Prenatal screening tests are an important part of any woman’s pregnancy and can provide vital information about your baby’s health before he or she is born as well as that of your own. Screening tests are available to all pregnant women and are aimed at detecting any disorders or abnormalities at the earliest possible chance. They differ from prenatal diagnostic tests in that they require follow-on testing before any solid diagnosis can and will be given.


The time at which you undergo specific screening tests depends on your particular stage of pregnancy, together with your personal health and family history profile. Those placed in high-risk groups for certain disorders may undergo some procedures at earlier stages or via more invasive methods. The routine screening tests offered to pregnant women listed here are not mandatory and an expectant mother can ask to opt out of these and other, screening treatments at her own discretion. You should discuss your options with your midwife or a doctor before making any solid decisions.

Physical Examinations

Weight and height measurements may be taken during the initial midwife appointments. These numbers are only really a cause for concern for significantly underweight and overweight mothers and so are generally only taken once.

Blood pressure is measured at regular intervals during a pregnancy, as it is an important indication of pre-eclampsia, a potentially fatal and often asymptomatic complication that can lead to seizures in the final trimester.

Blood Tests

Blood samples are generally taken throughout a woman’s pregnancy to keep an eye on her iron levels and general state of health.

They can also be used to determine any disorders that a mother may suffer from that may be passed on to her child. These include serious genetic blood disorders such as sickle cell anaemia and thalassaemia as well as infectious diseases such as hepatitis B, syphilis and HIV.

Blood group is also assessed through blood tests, particularly the rhesus D status of the mother. If you are rhesus D negative and your baby is rhesus D positive you may create anti-D antibodies in your bloodstream. Though generally not problematic for your first pregnancy, future pregnancies may be at risk as the mother’s previously prepared immune system attacks. Anti-D treatment options are available to counteract this.

Ultrasound Scans

For most parents, their first scan is a happy experience and a chance to see your baby for the first time. The first ‘early pregnancy scan’ is mainly used to determine your stage of pregnancy whilst assessing the general growth and development of your child. It’s also a chance to hear your baby’s heartbeat for the first time as well as checking out just how many babies you have in there.

At later stages, usually around 18-21 weeks, a mid-pregnancy scan is performed. This is sometimes referred to as a fetal anatomy survey and is a chance to look closer at your baby’s development. It considers the growth of the limbs, counting fingers and toes, and the general development of the vital organs. The position and state of the placenta can also be determined at this stage as well as the sex of the child.

Nuchal Ultrasound Scans

If you are worried about your baby’s risk of Down syndrome, you may be offered a Nuchal scan. This is a type of ultrasound that takes place around 11-13 weeks of your pregnancy and specifically determines the amount of fluid collected around the neck. Babies with Down’s syndrome usually have an increased amount of fluid here at this stage but this is only an indication however and positive results warrant the need for further invasive tests.

Blog post written by Dr. Wendy Snell of  Blossoms Healthcare


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