Routine tests in first trimester


1. Blood and urine tests usually at 11-12 weeks – we require blood and 1 urine sample to perform these tests

a) Full blood count (FBC) – screens fo anaemia and thalassaemia. Tests for anaemia (haemoglobin level less than 11.5 g / dl), alpha- or beta- thalassaemia (MCV less than 80 fl is a good screening test). Haemoglobin electrophoresis is indicated if MCV is less than 80 fl, and would include the FBC and haemoglobin electrophoresis of the partner as well. DNA gene probes for thalassaemia may be indicated if alpha thalassaemia is suspected.

b) Infection screen for Hepatitis B, syphilis, HIV (human immunodeficiency virus) and CMV (cytomegalovirus). If positive, there are strategies to reduce the risk of transmission of the infection to the baby.

c) Immunity screen for Rubella - If negative, consider rubella vaccination before the next pregnancy. It prevents the potential of contracting rubella during the first or second trimester of pregnancy that may affect the fetus severely.

d) Pre-exisiting diabetes mellitus – glucose and HbA1c levels.

e) Blood group and Rhesus type - This screens for Rhesus negative state in the mother. If the mother is Rhesus negative, injection with Rhogam injections during certain scenarios would reduce the risk of a blood problem to future, or even current, babies.

f) Screening for antibodies to atypical red blood cell antigens - This screens for potentially harmful antibodies in the mother that could cross the placenta and bind to the red blood cells of the fetus and possibly causing heart failure in the foetus, and also possible antibodies that may cause a reaction if an incompatible blood type is used for blood transfusion.

g) Placental growth factor (PlGF) - This allows for more accurate calculation of the risk of pre-eclampsia and intrauterine growth restriction before 37 weeks. Low dose aspirin started before 16 weeks reduces the risk of pre-eclampsia and intrauterine growth restriction before 37 weeks for those who are judged to be high risk.


h) Screen for asymptomatic urinary tract infection with urine microscopy. If it shows possibility of urinary tract infection, a urine culture would be indicated and antibiotics may be necessary as it may reduce the risk of late miscarriages and preterm labour.

2. First Trimester Scan (FTS) between 12-13 weeks

The FTS is designed to screen for 4 groups of problems in pregnancy:

a) Risks of common chromosomal abnormalities (including Down syndrome [Trisomy 21], Edward syndrome [Trisomy 18] and Patau syndrome [Trisomy 13]) using Fetal Medicine Foundation (FMF) software. This allows the detection of 90% of Down syndrome, 90% of Edward syndrome and 90% of Patau syndrome.

b) Early structural abnormalities such as anencephaly (absence of skull), exomphalos (protrusion of intestines through an abdominal wall defect), megacystis (enlarged bladder), etc.

c) Risk of early pre-eclampsia requiring delivery 37 weeks (i.e. a serious condition during pregnancy characterised by high blood pressure with proteins in the urine). If left untreated, pre-eclampsia tends to progress and may become very serious. As the treatment of pre-eclampsia is delivery, we are most worried if the pre-eclampsia occurs early (i.e. before 37 weeks) which may require us to delivery early. If the risk of pre-eclampsia is raised, calcium supplementation of at least 1 g / day and low dose aspirin of 150 mg taken in the night reduce the risk of this complication.

d) Risk of fetal growth restriction before 37 weeks which may require early delivery. If fetal growth restriction is detection, the fetus needs to be closely monitored with fetal movement chart, regular measurements of the fetus and regular Doppler studies of the blood flow within the baby, and also cardiotocography (CTG) later in the third trimester. When the fetal status is non-reassuring, early delivery may be indicated. Low dose aspirin of 150 mg taken in the night and calcium supplementation of at least 1 g / day may reduce the risk of fetal growth restriction. However, there is less data on low dose aspirin for prevention of this condition.

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