Stages of pregnancy: Introduction

• Introduction
• What is gestational age?
• What is my due date?
• Why is it important I see my doctor regularly during my pregnancy?
• Pregnancy week by week

Introduction

This series aims to introduce you to the changes taking place inside a pregnant woman’s uterus, some of the changes that pregnant women may experience during pregnancy, and routine doctor appointments. In this series, the developmental age is referred to as the pregnancy age or weeks. 

What is gestational age?

This series is headed by gestational age. Gestational age refers to the number of weeks since the pregnant woman’s last menstrual period (LMP). This differs from the developmental age of the foetus which, depending on the exact time of fertilisation, is approximately 2 weeks less than the gestational age.

What is my due date?

The expected length of gestation in humans is 40 weeks ± 2 weeks. The due date (expected birth date of your baby) is therefore the date 40 weeks after your last menstrual period (LMP). If the date of your last menstrual period is uncertain, an early dating ultrasound (an ultrasound performed early in the pregnancy) is performed to calculate the age of the foetus, and from this information, the expected date of delivery. During the early stages of embryo development (i.e. 6 Weeks Pregnant), there are several key external features that can be used to accurately determine the age of the embryo developing in your womb.

Why is it important I see my doctor regularly during my pregnancy?

Antenatal care refers to the series of doctors’ appointments and/or interventions that a woman receives from healthcare services during her pregnancy. While the majority of care takes place during the pregnancy, antenatal care also includes those appointments and/or interventions related to the pregnancy that occur before and after the pregnancy – i.e. doctors’ appointments related to pregnancy planning and optimising medical conditions/medication before falling pregnant (preconception counselling), and care after the delivery of the baby (postpartum period).

A definition from the 1930s that still stands today is that antenatal care is “the whole art of preventive obstetrics”. Hence antenatal care acts to prevent or identify and treat conditions that may cause harm to the foetus/newborn or the mother. In doing so, it also aims to help women have positive pregnancy and birth experiences.

It is important to attend regular antenatal care so that the best health outcomes for both you and your baby can be achieved. Having an understanding of the changes taking place within your body will help you to understand some of the symptoms that you may experience during your pregnancy and when you should seek help from your doctor.

Pregnancy week by week

For more information, see 1 Week Pregnant: The Last Menstrual Period.

More information

For more information on foetal development and maternal changes during pregnancy, see Stages of Pregnancy.

For more information about pregnancy, including preconception advice, stages of pregnancy, investigations, complications, living with pregnancy and birth, see Pregnancy.

References

1. Moore KL, Persaud TVN. The Developing Human: Clinically Oriented Embryology (7th edition). Philadelphia: Saunders; 2003. [Book]
2. Gibbs RS, Karlan BY, Haney AF, Nygaard IE (eds). Danforth’s Obstetrics and Gynecology (10th edition). Baltimore: Lippincott Williams & Wilkins; 2008. [Book]
3. Schoenwolf GC, Bleyl SB, Brauer PR, Francis-West PH. Larsen’s Human Embryology (4th edition). Philadelphia: Churchill-Livingstone; 2009. [Book]
4. Banta D. Health Evidence Network report: What is the efficacy/effectiveness of antenatal care and the financial and organizational implications? [online]. Copenhagen: World Health Organization; December 2003 [cited 2 August 2010]. Available from: URL link
5. Devenish C. Standards of antenatal care. O&G Magazine. 2009;11(4):22-3. [Full text]