History of present pregnancy

The date of the first day of the last menstrual period (or LMP) provides the clinician with an idea of how advanced the current pregnancy is, i.e. period of gestation. However, this information is often inaccurate as many women do not record the days on which they menstruate, unless the date of the period is associated with a significant life event or the woman has been actively trying to conceive. Hence, in addition to LMP, an ultrasound scan in the first or early second trimester should be used to date the pregnancy and to confirm the gestational age.

Menstrual history should also include the duration of the menstrual cycle as ovulation occurs on the 14th day before menstruation. The time interval between menstruation and ovulation (the proliferative phase of the menstrual cycle) may vary substantially, whereas, the post-ovulatory phase (secretory phase) is fairly constant (12–14 days).

The length of the menstrual cycle refers to the time interval between the first day of the period and the first day of the subsequent period. This may vary from 21 to 35 days in normal women, but menstruation usually occurs every 28 days.

It is important to note the method of contraception prior to conception, as hormonal contraception may be associated with a delay in ovulation in the first cycle after discontinuation. The age of onset of menstruation (the menarche) may be relevant in teenage pregnancies to determine the onset of fertility.

The estimated date of delivery (EDD) can be calculated from the first day of the last menstrual period by adding 9 months and 7 days to this date. However, to apply this Naegele’s rule, the first day of the menstrual period should be accurate and the woman should have had regular 28-day menstrual cycles (Fig. 6.1). The average duration of human gestation is 269 days from the date of conception. Therefore, in a woman with a 28-day cycle, this is 283 days from the first day of the last menstrual period (14 days are added for the period between menstruation and conception). In a 28-day cycle, the estimated date of delivery can be calculated by subtracting 3 months from the first day of the LMP and adding on 7 days (or alternatively, adding 9 months and 7 days). It is important to appreciate that only 40% of women will deliver within 5 days of the EDD and about two-thirds of women deliver within 10 days of EDD. The calculation of EDD based on a woman’s LMP is therefore, at best, a guide to a woman as to the date around which her delivery is likely to occur.

If a woman’s normal menstrual cycle is less than 28 days or is greater than 28 days, then an appropriate number of days should be subtracted from or added to the estimated date of delivery. For example, if the normal cycle is 35 days, 7 days should be added to the estimated date of delivery.

Previous obstetric history

The term ‘gravidity’ refers to the number of times a woman has been pregnant, irrespective of the outcome of the pregnancy, i.e. termination, miscarriage or ectopic pregnancy. A primigravida is a woman who is pregnant for the first time and a multigravida is a woman who has been pregnant on two or more occasions.

This term ‘gravidity’ must be distinguished from the term ‘parity’, which describes the number of live-born children and stillbirths a woman has delivered after 24 weeks or with a birth weight of 500 g. Thus, a primipara is a woman who has given birth to one infant after 24 weeks.

A multiparous woman is one who has given birth to two or more infants, whereas, a nulliparous woman has not given birth after 24 weeks. The term ‘grand multipara’ has been used to describe a woman who has given birth to five or more infants.

Thus, a pregnant woman who has given birth to three viable singleton pregnancies and has also had two miscarriages would be described as gravida 5 para 3: multigravid multiparous woman.

A parturient is a woman in labour and a puerpera is a woman who has given birth to a child during the preceding 42 days.

A record should be made of all previous pregnancies, including previous miscarriages, and the duration of gestation in each pregnancy. In particular, it is important to note any previous antenatal complications, details of induction of labour, the duration of labour, the presentation and the method of delivery as well as the birth weight and sex of each infant.

The condition of each infant at birth and the need for care in a special care baby unit should be noted. Similarly, details of complications during labour as well as puerperium such as postpartum haemorrhage, infections of the genital tract and urinary tract, deep vein thrombosis (DVT) and perineal trauma should be enquired. It is vital to appreciate that these complications may have a recurrence risk and also may influence the management of subsequent pregnancies, e.g. history of DVT requires thromboprophylaxis during the antenatal as well as postnatal periods.

Family history

Most women will be aware of any significant family history of the common genetically based diseases and it is not necessary to list all the possibilities to the mother as it may increase her anxiety. A general enquiry as to whether there are any known inherited conditions in the family will be sufficient, unless one partner (or both) is adopted and not aware of their family history.

Detailed and relevant information obtained with regard to demographics (e.g. maternal age, increased BMI), past obstetric, medical and surgical (e.g. laparotomy, caesarean section, myomectomy) history and family history will help perform appropriate tests as well to make a care plan.

General and systemic examination

At the initial visit to the clinic, i.e. the booking visit, a complete physical examination should be performed to identify any physical problems that may be relevant to the antenatal care.

Height and weight are recorded at the first and all subsequent visits and this will help calculation of Body Mass Index (BMI = weight in kg/height in m²).

   Measuring blood pressure in pregnancy

Blood pressure is recorded with the patient supine and in the left lateral supine position to avoid compression of the inferior vena cava by the gravid uterus (Fig. 6.2). If blood pressure is to be recorded in the sitting position, then it should be recorded in the same position for all visits and on the same arm. The effect of posture on blood pressure has been noted in Chapter 3. Vena caval compression in late pregnancy may cause symptoms of syncope and nausea and this is associated with postural hypotension, the condition being known as the supine hypotensive syndrome. If this is not recognized for a prolonged period, fetal compromise may occur secondary to a reduction in uteroplacental circulation.

Although in the past the diastolic pressure has always been taken as Korotkoff fourth sound, where the sound begins to fade, it is now agreed that where the fifth sound, i.e. the point at which the sound disappears, is clear, this should be used as representing the diastolic pressure. If the point at which the sound disappears cannot be identified because it continues towards zero, then the fourth sound should be used.

Heart and lungs

A careful examination of the heart should be made to identify any cardiac murmurs. Benign ‘flow murmurs’ due to the hyperdynamic circulation associated with normal pregnancy are common and are of no significance. These are generally soft systolic bruits heard over the apex of the heart, and occasionally a mammary souffle is heard, arising from the internal mammary vessels and audible in the second intercostal spaces. This will disappear with pressure from the stethoscope (Fig. 6.3).

The presence of all other murmurs should be investigated by a cardiologist, as the early identification of any valvular pathology has implications for the management of the pregnancy, labour and the puerperium.

Examination of the respiratory system involves assessment of the rate of respiration and the use of any accessory muscles of respiration. Gross lung pathology may adversely affect maternal and fetal outcome and should therefore be identified as early in the pregnancy as possible.

Head and neck

Many women develop a brownish pigmentation called chloasma over the forehead and cheeks, particularly where there is a frequent exposure to sunlight (Fig. 6.4). The pigmentation fades after puerperium.

The colour of the mucosal surfaces and the conjunctivae should be examined for pallor, as anaemia is a common complication of pregnancy. The general state of dental hygiene should also be noted, as pregnancy is often associated with hypertrophic gingivitis and dental referral may be needed.

Some degree of thyroid enlargement commonly occurs in pregnancy, but unless it is associated with other signs of thyroid disease it can generally be ignored.

Breasts

The breasts show characteristic signs during pregnancy, which include enlargement in size with increased vascularity, the development of Montgomery’s tubercles and increased pigmentation of the areolae of the nipples (Fig. 6.5). Although routine breast examination is not indicated, it is important to ask about inversion of nipples as this may give rise to difficulties during suckling, and to look for any pathology such as breast cysts or solid nodules in women who complain of any breast symptoms.

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.

Abdomen

Examination of the abdomen commonly shows the presence of stretch marks or striae gravidarum (Fig. 6.6). The scars are initially purplish in colour and appear in the lines of stress in the skin. These scars may also extend on to the thighs and buttocks and on to the breasts. In subsequent pregnancies, the scars adopt a silvery-white appearance. The linea alba often becomes pigmented and is then known as the linea nigra. This pigmentation often persists after the first pregnancy.

Hepatosplenomegaly should be excluded as well as any evidence of renal enlargement. The uterus does not become palpable as an abdominal organ until 12 weeks gestation.

Limbs and skeletal changes

The legs should be examined for oedema and for varicose veins. They should also be examined for any evidence of shortening of the lower limbs, as this may give problems with gait as the abdomen expands.

In addition, posture also changes in pregnancy as the fetus grows and the maternal abdomen expands, with a tendency to develop some kyphosis and, in particular, to develop an increased lumbar lordosis as the upper part of the trunk is thrown backwards to compensate for the weight of the developing fetus (Fig. 6.7). This often results in the development of backache and sometimes gives rise to sciatic pain.

Pelvic examination

Routine pelvic examination to confirm pregnancy and gestation at booking is not indicated in settings where an ultrasound scan is freely available. If a routine cervical smear is due at the time of booking, this can usually be deferred until after the puerperium, as interpretation of cervical cytology is more difficult in pregnancy. Clinical assessment of the size and shape of the pelvis may be useful in specific circumstances such as a previous fractured pelvis, but not in routine practice. Hence, it is generally no longer carried out as part of the routine antenatal examinations.

A speculum examination in early pregnancy is indicated in the assessment of bleeding (see Chapter 18). Pelvic examination in later pregnancy is indicated for cervical assessment (see Chapter 11), the diagnosis of labour and to confirm ruptured membranes (see Chapter 11). Digital vaginal examination is contraindicated in later pregnancy in cases of antepartum haemorrhage until placenta praevia can be excluded.

The role of vaginal examination in normal labour is discussed in Chapter 12.

The technique of pelvic examination in early pregnancy is the same as that for the non-pregnant woman and is described in Chapter 15.

The vulva should be examined to exclude any abnormal lesions and to assess the perineum in relation to any damage sustained in previous pregnancies. Varicosities of the vulva are common and may become worse during pregnancy.

The vaginal walls become more rugous in pregnancy as the stratified squamous epithelium thickens with an increase in the glycogen content of the epithelial cells.

There is also a marked increase in the vascularity of the paravaginal tissues so that the appearance of the vaginal walls becomes purplish-red. There is an increase in vaginal secretions, with increased vaginal transudation, increased shedding of epithelial cells and some contribution from enhanced production of cervical mucus.

The cervix becomes softened and shows signs of increased vascularity. Enlargement of the cervix is associated with an increase in vascularity as well as oedema of the connective tissues and cellular hyperplasia and hypertrophy. The glandular content of the endocervix increases to occupy half the substance of the cervix and produces a thick plug of viscid cervical mucus that occludes the cervical os (Fig. 6.8).

Assessment of the bony pelvis

Routine antenatal clinical or radiological pelvimetry has not been shown to be of value in predicting the outcome of labour. However, it is important to assess the pelvis and fetus for possible disproportion when managing cases of delayed progress in labour. Clinical pelvimetry may be of value where there has been previous trauma or abnormal development of the bony pelvis. Precise information about the various dimensions could be obtained by imaging.

The bony pelvis consists of the sacrum, the coccyx and two innominate bones. The pelvic area above the iliopectineal line is known as the false pelvis and the area below the pelvic brim is the true pelvis. The latter is the important section in relation to childbearing and parturition. Thus, the wall of the true pelvis is formed by the sacrum posteriorly, the ischial bones and the sacrosciatic notches and ligaments laterally, and anteriorly by the pubic rami, the obturator fossae and membranes, the ascending rami of the ischial bones and the pubic rami (Fig. 6.9).

Clinical pelvimetry involves assessment of the pelvic inlet (sacral promontory), mid-cavity (pelvic side walls including the ischial spines, the interspinous diameter and the hollow of the sacrum) and the pelvic outlet (subpubic angle and the intertuberous diameter).

In a normal female or gynaecoid pelvis, because the sacrum is evenly curved, maximum space for the fetal head is provided in the pelvic mid-cavity. The sacrum should feel evenly curved.

If the sacrum feels flat, then the pelvis may contract towards the pelvic outlet, as in the android or male-like pelvis, and may lead to impaction of the fetal head as it descends through the pelvis.

The planes of the Pelvis

The shape and the dimensions of the true pelvis are best understood by consideration of the four planes of the pelvis.

Plane of the pelvic inlet

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. The plane is almost circular in the normal gynaecoid pelvis but is slightly larger transversely than anteroposteriorly.

The true conjugate or anteroposterior diameter of the pelvic inlet is the distance between the midpoint of the sacral promontory and the superior border of the pubic symphysis anteriorly (Fig. 6.10). The diameter measures approximately 11 cm. The shortest distance and the one of greatest clinical significance is the obstetric conjugate diameter. This is the distance between the midpoint of the sacral promontory and the nearest point on the posterior surface of the pubic symphysis.

It is not possible to measure either of these diameters by clinical examination; the only diameter at the pelvic inlet that is amenable to clinical assessment is the distance from the inferior margin of the pubic symphysis to the midpoint of the sacral promontory. This is known as the diagonal conjugate diameter and is approximately 1.5 cm greater than the obstetric diameter. In practical terms it is not usually possible to reach the sacral promontory on clinical examination, and the highest point that can be palpated is the second or third piece of the sacrum. If the sacral promontory is easily palpable, the pelvic inlet is contracted (Fig. 6.11A).

Plane of greatest pelvic dimensions

The plane of greatest pelvic dimensions has little clinical significance and has an anteroposterior and transverse diameter of approximately 12.7 cm. The anteroposterior diameter extends from the midpoint of the posterior aspect of the pubic symphysis to the junction of the second and third pieces of the sacrum. The transverse diameter passes laterally through the middle of the acetabuli.

The only indication of the shape of the pelvis at this level is the curvature of the sacrum and the shape of the sacrosciatic notch, which should subtend an angle of 90°. This normally allows the admission of two fingers along the sacrospinous ligaments, which extend from the ischial spines to the lateral aspects of the second and third pieces of the sacrum.

Plane of least pelvic dimensions

The plane of least pelvic dimensions represents the level at which impaction of the fetal head is most likely to occur. The anteroposterior diameter extends from the inferior margin of the pubic symphysis and transects the line drawn between the ischial spines. Both the transverse (interspinous) and the anteroposterior diameters can be assessed clinically and the interspinous diameter is the narrowest space in the pelvis (10 cm). The ischial spines should be palpated to see if they are prominent and also to make an estimate of the interspinous diameter (Fig. 6.11B).

Obstetrical examination at subsequent routine visits

At all subsequent antenatal visits, the blood pressure should be recorded and the urine tested for protein. It is good practice to record maternal weight at each visit, especially in clinical settings where recourse to ultrasound scan for assessment of fetal growth is not freely available. Maternal weight should increase by an average of approximately 0.5 kg/week after the 18th week of gestation.

Rapid and excessive weight gain is nearly always associated with excessive fluid retention and static weight or weight loss may indicate the failure of normal fetal growth. Excessive weight gain is often associated with signs of oedema and this is most readily apparent in the face, the hands, where it may become difficult to remove rings, on the anterior abdominal wall and over the lower legs and ankles. ‘Non-dependent’ oedema over the sacral pad is rare in pregnancy and, if present, causes such as pre-eclampsia should be excluded.

Measurement of symphysial–fundal height

Direct measurement of the girth or the symphysial–fundal height provides a more reliable method of assessing fetal growth and gestational age.

Measurement of symphysial–fundal height

The ulnar border of the left hand is placed on the uterine fundus. The distance between the uterine fundus and the top of the pubic symphysis is measured in cm. To minimize observer bias, the distance is measured from the fundus to the superior edge of the symphysis pubis with the side of the tape measure with the cm measures facing downwards. The tape measure is then turned over to show the distance in cm. The mean fundal height measures approximately 20 cm at 20 weeks and increases by 1 cm/week so that at 36 weeks the fundal height will be 36 cm (Fig 6.12).

Using two standard deviations from the mean, it is possible to describe the 10th and 90th centile values. The sensitivity of this method for the detection of small for gestational age babies varies from 20% to 70% in different studies. Serial measurements by the same person plotted on customized growth charts are more likely to detect growth restricted babies. The accuracy is considerably reduced as a random observation after 36 weeks gestation. The predictive value is also lower for large-for-dates infants. However, the technique is simple and easily applicable and is particularly useful where other more precise techniques are not available.

Measurement of abdominal girth

Measurement of girth provides another method of assessment. The measurement of girth is made at the level of the maternal umbilicus. Assuming that the average non-pregnant girth is 60 cm, no significant increase will occur until 24 weeks gestation. Thereafter the girth should increase by 2.5 cm weekly so that at full term the girth will be 100 cm.

If the non-pregnant girth is greater or smaller than 60 cm, then an appropriate allowance must be made. Thus, a woman with a 65 cm girth would have a measurement of 95 cm at 36 weeks gestation.

Lie

The term ‘lie’ describes the relationship of the long axis of the fetus to the long axis of the uterus (Fig. 6.14). Facing the feet of the mother, the examiner’s left hand is placed along the left side of the maternal abdomen and the right hand on the right lateral aspect of the uterus. Systematic palpation towards the midline with the left and then the right hand will reveal either the firm resistance of the fetal back or the irregular features of the fetal limbs.

If the lie is longitudinal, the head or breech will be palpable over or in the pelvic inlet. If the lie is oblique, the long axis of the fetus lies at an angle of 45° to the long axis of the uterus and the presenting part will be palpable in the iliac fossa. In a transverse lie, the fetus lies at right angles to the mother and the poles of the fetus are palpable in the flanks.

Having ascertained the lie and the location of the fetal back, it is now important to feel for the head and breech by firm pressure with alternate hands. The head is hard, round and discrete. It can be ‘bounced’ between the examining hands and is described as being ‘ballotable’. The buttocks are softer and more diffuse and the breech is not ballotable. The head should be sought in the lower abdomen or in the uterine fundus. Facing the mother’s feet, firm pressure is applied over the presenting part. If the head is presenting, note is made as to whether it is easily palpable or whether it is necessary to apply deep pressure.

The normal attitude of the fetus is one of flexion (Fig. 6.15) but on occasions, as with the ‘flying fetus’, it may exhibit an attitude of extension.

Presentation

In a longitudinal lie, the presenting part may be the head (cephalic) or the breech (podalic). In a transverse lie, the presenting part is the shoulder.

Depending on the degree of flexion or deflexion, various parts of the head will present to the pelvic inlet. Where the head is well flexed, the presentation is the vertex, i.e. the area that lies between the anterior and posterior fontanelles. If the head is completely extended, the face presents to the pelvic inlet (face presentation) and if it lies between these two attitudes, the brow presents (brow presentation). The brow is the area between the base of the nose and the anterior fontanelle. The diameter of presentation for the vertex is the suboccipitobregmatic diameter (Table 6.1, Fig. 6.16). If the head is deflexed, the occipitofrontal diameter presents. With a brow presentation, the verticomental diameter presents to the pelvic inlet. Presentation and position can be accurately determined only by vaginal examination when the cervix has dilated and the suture lines and fontanelles can be palpated. This situation only really pertains when the mother is well established in labour.

Position

The position of the fetus is a description of the relationship of the denominator to the inlet of the maternal pelvis. It must not be confused with the presentation, although it provides a further description of the relationship of the presenting part to the maternal pelvis and is of particular importance during parturition. The denominators for the various presentations are as follows:

Thus, in a vertex presentation, six different positions are described (Fig. 6.17).

Viewed from below the pelvis, these include right and left occipitotransverse positions as well as left and right anterior and posterior positions. Except in the advanced second stage, it is very rare for the head to be identified in a direct anterior or posterior position.

With a face presentation, the prefix mento- is included and with a breech presentation the prefix is sacro-. No such description is given to a brow presentation, as there is no mechanism of vaginal delivery unless the presentation is corrected.

The position can be determined from abdominal palpation by palpating the anterior shoulder of the fetus. If this is near the midline and easily palpable, the position is anterior. If it is not easily palpable and the limbs are prominent, the position is probably posterior.

However, the position of the presenting part can be most accurately determined by palpating the suture lines and fontanelles or the breech presentation through the dilated cervix once labour has started.

The degree of flexion of the head can also be determined. On abdominal palpation, a deflexed or extended head tends to feel large and the nuchal groove between the occiput and the fetal back is easily identified.

Station and engagement

The station of the head is described in fifths above the pelvic brim (Fig. 6.18). The head is engaged when the greatest transverse diameter (the biparietal diameter) has passed through the inlet of the true pelvis. The head that is engaged is usually fixed and only two-fifths palpable. It is usually difficult to feel abdominally.

Where it is difficult to locate the head, this may either be because the head is under the maternal rib cage, as with a breech presentation, or because it is a case of anencephaly.

Under these circumstances, a vaginal examination should be performed, as the leading part of the engaged head will be palpable at the level of the ischial spines.

Auscultation

Auscultation of the fetal heart rate is a routine part of the obstetric examination. It is now standard practice to use a hand-held Doppler ultrasound device that will produce an electronic signal to enable the heartbeat to be recognized and counted, but should be confirmed with a Pinard fetal stethoscope (Fig. 6.19). The fetal heart sounds are best heard in late pregnancy below the level of the umbilicus over the anterior fetal shoulder (approximately half way between the umbilicus and the anterior superior iliac spine) or in the midline where there is a posterior position. With a breech presentation the sound is best heard at the level of the umbilicus. The rate and rhythm of the heart beat should be recorded.