Symptoms may have rendered an earlier scan necessary but under normal circumstances the first scan is offered at  12 weeks. There is no evidence that sensible limited scanning harms pregnancies.

This scan can usually achieve adequate results when performed through the abdomen. A full bladder is no longer required for this. This scan will show whether there is a baby and how many. Up to 3% of women do not have a living fetus on this scan particularly if there has previously been vaginal bleeding. The fetus (or fetuses) is measured from head to bottom (crown rump length) with assessment of amniotic fluid and placenta.

Modern equipment permits excellent views and more and more of the detailed structure can be seen on this scan. An important development is the measurement of the skin fold thickness on the back of the neck in conjunction with a hormonal blood test as a predictor of Down syndrome and associated conditions. The result is expressed as a probability as 1 in “X”. Discussion can take place on whether to have chorion villous sampling or amniocentesis based on this result.

• These tests, involving the passage of a sampling needle into the uterus, carry an inherent added risk of miscarriage of about 1% but give a definitive answer to whether the baby is chromosomally normal or not.

The presence of more than one baby provokes surprise and concern. The human female was designed to produce one offspring at a time. The presence of twins or more increases the risks to the fetuses and, less so, to the mother proportionately to the number of fetuses. A critical determinant of these risks is the chorionicity determined on scan.

• The person scanning will observe whether there is a thick or a thin membrane between the twins and whether there is a thickening of the membrane as it is inserted near the placenta. Should the membrane be thin without thickening near the insertion (absent lambda sign) then the twins are monochorionic. This means they are identical, sharing some blood vessels in the placenta, and face the added hazards of twin to twin transfusion syndrome, miscarriage and prematurity.

• More rarely they are in one sac (mono amniotic) facing even more hazards. The extreme manifestation of this lack of full splitting is conjoined twins. Mono chorionic and mono amniotic pregnancies should be assessed by an expert in materno fetal-medicine.

Booking in with a midwife or doctor for pregnancy care takes place around the time of the twelve week scan.

• An extensive history will be recorded
• A basic examination undertaken
• Blood tests will be offered

A haemoglobin test is recommended to measure the strength of the blood. Pregnancies require expansion of the blood volume to support the growing fetus and also to prepare for inevitable blood loss at delivery. A general vitamin and iron preparation taken by mouth is useful. The blood group and blood antibody status of the mother is checked. Women of European and North America have a 10-15% chance, less in other groups, of being Rhesus antigen negative. When their partner is Rhesus positive, as they usually are, it is important to know that they are, and remain, antibody negative.

Blood will be tested in later pregnancy and an injection of immunoglobulin (Anti D) may be given.

A blood test for syphylis is also offered: undetected and untreated syphylis can harm the unborn baby.

A blood test for rubella (German Measles) is also offered: most females are immune through previous exposure or immunization. If they are not already immune then immunization is offered after delivery.

Rubella in early pregnancy can harm the unborn baby in a non-immune woman and special tests are required. In woman of Afro Caribbean origin then a blood test is offered to assess sickle cell status and in those of Mediterranean/Asian origin then a test for thalassaemia is important.

In recent years with the increasing importance of Acquired Immune Deficiency Syndrome (AIDS) an HIV (Human Immunodefiency Virus) test has been offered. The implications of this have changed because of evidence that treatment of known cases may improve the outcome for mother and baby. This treatment involves antiviral medicine, caesarean section for delivery and the avoidance of breast feeding.

Apart from threatened miscarriage, urinary infections and the effects of fibroids or cysts the mid part of pregnancy is usually uncomplicated. In centres where skin fold thickness is not available then a hormonal blood test (the triple test) may be offered at 15-18 weeks to assess the probability of Down syndrome. A visit to a doctor or midwife should be made at this time to review the results of all investigations and make plans for the rest of the pregnancy.

Women feel fetal movements (quickening) at 18-20 weeks in the first pregnancy. They are felt sooner in subsequent pregnancies. Initially felt as fluttering they then become quite active as limb movements. A moving baby is a healthy baby.