Testing during Pregnancy

You cross your fingers and wait nervously for the home pregnancy test to do its thing. A few minutes later, you have the answer you’ve been waiting for - and your journey towards motherhood begins.

Some women may have a blood test before they fall pregnant, looking in particular for immunity to Rubella (German Measles). If that test is negative or low, you would be advised to have a vaccine, and then wait for a month before trying for a pregnancy.

At your initial visit, your GP or obstetrician will take your medical history, perform an examination and health check, perform a pap smear if it is due (or overdue!) and estimate when your baby will be due. If the period dates are uncertain, or if you have an irregular cycle, the doctor will ask for an early scan to work out the dates. You will usually have a blood test, to perform the standard antenatal screening tests and sometimes to check the level of pregnancy hormone in your blood. A urine test will also be performed to check for low-grade infection in the bladder.

The initial blood test will check your blood group and antibody screen (to make sure there is no blood group incompatibility between you and the baby). If your blood group is Rhesus negative, you will require extra testing at 26 and 34 weeks, along with injections at that time to minimize the risk of problems for this or future babies. A blood count will check your haemoglobin to test for anaemia, which may require iron or other supplements. Incidentally, we all recommend that women should take pregnancy vitamins before falling pregnant or at least as soon as you find out that you are pregnant, and continue through to the end of the pregnancy and for the period that you breast feed. Your Rubella immunity will be checked, if it hasn’t been confirmed before the pregnancy, along with screening tests for infectious diseases such as Hepatitis B, Hepatitis C, Syphilis and HIV. In some circumstances, we might also check for Iodine or Vitamin D deficiency, thyroid function, and perhaps immunity to Chicken Pox and Whooping Cough.

From this point, assuming you are healthy and have no complicating factors, you should visit your doctor every four weeks until the 26th week of pregnancy. After that, the tempo picks up a little with fortnightly visits until the 36th week. In the ‘home stretch’ you will see your doctor every week. Your doctor will check your blood pressure, feel your abdomen to check the size and position of your baby and check the baby’s heart beat, usually using a Doppler machine. I would point out that it is considered unnecessary to perform a urine test at every visit. It is also unnecessary to weigh women at every visit, unless there are specific concerns about your weight (if you are very big or very small).

Other routine testing which is offered can be split into each of the three trimesters (3 month periods of the pregnancy). Additional tests in the first trimester include the Down’s syndrome screen, performed between 11 and 14 weeks – best performed at about 12 weeks. This will involve an abdominal ultrasound to measure the “nuchal translucency” or the skin fold thickness at the back of the baby’s neck. This is done with a blood test to calculate the risk of a Down’s baby. If this turns out to be in the high risk range (higher than 1 in 300) further assessment of the baby will be discussed with your doctor.

In the second trimester, (18 to 20 weeks) another ultrasound is performed. This will check the baby’s size, the physical appearance of the baby, including the brain, heart, abdominal structures and limbs. Although very minor defects might not be detected even with modern ultrasound scanning, major defects, including Spina Bifida, are reliably picked up at this scan. The position of the placenta is also noted.

In the third trimester, usually between 26 and 28 weeks, we screen for diabetes of pregnancy and repeat the tests for anaemia and any blood group incompatibility (a blood count and antibody screen). The initial diabetes screen involves having a blood test one hour after a sugar drink provided by the lab. If it is high, a more formal two hour fasting glucose tolerance test is required to confirm whether you have gestational diabetes or not. Most women with a raised one-hour test will not have diabetes of pregnancy. If diabetes is confirmed, the outlook for mother and baby is excellent, provided that blood sugar monitoring for the rest of the pregnancy remains normal.

Other third trimester screening includes follow up scans for women with low-lying placentas, and further antibody screening at about 34 weeks for women who are Rhesus negative.

Although antenatal screening is not compulsory, very few women have objections to it. We appreciate that every woman will do all that she reasonably can to ensure safety for themselves and their baby in the course of the pregnancy and be fit and ready for the big day – your baby’s birthday!