Parturition in sheep unfolds in three recognized stages: cervical dilation, expulsion of the lamb, and delivery of the placenta. The entire process, from the first visible signs of restlessness to the passing of the afterbirth, typically takes a few hours in an uncomplicated birth, though substantial variation exists between breeds, litter sizes, and individual ewes. What makes sheep parturition especially interesting is that the lamb itself sets the whole process in motion, days before the ewe shows any outward sign of labor.
What Triggers Labor
Unlike many mammals where the mother’s hormones alone dictate timing, in sheep the fetus plays the starring role. In the final two weeks or so of gestation, the lamb’s adrenal glands begin producing increasing amounts of cortisol, with a sharp spike occurring in the last three to four days before birth.1PubMed. The trigger for parturition in sheep: fetal hypothalamus or placenta? This fetal cortisol acts on the placenta, triggering a cascade of hormonal changes in the ewe. Progesterone, which has been keeping the uterus quiet throughout pregnancy, drops sharply. Estrogen rises. That shifting ratio stimulates the production of prostaglandins, which soften the cervix and prime the uterine muscle for contractions.2Biology of Reproduction. Prostaglandin Regulation of Fetal Plasma Adrenocorticotropin and Cortisol Concentrations in Late-Gestation Sheep
The practical takeaway here is that premature lambs, or lambs whose adrenal function is compromised, can delay the onset of labor. This fetal-driven mechanism is why veterinary interventions to induce lambing sometimes target the same hormonal pathways. In one trial, both estradiol benzoate and dexamethasone (a synthetic corticosteroid) successfully shortened the interval to lambing when given around day 143 or 144 of gestation, bringing delivery forward by roughly 40 to 45 hours on average compared to untreated ewes, whereas prostaglandin alone at that stage had no effect.3The Journal of Agricultural Science. Induction of lambing: comparison of the effects of prostaglandin, oestradiol benzoate and dexamethasone The lesson: in sheep, prostaglandin is downstream of the cortisol-estrogen shift, so giving it before that shift has occurred does not reliably start labor.
Stage One: Cervical Dilation
The first stage begins with uterine contractions and cervical softening, and ends when the cervix is fully dilated. For many shepherds, the earliest clue is behavioral: the ewe separates from the flock, becomes restless, paws at the ground, lies down and gets up repeatedly, and may turn to look at her flank. These signs can be subtle, and some experienced ewes show very little external distress at all.
Internally, a great deal is happening. The cervix, which has been a firm barrier throughout pregnancy, undergoes dramatic remodeling. Collagen in the cervical tissue begins to break down, glycosaminoglycans shift in composition, and the tissue becomes progressively softer and more elastic.4Small Ruminant Research. A review of dystocia in sheep Research on dexamethasone-induced cervical changes in sheep found that measurable softening began within 12 hours of treatment and continued progressively, accompanied by a marked increase in collagen breakdown products.5Elsevier / ScienceDirect (Animal Reproduction Science). The cervix of the sheep and goat during parturition
Stage one is the longest and most variable of the three stages, commonly lasting two to six hours in ewes that have lambed before, and sometimes longer in first-time mothers. The ewe’s water bag (the fluid-filled membranes surrounding the lamb) usually appears at the vulva toward the end of this stage and may rupture on its own or during the transition into stage two.
When the Cervix Fails to Open
One of the most frustrating complications in sheep obstetrics is ringwomb, a condition in which the cervix fails to dilate fully despite otherwise normal labor. The ewe strains, contractions are present, but the cervical opening remains tight or only partially open. The underlying problem appears to involve a hormonal imbalance, particularly in the estrogen-to-progesterone ratio, that disrupts the normal production of prostaglandins within the cervical tissue itself. Without adequate prostaglandin activity, the collagen breakdown that should soften and relax the cervix simply does not progress far enough.6World’s Veterinary Journal. Diagnosis and Management of Ringwomb in Sheep: Challenges and Approaches
Ringwomb can be mild, where gentle manual dilation helps the ewe progress, or severe enough to require a caesarean section. It is worth noting that this is distinct from dystocia caused by a lamb that is too large or badly positioned; in ringwomb the problem is the cervix itself, not the lamb. The condition is unpredictable and can affect ewes of any age, though some shepherds notice it recurring in certain bloodlines.
Stage Two: Delivery of the Lamb
Stage two begins once the cervix is fully dilated and ends with the complete expulsion of the lamb. This is the stage of active, forceful abdominal straining. In a normal presentation, the lamb’s front feet appear first, followed by the nose resting on the forelegs, and then the rest of the body. The ewe may stand, lie on her side, or alternate between the two. A typical uncomplicated delivery of a single lamb takes roughly 30 minutes to an hour from the first appearance of the feet, though experienced ewes sometimes deliver in much less time.
A critical event during stage two is the stretching of the birth canal, which triggers a reflex release of oxytocin from the ewe’s brain. This surge strengthens uterine contractions and helps drive the lamb out.7animal. Maternal behaviour and lamb survival: from neuroendocrinology to practical application Research has shown that blocking the nerve signals from the vagina and cervix (using epidural anesthesia in experimental settings) eliminates both the oxytocin surge and the accompanying rise in prostaglandins, essentially stalling the process.8PubMed. Blockade of the Ferguson reflex by lumbar epidural anaesthesia in the parturient sheep: effects on oxytocin secretion and uterine venous prostaglandin F levels This reflex loop, where physical stretching drives more hormonal release which drives more contracting, is a key reason why labor tends to accelerate once the lamb enters the birth canal.
The same oxytocin release also primes maternal behavior, which is why the transition from stage two into the postpartum period is so behaviorally charged. The ewe typically begins licking and nuzzling the lamb within seconds of delivery.
Common Causes of Difficult Birth
Dystocia, or difficult birth, in sheep generally falls into a handful of categories. The lamb may be too large relative to the ewe’s pelvis. The lamb may be positioned abnormally: coming backward (breech), with a head turned back, or with one or both legs folded. The uterus may fail to contract with enough force (uterine inertia). Or, as discussed, the cervix may not dilate properly.4Small Ruminant Research. A review of dystocia in sheep
The consequences of prolonged or difficult delivery are serious. Lambs born after a difficult labor are at higher risk of being born dead or sustaining central nervous system damage from oxygen deprivation during the process. Even lambs that survive a traumatic birth are often slower to stand and nurse, which in cold weather can be fatal. Ewe body condition at mating appears to play a role: research has found that both very thin and very fat ewes at breeding are more likely to experience dystocia, with significantly higher incidence in the extremes of body condition compared to ewes in moderate condition.9Archives of Animal Breeding. Body condition status at mating affects gestation length, offspring yield and return rate in ewes
How Breed Shapes the Experience
Not all sheep have the same lambing experience, and breed plays a measurable role in how smoothly delivery goes. A comparison between South African Mutton Merino and Dormer ewes found distinct patterns: Mutton Merinos had longer parturitions and needed more assistance, with problems tending toward malpresentation and the lamb being too large for the pelvic opening. Dormers, by contrast, were more prone to uterine inertia, where contractions simply were not strong enough to push the lamb through.10Small Ruminant Research. Ease of birth relation to pelvic dimensions, litter weight and conformation of sheep In the Mutton Merinos, the pelvic dimensions of the ewe, combined with litter weight, were strong predictors of how long delivery would take.
There is active interest in breeding for easier lambing. A study of Texel ram lambs, a terminal sire breed known for muscular conformation, used CT scanning to measure pelvic and body dimensions and found that these skeletal traits are moderately to highly heritable. There were genetic hints that wider-shouldered, wider-hipped lambs tend to cause more difficulty during their own birth, and that ewes with narrower or more horizontally angled pelvises tend to have harder deliveries themselves.11Small Ruminant Research. Can genetic propensity for lambing difficulty be predicted by pelvic and body shape dimensions measured by X-ray computed tomography (CT) scanning of ram lambs? The standard errors were high, so these correlations are still being refined, but the work suggests that sire selection for pelvic shape could eventually reduce lambing difficulty in flocks that use heavily muscled terminal breeds.
Twin and Multiple Births
When a ewe carries twins or triplets, stage two essentially repeats for each lamb, with a variable interval between deliveries. The second lamb is particularly vulnerable. If the interval between the first and second lamb stretches beyond about 90 minutes, the second-born twin faces substantially higher mortality. In one study of Merino ewes, survival of second-born twins exposed to prolonged parturition (90 minutes or more between deliveries) was only about 43% in control ewes, compared to nearly 87% in ewes that had been supplemented with melatonin during the second half of pregnancy.12Oxford Academic (Journal of Animal Science). Supplementing Merino ewes with melatonin during the last half of pregnancy improves tolerance of prolonged parturition and survival of second-born twin lambs
The reasons second-born twins are at risk include partial placental separation after the first lamb is delivered (cutting off oxygen to the second), cooling of the birth canal between deliveries, and the ewe’s attention being consumed by the firstborn. For shepherds managing prolific breeds, watching for the second delivery and being ready to intervene is one of the most practical things they can do during lambing season.
Stage Three: Expulsion of the Placenta
The final stage of parturition is the passage of the fetal membranes, commonly called the afterbirth or cleansing. After the last lamb is delivered, the uterus continues to contract, gradually separating the placenta from the uterine wall at the points of attachment called placentomes. Enzymatic activity in the placentome changes from late pregnancy through delivery, and some of that enzyme activity continues even after the lambs are born, helping to break down the attachments.13PubMed. The plasminogen activator system in the ovine placentome during late gestation and stage-two of parturition
In most ewes, the placenta is passed within two to three hours of the last lamb. When it does not come away in that window, the condition is called retained fetal membranes. Observations of affected ewes in southern Greece found a recognizable progression: at first the hanging membranes were fleshy and moist with thick, congested cotyledons, but over time they dried out and became thin and stringy, the cotyledons shrank and paled, and eventually the mass dropped away on its own.14Preventive Veterinary Medicine. Incidence risk and clinical features of retention of foetal membranes in ewes in 28 flocks in southern Greece Retained membranes can predispose the ewe to uterine infection, so shepherds typically monitor for this and consult a veterinarian if the membranes have not passed within several hours.
Maternal Behavior in the Minutes After Birth
One of the more remarkable aspects of sheep parturition is the sudden behavioral transformation in the ewe. Throughout pregnancy and the estrous cycle, ewes are strongly repelled by amniotic fluid. But immediately before and after delivery, that repulsion flips to intense attraction. This switch lasts only a few hours: in most ewes, the attraction fades within about four hours of birth.15Physiology & Behavior. Attraction and repulsion by amniotic fluids and their olfactory control in the ewe around parturition The ewe vigorously licks the lamb, consuming the amniotic fluid that coats it. This licking serves multiple purposes: it clears the lamb’s airways, dries and warms the lamb, and helps the ewe learn the unique scent of her own offspring.
The attraction to amniotic fluid is driven heavily by smell. Ewes made experimentally anosmic (unable to smell) showed neither the usual repulsion during pregnancy nor the attraction at birth.16Hormones and Behavior. Perinatal visceral events and brain mechanisms involved in the development of mother–young bonding in sheep The physical stimulation of the birth canal during delivery also matters: it reduces aggression toward lambs and promotes acceptance of the newborn at the udder. In experiments with non-pregnant ewes, genital stimulation combined with the right hormonal environment was enough to induce maternal licking and allow a neonate to nurse.17Psychoneuroendocrinology. Genital, olfactory, and endocrine interactions in the development of maternal behaviour in the parturient ewe
This tight bonding window is why disturbance during and shortly after lambing can be so damaging. If a ewe is moved, frightened, or separated from her lamb during those first hours, the bonding process can fail, leading to rejection. Shepherds who have to assist a delivery or relocate a ewe typically try to ensure the lamb stays with her and that she has the opportunity to lick it thoroughly before any handling occurs.
The Lamb’s First Challenge After Delivery
From the lamb’s perspective, the transition from the uterus to the outside world is a physiological shock. The lamb goes from a warm, fluid-filled environment to air that may be well below body temperature, and must immediately begin breathing, thermoregulating, standing, and finding the udder.
Newborn lambs generate heat primarily through a specialized tissue called brown adipose tissue, which burns energy to produce warmth without shivering. Research comparing lambs born vaginally to those delivered by caesarean section found that vaginal delivery results in better activation of this heat-generating tissue. Vaginally born lambs had higher levels of key proteins in their brown fat and higher thyroid hormone concentrations, both of which support effective heat production.18PubMed. Influence of route of delivery and ambient temperature on thermoregulation in newborn lambs Caesarean-delivered lambs compensated by relying more on shivering, which is less efficient and more energy-costly. They eventually caught up in body temperature, but the initial disadvantage matters in cold conditions where every minute counts.
Ambient temperature also interacts with feeding. In lambs kept at a cool temperature (around 15°C), even a small feed was associated with a rise in body temperature, an effect that was not seen in lambs kept warm.19PubMed. Thermoregulation in newborn lambs: influence of feeding and ambient temperature on brown adipose tissue Getting colostrum into a cold lamb quickly is one of the most practical interventions a shepherd can make, both for the immune protection the colostrum provides and for the thermal boost of having something warm in the stomach.
Postpartum Recovery of the Ewe
After the placenta is passed, the ewe’s uterus begins the process of involution, shrinking back toward its non-pregnant size. The timeline varies by study and breed. In autumn-lambing Corriedale ewes, the uterus had returned to dimensions comparable to non-pregnant ewes by about day 17 after delivery.20Theriogenology. Uterine involution and ovarian changes during early post partum in autumn-lambing Corriedale ewes A separate study using ultrasound in subtropical ewes found the overall average closer to 32 days, with the most rapid shrinkage occurring between days 7 and 14, when the diameter of the previously pregnant horn dropped by more than half.21Small Ruminant Research. Factors affecting the postpartum uterine involution and luteal function of sheep in the subtropics Season, nutrition, suckling intensity, and whether the birth was difficult all influence how quickly the uterus recovers.
For flock management, the speed of uterine involution matters because it affects when the ewe can conceive again. Ewes in accelerated lambing systems, where the goal is more than one lamb crop per year, need to recover quickly. Ensuring good body condition, adequate nutrition, and freedom from uterine infection after delivery all contribute to a faster return to reproductive readiness. Ewes that experienced retained membranes or required manual intervention during delivery tend to take longer, reinforcing the value of clean, unassisted births whenever possible.