Duration of Pregnancy - It is calculated by clinicians as 10 lunar months or 9 calendar months and 7 days or 280 days or 40 weeks calculated from first day of the last menstrual period. This is called menstrual or gestational age.

As fertilization occurs 14 days prior to the expected missed period and in previously normal cycle of 28 days duration, it is about 14 days after the first day of the period. Thus the true gestation period is to be calculated by substracting 14 days from 280 days i.e. 266 days. This is called fertilization or ovulatory age.

SIGN & SYMPROMS OF PREGNANCY
Pregnancy is divided into three trimesters

First trimester (0-12 weeks)
Second trimester (13-28 weeks)
Third trimester/last trimester (29-40 weeks)

First Trimester - Presumptive/subjective symptoms of early months of pregnancy are :

1. Amenorrhea - Cessation of menstruation during the reproductive period in an otherwise healthy individual having previous normal periods is due to pregnancy unless proved otherwise.
   
   
2. Morning sickness - It is present in 50% of cases and is more pronounced in first pregnancy. It appears following the missed period till the end of first trimester. It can be in form of nausea on rising from the bed or vomiting and loss of appetite.
   
   
3. Frequency of micturition (increased frequency of urination) - It is more during 8-12th week and symptoms disappear after the 12th week.
   
   
4. Breast discomfort - Feeding of fullness and pricking sensation is present from 6-8th week.
   
   
5. Easy fatigability is a frequent symptom.

Objective Signs

1. Breast Changes - Breast signs are valuable only in primigravidae (in first pregnancy) changes are evident from 6-8 weeks. There is enlargement of breast and delicate veins visible under the skin.
   
   Nipple and areola became more pigmented especially in dark women. Thick yellowish secretion can be expressed from nipple as early as 12th week.
   
   
2. Pelvic changes - Uterus remains a pelvic organ till 12th week. These changes may help in the diagnosis of pregnancy.
   
   Vaginal Sign - Copious non-irritative mucoid discharge from the vagina.
   Uterine Sign - Pregnant uterus feels soft and elastic and is enlarged in size. Regular and rhythmic uterine contractions can be elicited during bimanual examination by 4th week.
   

Second Trimester
The symptoms of nausea & vomiting and frequency of micturition usually subside. The new features that appears are:

1. Quickening: It denotes the perception of active fetal movement by the women. It is felt about 16-18th week. It can be a useful guide to calculate the expected date of delivery.
   
   
2. Progressive enlargement of the lower abdomen.
   
   
3. Appearance of secondary areola in breast at about 20th week
   
   
4. Chloasma: pigmentation on the forehead and cheek may appear at about 24th week.

Signs
The symptoms of nausea & vomiting and frequency of micturition usually subside. The new features that appears are:

1. Linea nigra - A linear pigmented line appears on abdomen below umbilicus in midline and can be seen from 20th week.
   
   
2. Striae (both pink and white) are visible on the lower abdomen.
   
   
3. Uterus is further enlarged till above the umbilicus and is ovoid in shape.
   
   
4. Imegular spasmodic infrequent and painless contraction can be felt on the uterus - Braxton Hicks contractions.
   
   
5. Active foetal movement can be felt by 20th week.
   
   
6. 5. Foetal heart sounds can be hard with a stethoscope by 18-20 weeks. It is the most conclusive clinical sign of pregnancy.

Third Trimester
Symptoms

1. Amenorrhoea Persists.
   
   
2. Enlargement of the abdomen is progressive which produces mechanical discomfort to the patient such as palpitation or dyspnoea following exertion.
   
   
3. Lightening - At about 38th week a sense of relief of the pressure symptoms is obtained due to descent of the head of the fetus into pelvis.
   
   
4. Frequency of micturition reappears.
   
   
5. Foetal movements are more pronounced.
   
   

Signs

1. Cutaneous changes - Increase in pigmentation and striae.
   
   
2. Uterine shape becomes spherical from cylindrical beyond 36th week.
   
   
3. Braxton Hicks contractions are more evident.
   
   
4. Palpation of the foetal parts become much easier
   
   
5. Foetal heart sound is heard distinctly
   
   
6. Radiology or sonography gives conclusive evidence of pregnancy.
   
   

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