What Is a Placenta? Your Baby's Lifeline, Explained

• The placenta is a temporary organ that develops with your baby and acts as their lungs, gut, kidneys, and a hormone factory until birth.
• Oxygen, nutrients, antibodies, and waste pass between you and your baby across a thin membrane — your blood and your baby's blood never directly mix.
• Where the placenta sits matters: a low-lying placenta or placenta previa is checked again in the third trimester because most move up as the womb grows.
• Common placental problems — previa, abruption, insufficiency, and the accreta spectrum — are exactly what your anomaly scan and Doppler checks are looking for.
• After birth, delivering and inspecting the placenta is the third stage of labour; delayed cord clamping and active management are now standard, evidence-based care in Indian maternity units.
• Any vaginal bleeding, severe abdominal pain, or reduced baby movements in pregnancy needs urgent assessment — these can be signs of a placental problem.

The placenta is a disc-shaped organ that develops from both your tissue and your baby's tissue during pregnancy. It is genuinely temporary — it exists for one pregnancy, does its job, and is expelled within minutes of your baby's birth.

It begins very early. The placenta originates from the trophoblast cells that surround the embryo at implantation, around 6 to 8 days after fertilisation. These cells burrow into the lining of your womb, open up the small maternal arteries there, and create a space where your blood pools and bathes the baby's side of the placenta. This is where all the exchange between you and your baby happens.

By 10 to 12 weeks, the placenta is functionally established and has taken over hormone production from the ovary. It keeps growing through pregnancy, reaching around 500 to 700 grams at term — roughly one-sixth of your baby's birth weight. The mature placenta is about 15 to 22 cm across and 2 to 3 cm thick at the centre. One side faces the wall of your womb; the other faces the bag of waters where your baby lies, and the umbilical cord usually arises from near its centre.

Inside, the placenta is divided into 15 to 20 functional units called cotyledons. Within each, the baby's blood vessels branch into fine villi that float in a pool of your blood. Gases, nutrients, and waste cross the thin membrane between the two — but the two bloodstreams never mix directly in a normal pregnancy. This is exactly why a mother and baby with different blood groups can share a pregnancy safely.

The umbilical cord is the lifeline between baby and placenta — about 50 to 60 cm long at term, with two arteries carrying used blood from baby to placenta and one vein carrying fresh, oxygen-rich blood back. It is cushioned by a jelly-like substance (Wharton's jelly) that stops it kinking. How the cord joins the placenta varies — usually central, sometimes at the edge, and rarely into the membranes (a velamentous insertion, which carries a slightly higher bleeding risk). The cord insertion is one of the small details noted on your mid-pregnancy anomaly scan.

The placenta does every essential job your baby's own organs are not yet ready to do.

Breathing for your baby. Your baby does not breathe air in the womb — their lungs are filled with fluid. All their oxygen comes from your blood, crossing the placenta and travelling to your baby through the umbilical vein. The carbon dioxide your baby makes travels back and is breathed out by you. This is why anything that reduces blood flow to the placenta — low maternal blood pressure, lying flat on your back late in pregnancy, or a placental problem — can stress the baby. The late dips seen on the baby's heart-rate trace (CTG) in labour are the visible sign of this.

Feeding your baby. Glucose, amino acids, fats, water, vitamins, and minerals all cross from you to your baby. The placenta is selective — it carries across what your baby needs and largely keeps out what would harm them.

Removing waste. Waste products from your baby's metabolism cross the placenta in the opposite direction and are cleared by your own kidneys.

Making hormones. The placenta is one of the body's largest hormone factories during pregnancy. It makes hCG (the hormone a pregnancy test detects), progesterone and estrogen (which hold the pregnancy and prepare your breasts), and human placental lactogen, which adjusts how your body handles sugar so your baby gets enough — and which contributes to gestational diabetes in some women.

Protecting your baby. From around 20 weeks, your protective antibodies (IgG) cross the placenta and give your newborn passive immunity for their first few months. This is exactly why vaccines given in pregnancy — against tetanus, whooping cough, flu, and COVID-19 — protect the baby too. The placenta also blocks many infections, though some can still cross. And it quietly stops your immune system from rejecting your baby, who is genetically half-foreign to you — one of the great unsolved puzzles of pregnancy.

Where the placenta has implanted is one of the key things checked on the routine anomaly scan at 18 to 22 weeks. The placenta can lie on the front wall (anterior — you may feel kicks a little less, because they are cushioned), the back wall (posterior — kicks often feel sharper and earlier), the top (fundal), the side, or low down near the cervix. The position itself rarely affects how well the placenta works — but its position relative to the cervix matters a lot for how you give birth.

Placenta previa is when the placenta partly or fully covers the inner opening of the cervix. It is the most important positional finding. A placenta completely covering the opening makes vaginal birth impossible and means a planned caesarean, usually around 36 to 37 weeks. A placenta within 2 cm of the opening is also usually delivered by caesarean. True placenta previa at term affects roughly 0.5 percent of pregnancies — much less common than the low-lying placentas seen at the mid-pregnancy scan, because the lower womb stretches as pregnancy advances and many of these effectively move up and out of the way. You can read more in our dedicated guide to placenta previa.

The usual Indian protocol is simple: check position at the 18 to 22 week scan; if low-lying or previa is seen, repeat the scan at 32 to 34 weeks; if the placenta is still covering or within 2 cm of the cervix, plan a caesarean. If you have previa, you will be advised to avoid penetrative sex, to go to the labour ward immediately for any bleeding, and you may be admitted if bleeding occurs.

Placenta accreta spectrum (accreta, increta, percreta) is more serious — the placenta grows too deeply into or through the wall of the womb and does not separate cleanly after birth. It is strongly linked to previous caesareans, especially a previa lying over an old scar. As caesarean rates have risen, so has this condition. It is planned for in advance at a tertiary centre with a full surgical team, and it is one of the strongest reasons not to have an unnecessary first caesarean — the risk carries into future pregnancies.

• Vaginal bleeding at any stage of pregnancy
• Severe or constant abdominal pain, or a hard, tender belly
• Reduced or absent baby movements
• A baby measuring smaller than expected on scans
• Severe headache, vision changes, or swelling (possible preeclampsia, a risk factor for abruption and insufficiency)

The third stage of labour is the stretch from the birth of your baby to the delivery of the placenta. It usually takes a few minutes with modern care. After the baby is born, the womb keeps contracting; the placenta cannot shrink with it, so it peels away from the wall and is delivered. The same powerful contraction then clamps down on the blood vessels that fed the placenta — this is your body's main way of stopping bleeding after birth.

Active management of the third stage is the WHO-, FIGO-, and FOGSI-recommended approach, and the standard in Indian maternity units. It has three parts: a uterotonic drug (oxytocin 10 IU into the muscle within one minute of birth), gentle controlled cord traction once the placenta has separated, and a check that the womb is firm afterwards. This roughly halves the risk of postpartum haemorrhage compared with simply waiting — and postpartum haemorrhage is one of the leading causes of maternal death in India, which is why this is done for almost every birth.

The signs the placenta has separated are a small gush of blood, the cord lengthening at the opening, and the womb becoming firm and globe-shaped. The placenta is then delivered slowly and inspected straight away to make sure nothing is left behind. Bleeding is watched closely for the first hour, and you are checked for tears — part of the wider picture of normal postpartum bleeding and its red flags.

A retained placenta — when the placenta does not deliver within about 30 minutes despite active management — happens in around 1 to 3 percent of vaginal births. It may need manual removal in theatre under anaesthesia with antibiotic cover. Left-behind fragments are a major cause of later bleeding and infection, which is why the placenta is always examined for completeness. Our guide to a retained placenta explains the symptoms and treatment.

Checking the placenta after birth is a standard, quick part of care, and it is written into your labour record.

The maternal side — the rough surface that was attached to your womb — is examined first to confirm all the cotyledons are present. Any gap suggests a retained fragment that must be removed. This side is also checked for calcification (normal at term), infarcts (areas of old, dead tissue, more common with high blood pressure or insufficiency), and clots behind the placenta that hint at an abruption.

The fetal side — the smooth, shiny surface — is checked next: where the cord joins, the cord length, any true knots, and that the cord has its normal three vessels (two arteries, one vein). A single artery, seen in about 1 percent of pregnancies, prompts a careful newborn check. The membranes are traced to make sure none are left behind.

The placenta is weighed (normally 500 to 700 grams). A small placenta can go with a small baby; a large one with maternal diabetes or severe anaemia. Routine lab examination of the placenta is not done for every birth in India, but it is recommended in specific situations — severe growth restriction, suspected infection, severe preeclampsia, stillbirth, suspected abruption or accreta, and twin pregnancies.

Disposal follows hospital policy. In most Indian hospitals the placenta is treated as clinical waste and incinerated. Many families ask to take it home for cultural reasons, which hospitals usually allow if requested in advance and biohazard rules are followed.

When to clamp the umbilical cord after birth has shifted decisively over the past two decades. The old habit of clamping within seconds — partly for convenience, partly on a now-disproven belief that it reduced jaundice — has given way to delayed cord clamping, recommended by WHO, FIGO, NICE, RCOG, ACOG, and FOGSI.

The current advice is to wait at least 60 seconds before clamping in term babies (and at least 30 seconds, usually longer, in preterm babies), as long as the baby does not need urgent resuscitation. During this wait, the placenta continues to transfuse blood into the baby.

In a term baby this transfers around 80 to 100 ml of extra blood — roughly a third of their blood volume — and meaningfully improves iron stores at six months. That matters a great deal in India, where iron deficiency in infancy is common and is linked to developmental delays. Delayed clamping reduces iron deficiency at 6 months by around 30 percent. In preterm babies the benefits are even greater — fewer transfusions, less bleeding in the brain, and less bowel disease.

In practice, the baby is kept at the level of the placenta during the short wait while the oxytocin is still given to you within a minute of birth. The few situations where it is not done include a baby needing immediate resuscitation that cannot happen with the cord intact, or a maternal emergency such as heavy bleeding. If you are planning cord blood banking, discuss it in advance, as it interacts with clamping timing. Delayed clamping is now standard in most NABH-accredited Indian units and part of the national LaQshya labour-room quality programme — one of the simplest, cheapest, most effective things modern birth care offers.

Beliefs and rituals around the placenta run deep across India. In many Hindu traditions the placenta is considered sacred and is buried in the earth, sometimes with a tree or plant placed over it as a living symbol of the birth. In some communities it has a specific role in postnatal rituals or is thought to carry protective significance for the mother. In others it is disposed of practically as clinical waste.

Modern Indian hospitals generally accommodate a family's wish to take the placenta home if it is requested in advance and biohazard protocols are followed — usually handed over in a sealed container. Be aware that it is biological tissue and breaks down quickly, so refrigeration or prompt burial is needed. If there is a medical reason to send it to the lab (such as severe growth restriction, suspected infection, or stillbirth), that examination is done first.

A separate conversation has grown around placental encapsulation — drying the placenta and grinding it into capsules to swallow, promoted in some Western wellness circles for mood, milk supply, and energy. The evidence of benefit is poor, the risk of bacterial contamination is real, and FOGSI does not endorse it; the US CDC has even reported a newborn infection traced to contaminated placenta capsules. There is no traditional Indian practice of eating the placenta, and the mainstream medical view is against it. Our deeper look at eating the placenta lays out the evidence. If your concern is postnatal mood or milk supply, far stronger help exists — good breastfeeding support, rest, nutrition, and treatment of postnatal depression where it is present.

• WHO — Guideline: Delayed umbilical cord clamping for improved maternal and infant health and nutrition outcomes
• WHO — Recommendations for the prevention and treatment of postpartum haemorrhage
• ACOG — Placenta Accreta Spectrum (Obstetric Care Consensus)
• NHS — Placenta complications (low-lying placenta, placenta praevia, accreta)
• RCOG — Placenta Praevia and Placenta Accreta: Diagnosis and Management (Green-top Guideline No. 27a)
• FIGO — Recommendations on the management of postpartum haemorrhage