Glossary: Terms Starting with "C"

Cervical mucus is a fluid produced by glands in the cervix that changes in texture and volume throughout your menstrual cycle, driven by oestrogen and progesterone. In the days before ovulation, mucus becomes clear, slippery, and stretchy, similar to raw egg white, which allows sperm to survive and travel toward the egg more easily. After ovulation it becomes thicker and cloudy, forming a barrier. Tracking these changes each day, alongside other fertility signs like BBT, gives you a clearer picture of your fertile window and can improve your chances of conceiving.

Related: Fertile window, ovulation

A chemical pregnancy is an early pregnancy loss that happens shortly after implantation, usually within the first five weeks. The embryo produces enough hCG to trigger a positive pregnancy test, but it stops developing before a heartbeat or gestational sac can be seen on ultrasound. Many women experience a chemical pregnancy without realising it, as the loss often looks like a slightly late or heavier period. While it can be emotionally painful, especially after fertility treatment, a chemical pregnancy does not usually indicate a fertility problem. Most women go on to have a healthy pregnancy in subsequent cycles.

Related: hCG, early pregnancy loss

Crown-rump length (CRL) is the measurement taken on ultrasound from the top of the embryo's or fetus's head (crown) to the bottom of its bottom (rump), deliberately excluding the legs because they are curled up. This measurement is the most accurate way to estimate gestational age in the first trimester, typically between 6 and 14 weeks. A small change in CRL corresponds to a precise number of days of development, making it a reliable tool for confirming your due date early on. After 14 weeks, other measurements such as head circumference and femur length become more useful for tracking growth.

Related: Dating ultrasound, GA

Cell-free DNA (cfDNA) screening is another name for NIPT. During pregnancy, small fragments of DNA from the placenta enter your bloodstream. A blood sample is taken from you and analysed in a laboratory to look at these fragments for signs of chromosomal abnormalities. The test can be done from 10 weeks and is considered far more accurate than older combined first trimester screening for conditions like Down syndrome. Results are usually returned within one to two weeks. Because it looks at placental DNA rather than the baby's DNA directly, rare false positives and false negatives can occur.

Related: NIPT, NIPS

Chorionic villus sampling (CVS) is a diagnostic procedure performed between 10 and 13 weeks of pregnancy. A small sample of placental tissue, called chorionic villi, is taken either through the abdomen or the cervix using a fine needle or tube guided by ultrasound. The tissue shares the baby's genetic make-up, so it can be tested to diagnose chromosomal conditions like Down syndrome, as well as inherited genetic disorders such as thalassaemia. CVS provides a definitive yes or no answer, unlike screening tests. The procedure carries a small risk of miscarriage, generally estimated at around 0.5 to 1%, and should be performed by a trained specialist.

Related: Amniocentesis, diagnostic test

Constipation means having fewer than three bowel movements a week, or passing hard, dry stools that are difficult or painful to move. During pregnancy, the hormone progesterone relaxes the bowel muscles, slowing digestion. Iron supplements, which many Singapore mums take throughout pregnancy, make this worse. As your uterus grows it also puts pressure on your bowel. To ease constipation, increase fiber through fruits, vegetables, and wholegrain bread, drink at least eight glasses of water daily, and take short walks regularly. If diet changes are not enough, your doctor or midwife can recommend a safe stool softener. Straining too hard can lead to hemorrhoids, so act early.

Related: Hemorrhoids, iron

The cervix is the narrow, lower end of the uterus that connects it to the vagina. During pregnancy it stays firm and closed, sealed by a mucus plug that protects the baby from infection. As labor approaches, the cervix softens (ripens), shortens (effaces), and gradually opens (dilates) to allow the baby to pass through. Your doctor or midwife may perform an internal examination to assess how dilated and effaced your cervix is during late pregnancy or active labor. Dilation is measured in centimeters, with 10 cm being fully open and ready for pushing.

Related: Dilation, effacement

Cervical length refers to the measurement of your cervix taken via transvaginal ultrasound, usually between 18 and 24 weeks of pregnancy. A longer cervix generally indicates a lower risk of early labor. A typical measurement in mid-pregnancy is around 35 to 48 mm. Your doctor may recommend this scan if you have had a previous preterm birth, a prior cone biopsy, or are carrying twins. The result is always interpreted alongside your full clinical history, because a single number does not tell the whole story on its own.

Related: Short cervix, cerclage

Cerclage is a minor surgical procedure where a doctor places a strong stitch around the cervix to keep it closed during pregnancy. It is recommended for women with cervical incompetence, meaning the cervix begins to shorten or open too early, which can lead to miscarriage or premature birth. The stitch is usually placed between weeks 12 and 14, and removed around week 36 to 37 when it is safe for labour to begin. Your doctor will monitor cervical length with ultrasound scans to decide if cerclage is the right option for you.

Related: Short cervix, cervical insufficiency

A contraction is the rhythmic tightening and relaxing of the uterine muscle that helps open the cervix and push your baby down during labor. Real labor contractions become progressively longer, stronger, and closer together over time. Early contractions may feel like strong period cramps or a tightening across the abdomen and back. You can time them from the start of one to the start of the next. Most hospitals advise heading in when contractions are 5 minutes apart, lasting about 1 minute, for at least 1 hour. Braxton Hicks contractions, sometimes called practice contractions, are irregular and usually painless, and they do not cause cervical change.

Related: Braxton Hicks, dilation

Crowning happens during the pushing stage of labor when the widest part of your baby's head becomes visible at the vaginal opening and stays visible between contractions, rather than slipping back. This is a sign that birth is very close. You may feel an intense burning or stretching sensation, sometimes called the "ring of fire." Your midwife or doctor will guide you to slow your pushing at this point to allow tissues to stretch gradually, which can reduce tearing. Warm compresses, controlled breathing, and gentle perineal support from your care team all help during crowning.

Related: Pushing, second stage

Cardiotocography, or CTG, is a test that records two things at the same time: your baby's heart rate and your uterine contractions. Two sensors are placed on your abdomen and held with elastic belts. The machine prints a paper trace or displays readings on a screen. Doctors and midwives look for patterns that show the baby is getting enough oxygen. A normal CTG shows a baseline heart rate of 110 to 160 beats per minute, regular small variations, accelerations with movement, and no concerning dips called decelerations. Abnormal patterns may prompt further assessment or a change in your care plan.

Related: Fetal monitoring, contractions

Cervical ripening refers to the process of softening, thinning, and opening the cervix to prepare it for labor. Before a doctor can induce labor, the cervix often needs to be made more favorable. Methods include prostaglandin gels or tablets placed near the cervix, a small balloon catheter inserted to gently stretch the opening, or oral medications like misoprostol. The approach depends on how far along the cervix has already changed, the baby's position, and the mother's health history. Ripening usually happens in the hospital over several hours, and the care team monitors both mother and baby throughout the process.

Related: Induction, Foley balloon

A cesarean birth is a surgical procedure where your doctor makes an incision through your abdomen and uterus to deliver your baby. It usually takes around 45 minutes and is performed under regional anesthesia, so you are awake but feel no pain below your waist. A cesarean may be planned ahead of time or happen urgently during labor. Recovery takes longer than a vaginal birth, typically four to six weeks, and you will have a small scar just above your pubic hairline. Most people go home within three to four days and can breastfeed and bond with their baby right away.

Related: VBAC, TOLAC

Cord blood is the blood left in your baby's umbilical cord and placenta immediately after birth. It is rich in haematopoietic stem cells, which can develop into different types of blood cells. These stem cells are used in treatments for certain cancers, blood disorders, and immune diseases. Parents can choose to donate cord blood for free to a public bank, where it may help other patients, or pay to store it in a private cord blood bank for their family's potential future use. The collection process is painless, takes only a few minutes, and does not affect your birth experience.

Related: Umbilical cord, DCC

Cephalic presentation means your baby is lying head-down in the uterus, which is the ideal and most common position for birth. The baby's head is closest to your cervix and will lead the way through the birth canal during labour. Most babies naturally settle into this position by 32 to 36 weeks of pregnancy as the heaviest part of their body, the head, gravitates downward. Cephalic presentation gives you the best chance of a straightforward vaginal delivery. Your midwife or doctor will confirm the baby's position at antenatal appointments through abdominal palpation and, if needed, an ultrasound scan.

Related: Breech, presentation

Colostrum is the thick, yellowish milk your breasts produce from about the third trimester through the first two to five days after birth. It comes in small amounts, typically just a few millilitres per feed, but that is exactly what a newborn's tiny stomach needs. Colostrum is packed with antibodies, white blood cells, and growth factors that protect your baby from infections and help seal their gut lining. It also acts as a gentle laxative, helping your baby pass meconium and reducing the risk of jaundice. Every drop counts.

Related: Milk coming in, latch

Cluster feeding is when your newborn wants to feed very frequently, sometimes every 30 to 60 minutes, in a concentrated stretch of a few hours, usually in the late afternoon or evening. This is normal newborn behavior driven by hunger, growth spurts, or a natural need for comfort and closeness. Cluster feeding also signals your body to produce more milk, so it serves an important supply-building purpose. It can feel exhausting and may make new parents worry that their milk is insufficient, but a baby who is producing enough wet and dirty nappies and gaining weight is usually feeding well. Try to rest between feeds and accept offers of help.

Related: Growth spurt, milk supply

Combination feeding means giving your baby both breast milk and infant formula, either at different feeds or within the same feed. Some parents start combination feeding from birth due to low supply or a NICU stay, while others introduce formula gradually when returning to work or as a way to share feeding duties with a partner. It can help extend your breastfeeding journey rather than ending it completely. To protect your milk supply, try to replace breastfeeds with pumping sessions when you substitute a formula feed. Combination feeding is a flexible approach and there is no single right way to do it.

Related: Formula feeding, pumping