Pregnancy occurs when a male sperm fertilizes a female ovum - the cell thus formed is known as a zygote. The zygote is single celled but as soon as it divides into two cells, it is known as an embryo. The term 'fetus' is used from 8 weeks of pregnancy till childbirth.
The gestational period of a normal pregnancy is 40 weeks or 280 days or 9 months and 7 days. The expected date of delivery (EDD) is calculated based on the length of the menstrual cycle. If the menstrual period is not normal ( a normal menstrual cycle is 4 weeks), then the EDD may be preponed or postponed depending on the length of the menstrual cycle.
A baby who is born after 42 weeks is termed a postmature baby and one who is born before 37 weeks is a preterm baby.
Pregnancy may be complicated or uncomplicated. A very common complication is anemia in pregnancy. Other common complications are ectopic pregnancy, placenta previa, diabetes, pre-eclamptic toxemia (PET) and Rh-ve pregnancy. A twin pregnancy may be normal but complications are also quite common.
The entire duration of pregnancy is divided into three phases, known as trimesters. Each trimester is approximately 13 weeks long. Stages of fetal development and maturation correlete very well with the different trimesters of pregnancy.
First Trimester - This trimester starts from the first day of the last missed perod to the end of 13 weeks. During this time, the baby grows from a single celled zygote to a fetus which can swim freely in the amniotic fluid. At 4 weeks of pregnancy, the baby is about the size of a sesame seed ( Til) but by the end of the 13th week, it is almost the size of an orange.
In the mother, early first trimester is marked by symptoms like nausea and vomiting, loss of appetite, fatigue, excessive sleepiness, acid reflux, constipation and sometimes mild pain and cramps in the lower abdomen. By the end of the first trimester, the uterus can be felt through the abdominal wall just above the pelvic bone.
Second Trimester - The second trimester starts from the end of the 13th week to the end of the 27th week. At the end of the second trimester, the baby is approximately 15 inches long (the size of the long ruler or scale used in the classroom). All the body parts are well developed and the baby can be seen opening and closing its eyes.
For the mother, the second trimester is a period of comfort - the acute symptoms of the first trimester decreases and she can eat and sleep well. The uterus enlarges and by the end of this trimester,the upper border can be felt about one inch above the umbilicus (belly button).
Third Trimester - This trimester lasts from the beginning of the 28th week to the end of the 40th week of pregnancy. The baby's organs continue to mature and the baby increases in length and weight. At 40 weeks, a mature baby is about 20 inches in length from head to buttocks and about 3 kgs in weight in an average indian woman.
The increasing weight of the baby causes symptoms of pressure in the pregnant woman. Pressure on the lungs causes difficulty in breathing, especially while lying down, pressure on the stomach makes it difficult to eat large meals, pressure on the bladder causes frequent desire to pass urine and pressure on the rectum causes constipation.
Expected Date of delivery (EDD) The expected date of delivery or the expected due date (EDD) is the date when the baby is expected to be born. It is calculated by counting 9 months plus 7 days from the first day of the last missed period. This calculation is accurate only if a woman has a regular menstrual cycle of 28 +/- 2 days. If the cycle is longer, the extra days need to be added to the total duration.
For a woman who has an irregular menstrual cycle, an ultrasound in early pregnancy is more accurate.
A pregnancy is a time of great joy and expectation in all couples and they need proper support and advice during this crucial period for a successful pregnancy and to welcome a healthy baby.
Dr. Madhumita Das Mazumdar, MD(O&G)
Senior Consultant Gynecologist,
House No 7, Trinayan Path,
Opp Ascent Academy,Beltola Tiniali
Opp BSNL Office, Lachit Nagar,
Near Bora Service Petrol Pump, Ulubari
Phone - +919954056516