Common Medical Tests in Pregnancy

Published on: March 11, 2019

Whether it’s a first-time pregnancy or not, navigating healthcare in Bangkok can be scary and costly. Midwife Emma McNerlin explores common routine tests offered in pregnancy.

By Emma McNerlin

When you decide on a hospital you will either choose or be allocated an OB/GYN to oversee your care. Each doctor has a different approach or standards of care, so it’s important to discuss birthing plans early on to establish that she/he is the right one for you. This gives you time to change doctors or hospitals if necessary. However, take note that blood tests sometimes need to be repeated when you switch hospitals.

When it comes to tests offered in prenatal care, these are often not explained well. Be aware that you can decline any test or ask your doctor for more details, including the costs, before consenting to tests. Insurance plans vary greatly in their coverage for prenatal care, so it is important that you fully understand the tests being offered. The following are the basic tests offered in a typical low-risk pregnancy.

Tests can and should be offered, but it should be your choice to accept or decline them.

Blood pressure and urine tests

These take place at each appointment, usually conducted by a nurse/midwife prior to seeing your doctor. They are standard tests to screen for a serious condition of pregnancy called pre-eclampsia, diagnosed by a marked rise in blood pressure and the presence of protein in the urine. On the first visit, blood pressure tests are usually taken on both arms, and the right arm thereafter. When collecting urine for testing, always capture the mid-stream urine to ensure an untainted sample. You can do this by allowing urine to flow for a few seconds before collecting the sample in a clean container.


These are measured at your first appointment to calculate your Body Mass Index (BMI). A high or low BMI (>30 or <17) may indicate increased risk factors in pregnancy. In a healthy single pregnancy, you can expect to gain between 10 to 15kg, mostly in the late second and third trimesters. Weighing at each appointment is not necessary.


Ultrasound scans are very popular among OB/GYNs here, though they can be a costly addition to your care if done at every appointment. From a clinical perspective, an ultrasound scan is recommended between 8-12 weeks to date your pregnancy and then between 18-22 weeks for an anomaly scan to check for physiological defects in the organs and limbs. In a healthy low-risk pregnancy, no further scans are required.

Clinical indications for further scans include issues with baby’s growth, the amount of amniotic fluid, placental position (low placenta at 20 weeks usually indicates a repeat scan at 32 weeks), queries regarding baby’s presentation (e.g., breech or transverse lie), reduced fetal movement, or maternal conditions including high blood pressure or diabetes in pregnancy.

If you are not sure what the indication is for further scans, ask your doctor to explain more. Extra scans, whilst not always medically indicated, will often be offered as standard, but are charged as an extra on the bill, so if in doubt ask why your doctor needs to scan.

Genetic screening tests

You will also be offered screening tests to determine the risk of your baby having a genetic condition such as Down Syndrome. There are a variety of screening tests on offer, and these vary greatly in sensitivity and price. The triple test taken before 12 weeks involves a blood screening and measurement on scan of the nuchal fold of the baby’s neck to determine a risk factor for Trisomy 21 (Down Syndrome), which is around 65% sensitive with 5% false positive.

More sophisticated and expensive tests such as NIFTY and Panorama detect tiny strands of fetal DNA in the maternal bloodstream from as early as the 9th week of pregnancy — these are around 95-97% sensitive with less than 1% false positive rate.

Should you test as high risk by any of these methods, you will be offered further diagnostic testing and counseling. Any genetic screening test is optional, and you should discuss your wishes with your doctor.

Blood tests

Serology tests

You will be offered screening at the start of your pregnancy to check whether you have certain sexually transmitted or blood-borne disorders that could affect your baby’s health, namely Hepatitis B, Syphilis, and HIV. If you test positive for any of these conditions, tailored care in pregnancy can ensure that you do not pass them onto your baby. Some doctors will look to repeat these tests several times throughout your pregnancy and in labor.

It is up to you whether to accept or decline the testing, though declining to be tested may impact the plan made by the pediatrician once your baby is born. You will also be checked to ensure that you are immune to German measles (Rubella), which can cause birth defects if contracted in pregnancy. If you are not immune, you will be offered immunization after your baby is born to protect future pregnancies.

Blood group

The hospital will seek to establish your blood group (A, B, AB, or O) and your rhesus status (positive or negative). If you are rhesus (-), you may be offered an injection of RhoGAM (Anti-D) at 28 weeks to protect you from mounting an immune response to potential micro-mixing of your blood with baby’s blood. Your doctor can provide you with all the relevant information should this be the case.

Iron level (Hb)

The iron (hemoglobin) in your blood is checked at the start of pregnancy. If this is deemed low (<11g/dl), you will be advised to take iron supplements in pregnancy and will be re-tested again at 28 and 36 weeks. As baby takes most of its iron requirements for its first six months after birth from you in-utero, it is important that you maintain healthy iron levels to avoid excessive tiredness, breathlessness, and increased risk of bleeding at birth.

Sickle cell/thalassemia

Your blood cells are examined under a microscope to rule out sickle cell anemia and thalassemia which, if present in both parents, can be passed to the baby and can be a serious condition.

Gestational diabetes (GDM)

Women of Southeast Asian, Afro-Carribean and Middle Eastern origin are genetically more predisposed to developing diabetes in pregnancy. Previous birth of a baby over 4.5kg, a family history of GDM or Type II Diabetes, or being overweight also increases your risk of developing GDM. In Bangkok, random glucose screening is offered to all pregnant women around 28 weeks, and if results are high, more extensive testing of fasting oral glucose tolerance is conducted. Discuss your risks and options for testing for GDM with your doctor.

Group B Strep (GBS)

Group B Strep is a usually healthy transient colonization of vaginal bacteria thought to be present in around 25% of women’s vaginas. In labor and birth, a small number of babies born to GBS-positive women go on to develop life-threatening, early-onset GBS infection. Overall, this infection affects 1 in 1,750 babies born and usually manifests in the first few days of life. Pregnant women are screened for GBS by a low vaginal swab (like a big cue-tip) in the vagina which is sent for culturing. Women who test positive are offered IV antibiotics in labor, which reduces the already small risk of the baby contracting early-onset GBS to almost zero.

For most women, pregnancy is a normal physiological process. By the time you reach the end of your pregnancy, it is possible that you will have had a battery of screening and tests listed above, all of which are designed to provide reassurance of a healthy pregnancy or in some rare cases an early indication of any risk.

Tests can and should be offered, but it should be your choice to accept or decline them. If you are unclear as to what any test is for, always ask your OB/GYN, especially if it is a repeat test for something that you have already tested negative for.

Antenatal care is not usually included in the birth package you choose at the hospital. Blood tests, scans, and prenatal appointments are billed separately and can be costly, especially if tests are repeated without medical indication. Being informed and proactive will help to ensure that you are in partnership with your doctor in ensuring the best care for you and your baby.

The content of this article is intended only for information purposes, not as medical advice. As with all health matters pertaining to pregnancy, please consult with your OB/GYN.

Photos by Bokskapet, John Looy and Rawpixel on Unsplash.




About the Author

Originally from Ireland, Emma is a UK-trained midwife who worked in the maternity unit at a busy NHS hospital just outside London. Emma moved to Bangkok with her husband in 2014; they have an 11-year-old son, Toby. Volunteering with BAMBI Bumps and Babies since August 2015, Emma regularly conducts sessions on pregnancy, birth, breastfeeding and Infant First Aid. In her spare time, she enjoys baking and Muay Thai, and is an active member of her son’s parent group at school.

The views expressed in the articles in this magazine are not necessarily those of BAMBI committee members and we assume no responsibility for them or their effects.

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