Pregnancy

Pregnancy Trimester

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FIRST TRIMESTER (FIRST 12 WEEKS)

SUBJECTIVE SYMPTOMS

Amenorrhea during the reproductive period in an otherwise healthy individual having previous normal periods, is likely due to pregnancy unless proved otherwise. However, cyclic bleeding may occur up to 12 weeks of pregnancy, until the decidual space is obliterated by the fusion of decidua vera with decidua capsularis. Such bleeding is usually scanty, lasting for a shorter duration than her usual and roughly corresponds with the date of the expected period. This is termed as placental sign. This  type of bleeding should not be confused with the commonly met pathological bleeding, i.e. threatened abortion. Pregnancy, however, may occur in women who are previously amenorrheic—during lactation and puberty.

Morning sickness (Nausea and vomiting) is inconsistently present in about 70% cases, more often in the first pregnancy than in the subsequent one. It usually appears soon following the missed period and rarely lasts beyond 16 weeks. Its intensity varies from nausea on rising from the bed to loss of appetite or even vomiting. But it usually does not affect the health status of the mother.

Frequency of micturition is quite troublesome symptom during 8–12th week of pregnancy. It is due to 

(1) resting of the bulky uterus on the fundus of the bladder because of exaggerated anteverted position of  the uterus,

(2) congestion of the bladder mucosa.

(3) change in maternal osmoregulation causing increased thirst and polyuria. As the uterus straightens up after 12th week, the symptom disappears.

Breast discomfort in the form of feeling of fullness and ‘pricking sensation’ is evident as early as 6–8th week specially in primigravidae.

Fatigue is a frequent symptom which may occur early in pregnancy.

OBJECTIVE SIGNS: 

Breast changes~ are valuable only in primigravidae, as in multiparae, the breasts are enlarged and often contain milk for years. The breast changes are evident between 6 and 8 weeks. There is enlargement with vascular engorgement evidenced by the delicate veins visible under the skin. The nipple and the areola (primary) become more pigmented specially in dark women. Montgomery’s tubercles are prominent. Thick yellowish secretion (colostrum) can be expressed as early as 12th week.

Per abdomen:- Uterus remains a pelvic organ until 12th week, it may be just felt per abdomen as a suprapubic bulge.

Pelvic changes:-The pelvic changes are diverse and appear at different periods. Collectively, these may be informative in arriving at a diagnosis of pregnancy.

Jacquemier’s:- or Chadwick’s sign: It is the dusky hue of the vestibule and anterior vaginal wall visible at about 8th week of pregnancy. The discoloration is due to local vascular congestion.

Vaginal sign:- (a) Apart from the bluish discoloration of the anterior vaginal wall

(b) T e walls become softened and

(c) Copious non-irritating mucoid discharge appears at  6th week 

(d) There is increased pulsation, felt through the lateral fornices at 8th week called Osiander’s sign.

Cervical signs:- (a) Cervix becomes soft as early as 6th week (Goodell’s sign), a little earlier in multiparae. The pregnant cervix feels like the lips of the mouth, while in the non-pregnant state, like that of tip of the nose.

(b) On speculum examination, the bluish discoloration of the cervix is visible. It is due to increased vascularity.

Uterine signs:- (a) Size, shape and consistency — The uterus is enlarged to the size of hen’s egg at 6th week, size of a cricket ball at 8th week and size of a fetal head by 12th week. The pyriform shape of the non-pregnant uterus becomes globular by 12 weeks. There may be asymmetrical enlargement of the uterus if there is lateral implantation. This is called Piskacek’s sign where one half is more f rm than the other half. As pregnancy advances, symmetry is restored. The pregnant uterus feels soft and elastic.

(b) Hegar’s sign: It is present in two-thirds of cases. It can be demonstrated between 6 and 10 weeks, a little earlier in multiparae. This sign is based on the fact that: 

(i) upper part of the body of the uterus is enlarged by the growing fetus.

(ii) lower part of the body is empty and extremely soft and.(iii) the cervix is comparatively firm. Because of variation in consistency, on bimanual examination (two fingers in the anterior fornix and the abdominal fingers behind the uterus), the abdominal and vaginal fingers seem to appose below the body of the uterus. Examination must be gentle to avoid the risk of abortion.

(c) Palmer’s sign: Regular and rhythmic uterine contraction can be elicited during bimanual examination as early as 4–8 weeks. Palmer in 1949, first described it and it is a valuable sign when elicited.

To elicit the test, the uterus is cupped between the internal fingers and the external fingers for about 2–3 minutes. During contraction, the uterus becomes firm and well defined but during relaxation, becomes soft and ill defined. While the contraction phase lasts for about 30 seconds, with increasing duration of pregnancy, the relaxation phase increases. After 10th week, the relaxation phase is so much increased that the test is difficult to perform.

IMMUNOLOGICAL TESTS FOR DIAGNOSIS OF PREGNANCY

Principle: Pregnancy tests depend on detection of the antigen (hCG) present in the maternal urine or serum with antibody either polyclonal or monoclonal available commercially.

Tests used:

A. Immunoassays without radioisotopes

Agglutination inhibition tests — Using latex (LAI). The materials for these tests are supplied in kits containing all the reagents needed to do a test.

Principle of agglutination inhibition tests: One drop of urine is mixed with one drop of a solution that contains hCG antibody. If hCG is not present in the urine sample (e.g. the woman is not pregnant), the antibody remains free. Now one drop of another solution that contains latex particles coated with hCG is added. Agglutination of the latex particles can be observed easily this time. Therefore, the pregnancy test is negative if there is agglutination.On the other hand, if hCG were present in the urine sample (e.g. woman was pregnant), it would bind the available antibody. There would be no further agglutination when the solution containing hCG coated latex particles was added. Therefore, pregnancy test is positive if there is no agglutination (schematic presentation above).

Direct agglutination test (hCG direct test) — Latex particles coated with anti-hCG monoclonal antibodies are mixed with urine. An agglutination reaction indicates a positive result when the urine sample contains hCG. Absence of agglutination (urine without hCG) indicates a negative one. The sensitivity is 0.2 IU hCG/mL.

Enzyme-linked immunosorbent assay (ELISA) — It is based on one monoclonal antibody that binds the hCG in urine and serum. A second antibody that is linked with enzyme alkaline phosphatase is used to ‘sandwich’ the bound hCG. It is detected by color change after binding. This is more sensitive and specific. ELISA can detect hCG in serum up to 1–2 mIU/mL and as early as 5 days before the first missed period.

Fluoroimmunoassay (FIA)— It is a highly precise sandwich assay. It uses a second antibody tagged with a fluorescent label. The fluorescence emitted is proportional to the amount of hCG. It can detect hCG as low as 1 mIU/mL. FIA takes 2–3 hours. It is used to detect hCG and for follow up hCG concentrations.

B. Immunoassays with radioisotopes

Radioimmunoassay (RIA) — It using I125 ido hCG antibodies. It is more sensitive and can detect β subunit of hCG up to 0.002 IU/mL in the serum. It can detect pregnancy as early as 8–9 days after ovulation (day of blastocyst implantation). Radio receptor assay gives highest sensitivity of 0.001 IU/mL in the serum. RIAs are quantitative, so can be used for determining the doubling time of hCG (ectopic pregnancy monitoring). RIAs require 3–4 hours to perform.

Immunoradiometric assay (IRMA) — It uses sandwich principle to detect whole hCG molecule. IRMAs use I125 labeled hCG and require only 30 minutes. It can detect hCG as low as 0.05 mIU/mL.

Selection of time: Diagnosis of pregnancy by detecting hCG in maternal serum or urine can be made by 8 to 11 days after conception. The test is not reliable after 12 weeks. Collection of urine: The patient is advised to collect the first voided urine in the morning in a clean container (not to wash with soap). Kits to perform the test at home are also available.

Other uses of pregnancy tests: Apart from diagnosis of uterine pregnancy, the tests are employed in the diagnosis of ectopic pregnancy, to monitor pregnancy following in vitro fertilization and embryo transfer and to follow up cases of hydatidiform mole and choriocarcinoma. Test accuracy ranges from 98.6 – 99%. Non-pregnant level is below 1 mIU/mL.

Limitations: Test accuracy is affected due to presence of (i) hemoglobin (ii) albumin (iii) LH and (iv) immunological diseases.

Advantages: They are advantageous over the biological methods because of their speed, simplicity, accuracy and less cost. Biological tests were based on the classic discovery of Aschheim and Zondek in 1927. All these tests are of historical interest.

ULTRASONOGRAPHY: Intradecidual gestational sac (GS) is identified as early as 29 to 35 days of gestation.

Fetal viability and gestational age is deter- mined by detecting the following structures by

transvaginal ultrasonography. Gestational sac and yolk sac by 5 menstrual weeks; Fetal pole and cardiac activity — 6 weeks; Embryonic movements by 7 weeks. Fetal gestational age is best determined by measuring the CRL between 7 and 12 weeks (variation ± 5 days). Doppler effect of ultrasound can pick up the fetal heart rate reliably by 10th week. The instrument is small, handy and cheap. The gestational sac (true) must be differentiated from pseudogestational sac.

 

SECOND TRIMESTER (13–28 WEEKS)

SYMPTOMS: The subjective symptoms — such as nausea, vomiting and frequency of micturition usually subside, while amenorrhea continues. The new features that appear are:

“Quickening” (feeling of life) denotes the perception of active fetal movements by the women.- It is usually felt about the 18th week, about 2 weeks earlier in multiparae. Its appearance is an useful guide to calculate the expected date of delivery with reasonable accuracy (see later in the chapter). 

Progressive enlargement:- of the lower abdomen by the growing uterus.

GENERAL EXAMINATION

Chloasma: Pigmentation over the forehead and cheek may appear at about 24th week.

Breast changes: (a) Breasts are more enlarged with prominent veins under the skin.

(b) Secondary areola specially demarcated in primigravidae, usually appears at about 20th week.

(c) Montgomery’s tubercles are prominent and extend to the secondary areola.

(d) Colostrum becomes thick and yellowish by 16th week.

(e) Variable degree of striae may be visible with advancing weeks.

ABDOMINAL EXAMINATION 

Inspection: (1) Linear pigmented zone (linea nigra) extending from the symphysis pubis to ensiform cartilage may be visible as early as 20th week.

(2) Striae (both pink and white) of varying degree are visible in the lower abdomen, more towards the flanks.

Palpation: Fundal heightis increased with progressive enlargement of the uterus. Approximate duration of pregnancy can be ascertained by noting the height of the. uterus in relation to different levels in the abdomen. The following formula is an useful guide for the purpose. The height of the uterus is midway between the symphysis pubis and umbilicus at 16th week; at the level of umbilicus at 24th week and at the junction of the lower third and upper two-thirds of the distance between the umbilicus and ensiform cartilage at 28th week.

The uterus feels soft and elastic and becomes ovoid in shape.

Braxton-Hicks contractions are evident, the features of which have been mentioned.

Palpation of fetal parts can be felt distinctly by 20th week. The f ndings are of value not only to diagnose pregnancy but also to identify the presentation and position of the fetus in later weeks.

Active fetal movements can be felt at intervals by placing the hand over the uterus as early as 20th week. It not only gives positive evidence of pregnancy but of a live fetus. The intensity varies from a faint f utter in early months to stronger movements in later months.

External ballottement is usually elicited as early as 20th week when the fetus is relatively smaller than the volume of the amniotic fluid. It is dif cult to elicit in obese patients and in cases with scanty liquor amnii. It is best elicited in breech presentation with the head at the fundus.

Auscultation 

Fetal heart sound (FHS) is the most conclusive clinical sign of pregnancy. With an ordinary stethoscope, it can be detected between 18–20 weeks. The sounds resemble the tick of a watch under a pillow. Its location varies with the position of the fetus. The rate varies from 110–160 beats per minute. Two other sounds are confused with fetal heart sounds. Those are:

Uterine souffle is a soft blowing and systolic murmur heard low down at the sides of the uterus, best on the left side. The sound is synchronous with the maternal pulse and is due to increase in blood f ow through the dilated uterine vessels. It can be heard in big uterine fibroid.

Funic or fetal souffle is due to rush of blood through the umbilical arteries. It is a soft, blowing murmur synchronous with the fetal heart sounds.

VAGINAL EXAMINATION

The bluish discoloration of the vulva, vagina and cervix is much more evident, so also softening of the cervix.

Internal ballottement can be elicited between 16–28th week. The fetus is too small before 16th week and too large to displace after 28th week. However, the test may not be elicited in cases with scanty liquor amnii, or when the fetus is transversely placed.

INVESTIGATIONS (Imaging Studies)

Sonography:Routine sonography at 18–20 weeks permits a detailed survey of fetal anatomy, placental localization and the integrity of the cervical canal. Gestational age is determined by measuring the biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL). It is most accurate when done between 12 and 20 weeks (variation ± 8 days). BPD is measured at the level of the thalami and cavum septum pellucidum. BPD is measured from outer edge of the skull to the inner edge of the opposite side.

Fetal organ anatomy is surveyed to detect any malformation. Fetal viability is determined by real- time ultrasound. Absence of fetal cardiac motion confirms fetal death.

Magnetic Resonance Imaging (MRI): MRI can be used for fetal anatomy survey, biometry and evaluation of complex malformations.

Radiologic evidence of fetal skeletal shadow may be visible as early as 16th week.

 

LAST TRIMESTER (29-40 WEEKS)

SYMPTOMS: 

(1) Amenorrhea persists.

(2) Enlargement of the abdomen is progressive which produces some mechanical discomfort to the patient such as palpitation or dyspnea following exertion.

(3) Lightening — At about 38th week, specially in primigravidae, a sense of relief of the pressure symptoms is obtained due to engagement of the presenting part.

(4) Frequency of micturition reappears.

(5) Fetal movements are more pronounced.

SIGNS:

Cutaneous changes are more prominent with increased pigmentation and striae.

Uterine shape is changed from cylindrical to spherical beyond 36th week.

Fundal height:- The distance between the umbilicus and the ensiform cartilage is divided into three equal parts. The fundal height corresponds to the junction of the upper and middle third at 32 weeks, up to the level of ensiform cartilage at 36th week and it comes down to 32 week level at 40th week because of engagement of the presenting part. To determine whether the height of the uterus corresponds to 32 weeks or 40 weeks, engagement of the head should be tested. If the head is f oating, it is of 32 weeks pregnancy and if the head is engaged, it is of 40 weeks pregnancy. 

Symphysis fundal height (SFH):- The upper border of the fundus is located by the ulnar border of the left hand and this point is marked. The distance between the upper border of the symphysis pubis up to the marked point is measured by a tape in centimeter. After 24 weeks, the SFH measured in cm corresponds to the number of weeks up to 36 weeks. A variation of ± 2 cm is accepted as normal. Variation beyond the normal range needs further evaluation.

Braxton-Hicks contractions are more evident.

Fetal movements are easily felt.

Palpation of the fetal parts and their identif cation become much easier. Lie, presentation and position of the fetus are determined.

FHS is heard distinctly in areas corresponding to the presentation and position of the fetus. FHS may not be audible in cases of maternal obesity, polyhydramnios, occipitoposterior position and certainly in IUD.

Sonography — gestational age estimation by BPD, HC, AC and FL is less accurate (variation ± 3 weeks). Fetal growth assessment can be made provided accurate dating scan has been done in first or second trimester. 

Fetal AC at the level of the umbilical vein is used to assess gestational age and fetal growth prof le (IUGR or macrosomia). Placental anatomy: Location (fundus or previa), thickness (placentomegaly in diabetes) or other abnormalities. are noted. 

Other information Fetal life, number, presentation and organ anatomy as done in the first and second trimester are surveyed again.