Written by : Dr.M.D.Mazumdar, MD

Normal pregnancy lasts for 280 days or 40 weeks. 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 is divided into three more or less equal stages, known as trimesters. Each of these trimesters correlate with different stages of fetal development - the first trimester is associated more with development of the fetal organs, the second trimester is associated with growth and enlargement of the developed organs and the third trimester is associated with growth plus physiological maturity. Physiological maturity means that the organs can now function more or less like an adult's- relasing enzymes or hormones etc.

The first trimester lasts from the first day of the last missed perod to the end of 13 weeks.

The second trimester lasts from the beginning of the 14th week to the end of the 27th week.

The third trimester lasts from the beginning of the 28th week to the end of the 40th week of pregnancy.

The expected date of delivery or the expected due date (EDD) is the date when the baby is expected to deliver. It is calculated by counting 9 months plus 7 days from the first day of the last missed period. This calculation s 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.

How Pregnancy Occurs

As we all know, pregnancy occurs when a sperm fuses with an ovum to form a new cell known as the zygote. The zygote divides to form an embryo. The embryo is initially closely attached to the inner uterine lining (the endometrium). At around the 8th week of pregnancy, it remains attached to the uterine wall only by the umbilical cord and is then able to swim freely in the liquor amnii in the pregnancy sac - at this stage it is called a fetus. The term 'fetus' is used right till delivery labor and childbirth. Read More ...

First Trimester

The first trimester is one of active development of the fetal organs from a single fertilized cell - the 'zygote'. The early symptoms of pregnancy like morning sickness, nausea, fatigue, sore breasts gradually appear and become more severe as the trimester advances. The uterus cannot be felt through the abdomen during this trimester. But by the end of the trimester, it can be felt as a bump along the edge of the pubic bone, especially in thin women. Read more ...

Second Trimester

During the second trimester, the fetal organs grow rapidly. It is the most pleasant time during pregnancy - morning sickness gradually decreases and in most women, is over by the 14th week, the earlier fatigue decreases, appetite returns, and the overall feeling of constant ill-health decreases. The pregnancy begins to show through the abdomen. The breasts become larger and the nipples and areola darken with appearance of the secondary areola. Read More...

Third Trimester

The third trimester starts from the end of the 27week and ends with labor and childbirth. This is the time in pregnancy when the fetal weight increases - the organs enlarge and become mature and a layer of fat is deposited under the skin. For the mother, symptoms of backache may appear as the baby becomes heavier. She may need to go the bathroom more frequently since the uterus presses on the bladder. Other symptoms are constipation, leakage of colostrum, Braxton Hicks Contractions etc. Read More ...

Pregnancy Tests

The aim of all pregnancy tests in the blood and the urine is the identification of the Human Chorionic Gonadotrophin (HCG) hormone by the use of special reagents.With the invention of pregnancy home test kits, this identification has become easier and less expensive. HCG is secreted by the human placenta as early as 7 to 10 days after fertilization, that is, at around the time of implantation and becomes detectable in the urine at around the time of the first missed period. Read More ...

Common Words Used in Pregnancy

Some clinical words like embryo, fetus, implantation, lie of the baby are specific to pregnancy. The lie and the presentation of the baby are important when the mother goes into labor.Read More ...

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