Glossary: Terms Starting with "L"

The LH surge is a sharp, brief rise in luteinizing hormone that your body releases from the pituitary gland, typically 24 to 36 hours before an egg is released from the ovary. Detecting this surge is one of the most reliable ways to predict your most fertile days. Ovulation predictor kits measure LH in your urine and show a positive result when the surge is detected. Once you see a positive result, having intercourse within the next 12 to 36 hours gives the best chance of fertilisation. The surge itself lasts only one to two days.

Related: OPK, ovulation

LMP stands for last menstrual period, meaning the first day of your most recent period before you became pregnant. Doctors use this date to estimate how far along your pregnancy is, because the exact date of ovulation and conception is often unknown. Pregnancy is counted as 40 weeks starting from the LMP, even though conception typically happens around week two. If your cycles are irregular or longer than 28 days, the LMP-based estimate may be inaccurate. In that case, an early ultrasound scan, usually done between 8 and 12 weeks, gives a more reliable dating of your pregnancy.

Related: EDD, gestational age

Late term describes pregnancies that have reached 41 weeks 0 days through 41 weeks 6 days. At this stage, the baby is fully developed but the placenta may begin to work less efficiently, and the risk of complications such as meconium aspiration, cord compression, and stillbirth gradually increases. Most obstetricians in Singapore will recommend induction of labour somewhere between 41 and 42 weeks if spontaneous labour has not begun. Monitoring becomes more frequent in this period, typically including non-stress tests and amniotic fluid assessments. If your pregnancy reaches late term, stay in close contact with your care team and report any reduction in fetal movement immediately.

Related: Postterm, induction

Lightning crotch is a common informal term for the sudden, sharp, electric shock-like shooting pains felt deep in the pelvis, vagina, or rectum during the second or third trimester. These brief but intense jolts are thought to be caused by the baby pressing on pelvic nerves, particularly the pudendal nerve, as the baby grows and descends. The sensation can stop you in your tracks but typically lasts only a second or two. It is especially common as the baby drops lower in preparation for birth. Changing position, prenatal yoga, and wearing a belly support band may reduce how often it happens.

Related: Pelvic pressure, baby dropping

Lightening happens when your baby settles deeper into your pelvis in the weeks before birth. You may notice you can breathe more easily because the baby is no longer pressing up against your diaphragm, though you may feel more pressure on your bladder and need to urinate more often. For first-time mothers, lightening often occurs two to four weeks before labor begins. For women who have given birth before, it may not happen until labor actually starts. Not every mother feels a noticeable difference, and lightening alone does not mean labor is imminent.

Related: Engagement, baby dropping

The latent phase is the earliest part of labor, when your cervix gradually softens, thins out (effaces), and begins to open to around 4 to 6 centimetres. Contractions during this phase may feel irregular, ranging from mild period-like cramps to waves that come and go every 5 to 20 minutes. This phase can last anywhere from a few hours to more than a day, especially for first-time mothers. You are generally encouraged to stay home, rest, eat lightly, and keep yourself distracted. Contact your hospital if contractions become very painful, your waters break, or you notice bleeding.

Related: First stage, active labor

A good latch means your baby takes a wide mouthful of breast tissue, not just the nipple, allowing them to draw out milk efficiently without causing you pain. Signs of a deep latch include your baby's lips flanged outward, their chin pressing into your breast, and their nose staying clear of obstruction. A shallow latch is one of the most common causes of sore or cracked nipples and poor milk transfer, leading to a hungry, frustrated baby. Learning the correct position and angle early, ideally in the first hours after birth, makes breastfeeding far more sustainable.

Related: Colostrum, lactation consultant

A lactation consultant is a healthcare professional who specialises in supporting breastfeeding and chestfeeding. The gold-standard credential is IBCLC, International Board Certified Lactation Consultant, which requires hundreds of clinical hours and a rigorous exam. They can assess your latch, identify issues like tongue-tie or low supply, guide you on pumping and milk storage, and help you navigate challenges such as mastitis or nipple pain. Seeing one early, ideally in the first week postpartum, can make the difference between giving up and a long, comfortable feeding journey.

Related: Latch, milk supply

A late preterm baby is born between 34 and 36 completed weeks of pregnancy, just a few weeks before the full-term mark of 37 weeks. Although these babies often look similar in size to full-term newborns, their brains, lungs, and liver are still maturing. They are at higher risk for breathing difficulties, feeding problems, jaundice, and low blood sugar. Most late preterm babies need extra monitoring in hospital and may require a longer stay. Parents should watch for signs of poor feeding, excessive sleepiness, or yellowing of the skin and seek prompt medical review.

Related: Preterm, early term

Low birth weight (LBW) describes any baby born weighing less than 2,500 grams, regardless of how many weeks of pregnancy have passed. A baby can be low birth weight because they were born early (preterm) or because they did not grow well in the womb (intrauterine growth restriction). LBW babies are at greater risk of hypothermia, low blood sugar, infection, and feeding difficulties in the newborn period. Longer term, research links low birth weight to a higher risk of certain chronic conditions. Close monitoring, adequate nutrition, and keeping the baby warm are the most important early priorities for parents and care teams.

Related: Preterm, SGA

Large for gestational age (LGA) means a baby's birth weight is above the 90th percentile for their gestational age and sex. These babies weigh more than 90% of babies born at the same point in pregnancy. LGA is commonly linked to gestational diabetes, as excess blood sugar crosses the placenta and causes the baby to grow larger than expected. LGA pregnancies carry a higher risk of shoulder dystocia during vaginal delivery, where the baby's shoulder gets stuck after the head is born. Your doctor may recommend an elective caesarean section or early induction depending on the estimated fetal weight and your birth preferences.

Related: Macrosomia, GDM

Lochia is the vaginal discharge that occurs after giving birth, whether vaginally or by caesarean section, as your uterus sheds its lining and heals. It typically lasts 4 to 6 weeks and changes in colour and volume over time. In the first few days it is bright red and heavy, then it becomes a pinkish-brown over weeks two and three, and finally turns a yellowish-white before stopping. Using maternity pads rather than tampons during this time reduces infection risk. Lochia has a mild, earthy smell. A foul odour, sudden return of heavy bright-red bleeding, or passage of large clots can indicate a problem that needs prompt medical attention.

Related: Postpartum bleeding, uterus