Glossary: Terms Starting with "A"

Antenatal simply means before birth, and the term is widely used in Singapore, the UK, Australia, and most Commonwealth countries in place of the American term prenatal. Antenatal care includes the full range of support from your first booking appointment through to delivery, covering blood tests, scans, group B strep screening, and birth preparation classes. You may also hear antenatal used in phrases like antenatal depression, which describes low mood or anxiety during pregnancy, not just after. Knowing the term helps you understand clinic letters, hospital paperwork, and health resources from KKH or NUH without confusion.

Related: Prenatal, antenatal class

Amniocentesis is a diagnostic test usually performed between 15 and 20 weeks of pregnancy. Using continuous ultrasound guidance, a thin needle is passed through the abdomen into the uterus to withdraw a small sample of amniotic fluid, which contains cells shed by the baby. These cells are cultured and analysed to detect chromosomal conditions such as Down syndrome, as well as neural tube defects and some inherited genetic disorders. Results can take one to two weeks, though rapid testing for common trisomies may be available sooner. The procedure carries a small miscarriage risk of around 0.1 to 0.5% when performed by an experienced specialist.

Related: CVS, amniotic fluid

The anatomy scan is a detailed ultrasound performed between 18 and 22 weeks of pregnancy. A sonographer carefully examines your baby's brain, heart, spine, kidneys, limbs, and facial features to check that everything is developing normally. The placenta position and amniotic fluid levels are also assessed. If a low-lying placenta is spotted, a follow-up scan later in pregnancy is usually recommended. The scan takes around 30 to 45 minutes. While it detects many structural concerns, it cannot rule out every condition, so results should always be discussed with your obstetrician.

Related: Level II ultrasound, placenta

Abdominal circumference (AC) is the measurement taken around your baby's belly during an ultrasound scan. It is one of the key measurements used in your second and third trimester anomaly and growth scans. AC reflects the size of your baby's liver and the amount of fat stored under the skin, making it a good indicator of overall nutrition and growth. When combined with head circumference, femur length, and biparietal diameter, it helps your doctor estimate your baby's weight and check whether growth is on track. A reading that is too small or too large may prompt closer monitoring or further investigation.

Related: EFW, growth restriction

An antibody screen, sometimes called an indirect Coombs test, is a blood test done early in pregnancy to check whether your blood contains antibodies that could harm your baby. These antibodies can develop if you have received a blood transfusion in the past, had a previous pregnancy, or are Rh negative and were exposed to Rh-positive blood. If antibodies are found, your doctor will monitor you and your baby more closely throughout pregnancy, as certain antibodies can cross the placenta and destroy the baby's red blood cells. The test is painless and forms part of routine antenatal bloodwork at your booking visit.

Related: Rh factor, alloimmunization

The amniotic sac is a thin but tough pair of membranes, the amnion and chorion, that form a sealed, fluid-filled chamber around your growing baby inside the uterus. It protects your baby from bumps and pressure, helps maintain a stable temperature, and gives your baby room to move and develop normally. The sac usually ruptures at the start of labour, which is what people mean by "waters breaking." In some cases, doctors may rupture it artificially to speed up labour, a procedure called an amniotomy. A healthy, intact sac is essential for a safe pregnancy.

Related: Amniotic fluid, membranes

Amniotic fluid is the clear, yellowish liquid that fills the amniotic sac and cushions your baby throughout pregnancy. In early pregnancy it is mostly water from your body, but from around 20 weeks your baby's urine becomes the main source. The fluid lets your baby move freely, which is important for healthy muscle and bone development. Your baby also swallows and breathes the fluid, which helps the lungs and digestive system mature. Fluid levels naturally peak around 34 to 36 weeks and then gradually decrease toward your due date. Too much or too little fluid can be a sign that something needs attention.

Related: Amniocentesis, AFI

The amniotic fluid index, or AFI, is a measurement your doctor or sonographer takes during an ultrasound to estimate how much fluid is around your baby. The abdomen is divided into four sections and the deepest pool of fluid in each is measured in centimetres. The four numbers are added together to give the AFI score. A normal AFI is generally between 8 and 24 centimetres. An AFI below 5 to 8 may suggest oligohydramnios, while a score above 24 may indicate polyhydramnios. Both conditions can affect your baby's wellbeing and may need closer monitoring or treatment.

Related: Oligohydramnios, polyhydramnios

An anterior placenta is simply one that has attached to the front wall of the uterus, the side closest to your belly button. This is a normal finding and does not harm your baby. However, because the placenta acts as a cushion between your baby and your abdominal wall, you may feel your baby's kicks and movements later than expected, or they may feel more muffled and low. Kicks are often felt more strongly on the sides or lower abdomen. An anterior placenta can also make it slightly harder to hear the heartbeat clearly with a home doppler and may affect how amniocentesis is performed.

Related: Placenta, fetal movement

Active labor begins once the cervix reaches around 6 centimetres dilated and continues until it is fully open at 10 centimetres. Contractions become longer, stronger, and more regular, typically coming every 3 to 5 minutes and lasting 45 to 60 seconds. Most women find active labor significantly more intense than the latent phase and need focused breathing or pain relief to manage. This is the stage when most hospitals encourage you to come in. Cervical progress tends to be more steady during active labor, though the pace still varies from person to person.

Related: Dilation, transition

Augmentation of labor means helping a labor that has already begun but is moving too slowly or has stalled. Your doctor or midwife may suggest augmentation if contractions are too weak, too far apart, or have stopped progressing after your cervix started dilating. The most common method is an oxytocin drip (Syntocinon) given through an IV to strengthen and regularize contractions. Another approach is breaking the waters (amniotomy) to encourage stronger contractions. Augmentation is used to protect both mother and baby when slow labor raises concerns about infection, fetal distress, or exhaustion.

Related: Pitocin, amniotomy

Amniotomy is the deliberate breaking of the amniotic sac by a doctor or midwife using a small, thin hook called an amnihook. It is also called artificial rupture of membranes, or AROM. The procedure takes only seconds and is usually painless, though you will feel a warm gush of fluid. It is done to start or speed up labor, to check amniotic fluid color for signs of meconium, or to place an internal fetal monitor. Amniotomy is only performed after you are already in labor or being induced, and it commits your body to delivering within a certain time frame to reduce infection risk.

Related: ROM, water breaking

Assisted vaginal birth is when a doctor or midwife uses an instrument, either forceps or a vacuum cup, to help guide the baby out during the pushing stage of labor. This may be needed when labor is not progressing, when the mother is exhausted and cannot push effectively, or when the baby shows signs of distress and needs to be born quickly. It is performed under local or regional anesthesia to reduce pain. While it sounds alarming, assisted birth is a well-practiced skill that can prevent the need for emergency C-section when used at the right moment.

Related: Forceps, vacuum

The Apgar score is a quick health check given to newborns at 1 minute and again at 5 minutes after birth. A midwife or doctor assesses five signs: skin colour, heart rate, reflex response, muscle tone, and breathing effort. Each sign is scored from 0 to 2, giving a total out of 10. A score of 7 or above is considered healthy. A lower score means the baby may need extra support, such as warming, suctioning, or oxygen. The score helps the care team decide quickly if a baby needs immediate medical attention.

Related: Newborn assessment

Afterpains are cramping sensations caused by your uterus contracting after birth as part of the involution process. They feel similar to menstrual cramps or mild labour contractions and tend to be stronger with each subsequent pregnancy. Breastfeeding can intensify afterpains because nursing triggers oxytocin, which causes the uterus to contract more firmly. Most afterpains are strongest in the first two to three days postpartum and gradually ease off. Paracetamol or ibuprofen (if not contraindicated) can help manage the discomfort. Staying hydrated and emptying your bladder regularly also helps the uterus contract more efficiently and reduces pain duration.

Related: Uterine involution, oxytocin