan or nuchal translucency (NT) scan which helps in determining the basics such as

• the shape of the fetal skull, 
• presence of nose, hands and feet and 
• presence of stomach and bladder. 

Therefore, instigation of Down’s syndrome screening strategies such as the Combined or Integrated test which involve an NT scan are likely to not only increase the detection of aneuploidy but also major structural anomalies and particularly cardiac defects earlier in gestation.

Routine Second Trimester Ultrasound Screening For Fetal Anomalies 
In the UK and most of the other countries around the world. there is a policy of routine second trimester ultrasound screening for fetal anomalies .
However, detection of fetal anomalies varies considerably depending on the anomaly being screened for as well as the gestation at screening, the skill of the operator and the quality of the equipment used.

The detection of cardiac anomalies is of particular interest. Early prenatal detection of congenital heart disease (CHD) has increased due to advances in ultrasound resolution and the incorporation of at least a 4-chamber cardiac view in the routine anomaly scan.