Glossary: Terms Starting with "I"

Implantation is the process by which a fertilised egg, now called a blastocyst, burrows into the lining of the uterus (endometrium) to establish a pregnancy. It typically occurs 6 to 10 days after ovulation. Once the blastocyst embeds successfully, it begins producing the hormone hCG, which signals the body to maintain the uterine lining and support early pregnancy. Successful implantation depends on a receptive uterine lining and a healthy embryo. If the embryo does not implant, the lining sheds and menstruation occurs. This is a natural step that even healthy embryos sometimes do not complete.

Related: Embryo, hCG

Implantation bleeding is light spotting that some people experience when the fertilised egg embeds into the uterine lining, usually around 6 to 12 days after ovulation. It tends to be very light, pink or brown in colour, and lasts only a day or two, unlike the heavier flow of a period. Not everyone experiences it, and many people mistake it for an early period. If you notice light spotting around the time your period is due and a pregnancy test later comes back positive, this may have been implantation bleeding. Any heavy bleeding or pain warrants prompt medical review.

Related: Spotting, hCG

Induction of labor means your care team uses medical methods to start contractions before they begin on their own. Common reasons include going past 40 to 41 weeks, gestational diabetes, preeclampsia, reduced fetal movement, or your water breaking without contractions starting. Methods include a cervical gel or tablet (prostaglandins) to soften and open the cervix, a small balloon catheter, or a drip of synthetic oxytocin called Syntocinon. Induced labors can take longer to get going and may feel more intense, so discuss your pain relief options with your doctor or midwife beforehand.

Related: Cervical ripening, Pitocin

Intrauterine growth restriction (IUGR) is an older term describing a baby who is not growing at the expected rate inside the womb. The preferred term today is fetal growth restriction (FGR), but IUGR remains widely recognised. It occurs when the placenta cannot deliver enough oxygen and nutrients to support normal fetal growth, often due to placental insufficiency, maternal high blood pressure, preeclampsia, smoking, or infections. IUGR is diagnosed through serial ultrasound scans measuring the baby's head, abdomen, and femur length, alongside Doppler blood flow studies. Babies with IUGR may need early delivery and extra monitoring after birth.

Related: FGR, SGA