Sites of implantation of embryoand

pregnancy with placental abnormalities

Sites of implantation of embryo

introductionImplantation begins first with attachment (adplantation) of the blastocyst through the outer trophblast cells to the uterine lining. Following adplantation, trophoblastic cells on the outside differentiate into syncitiotrophoblasts which invade the uterine endometrium. The blastocyst then moves into the endometrium, initially partially buried, and on completion of implantation, is fully buried in the endometrium. The site of implantation is marked on the surface by a "plug".

Normal pregnancy

Normal site of implantation

the blastocyst makes contact with the lining of the uterus - the endometrium. This has prepared for such a possibility by thickening, becoming more glandular, and developing a rich blood supply. The blastocyst begins to implant, a process that will take several days

Abnormal Implantations in uterus

Placenta praevia : the placenta is attached to the uterine wall close to or covering the cervix.It causes difficulty during childbirth and may cause severe bleeding.Various types of placenta praevia may be recognized as given below:1. Type I or low lying: The placenta sits in the lower segment of

the uterus but does not touch the cervix2. Type II or marginal: The placenta touches, but does not cover,

the top of the cervix.3. Type III or partial: The placenta partially covers the top of the

cervix4. Type IV or complete: The placenta completely covers the top of

the cervix (placenta preavia)

Placenta acceta, increta, percreta

• Placenta accreta– Accounts for 75-78%– Placenta attached directly to

the muscles of the uterine wall

• Placenta increta– Accounts for 17% of cases– Placenta extends into the

uterine muscles

• Placenta percreta– 5-7% which extends through

the entire wall of the uterus

Implantation outside the uterus

Tubal pregnancy Ectopic pregnancy

• often occurs if zona pellucida is lost too early allowing premature implantation

Tubal pregnancy 94%• embryo may develop through early

stages.• can erode through the uterine horn• reattach within the peritoneal cavity

• Most common sites of ectopic pregnancy

1. external surface of uterus2. bowel3. gastrointestinal tract, mesentry4. peritoneal wall

• If not spontaneous then, embryo has to be removed surgically

Tubal pregnancy after hesterectomy

Ectopic pregnancy

An ectopic pregnancy, or eccysis, is a complication of pregnancy in which the embryo implants outside the uterine cavity. With rare exceptions, ectopic pregnancies are not viable. Furthermore, they are dangerous for the parent, since internal haemorrhage is a life threatening complication. Most ectopic pregnancies occur in the Fallopian tube (so-called tubal pregnancies), but implantation can also occur in the cervix, ovaries, and abdomen. In a typical ectopic pregnancy, the embryo adheres to the lining of the fallopian tube and burrows into the tubal lining. Most commonly this invades vessels and will cause bleeding.

Ectopic pregnancy

Ectopic pregnancies can be classified into 4 categories

1. Tubal pregnancy2. Non-tubal ectopic pregnancy3. Heterotopic pregnancy4. Persistent ectopic pregnancy

Tubal pregnancyThe vast majority of ectopic pregnancies implant in the Fallopian tube. Pregnancies can grow in the • fimbrial end (5%),• ampullary section (80%),• isthmus (12%), • cornual and interstitial part

of the tube (2%). 7 week embryo in open oviduct

Non tubal pregnancyTwo per cent of ectopic pregnancies occur are intraabdominal. Very rarely, a live baby has been delivered from an abdominal pregnancy. In such a situation the placenta sits on the intraabdominal organs or the peritoneum and has found sufficient blood supply. This is generally bowel or mesentery, but other sites, such as the (kidney), liver or hepatic artery or even aorta have been seen. Any attempts to remove the placenta from the organs to which it is attached usually lead to uncontrollable bleeding from the attachment site.

Interstitial pregnancy

An interstitial pregnancy is a uterine but ectopic pregnancy; the pregnancy is located in that part of the Fallopian tube that penetrates the muscular layer of the uterus. Interstitial pregnancies account for 2–4% of all tubal pregnancies. About one in fifty women with an interstitial pregnancy die. Patients with an interstitial pregnancies have a 7-times higher mortality than those with ectopics in general. With the growing use of assisted reproductive technologies, the incidence of interstitial pregnancy is rising

Persistent ectopic pregnancyA persistent ectopic pregnancy refers to the continuation of trophoblastic growth after a surgical intervention to remove an ectopic pregnancy. After a conservative procedure that attempts to preserve the affected fallopian tube such as a salpingotomy, in about 15-20% the major portion of the ectopic growth may have been removed, but some trophoblastic tissue, perhaps deeply embedded, has escaped removal and continues to grow

Patients with an ectopic pregnancy are generally at higher risk for a recurrence, however, there are no specific data for patients with an interstitial pregnancy. When a new pregnancy is diagnosed it is important to monitor the pregnancy by transvaginal solography to assure that is it properly located, and that the surgically repaired area remains intact. Caesarean delivery is recommended to avoid uterine rupture during labour.

Placental abnormalities

Placentaintroduction

• A placenta is an organ that connects the developing foetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply

• Normal placenta- diameter = 22cm thickness = (2.0~2.5)cm

PLACENTAL ABNORMALITIES

Abnormalities of placenta can be classified into three broad categories;• Abnormal shape • Abnormal implantation• Degenerative placental lesions

Abnormalities based on shape and

implantation Placenta bipartita or bilobata

the placenta is separated into lobes. division is incomplete and the vessels of foetal origin extend from one lobe to the other before uniting to form the umbilical cord

Placenta duplex, triplex two or three distinct lobes are visible entirely and the vessels remain distinct.

Succenturiate lobessmall accessory lobe ≥1, develop in the membranes at a distant from the periphery of the main placenta, to which they usually have vascular connections of foetal origin incidence : 5%

retained in the uterus after delivery and may cause serious haemorrhage accompanying vasa previa - dangerous foetal haemorrhage at delivery

Membranaceous Placenta

all of the foetal membranes arecovered by functioning villi and the placenta develops as a thin membranous structure occupying the entire periphery of the chorion

serious haemorrhage d/t associated placenta previa or accreta

Abnormality Definition Clinical significance

Extrachorial Pla-centation

Circumvallate Placenta

Circummarginate placenta

When the chorionic plate, which is on the fetal side of the placenta, is smaller than the basal plate, which is located on the maternal side, the placental periphery is uncovered

Fetal surface of such a placenta presents a central depression surrounded by a thickened, grayish-white ring. Ring : composed of a double fold of amnion and chorion with degenerated decidua and fibrin in between Within the ring, the fetal surface presents the usual appearance, except that the large vessels terminate abruptly at the margin of the ring

Ring does not have the central depression with the fold of membranes

Antepartum hemorrhage - from placental abruption and fetal hemorrhage Preterm delivery Perinatal mortality Fetal malformations less well defined

Abnormalities based on degenerative lesions

• Causes• : trophoblast aging or impairment of uteroplacental circulation with infarction • Deposition of calcium salts is heaviest on the maternal surface in

the basal plate. → further deposition occurs along the septa and both increase as pregnancy progresses• Calcification : 10 - 15% of all placentas at term some degree of calcification ≥ ½ of placentas

Calcified placentaA. Specimen of a calcified(white

regions) placentaB. Sonography of another calcified

placenta

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