• Is a pregnancy in which more than
one fetus is present. the fetuses may
arise from one or more zygotes and
are usually separate but may rarely
Multiples make up only about 3 in 100 births, but the multiple
birth rate is rising
Hellin’s Law is the principle that one in about 89 natural
pregnancies ends in the birth of twins, triplets once in 892
births, and quadruplets once in 893 births-probability; namely
n’lets once in 89n−1.
High levels of beta-HCG and MSAFP and hyperemesis gravidarum.
Abdominal palpation shows multiple small parts and multiple large poles.
Fundal level is more than GA
In auscultation, many fetal heart sounds (sometimes gallop rhythm).
Abdominal or transvaginal U/S show many heads.
During labor, the presenting part is small in relation to the size of the uterus.
Dizygotic twins (non-identical/ Fraternal)
Occur from ovulation and subsequent
fertilization of two oocytes. This results in
dichorionic diamniotic twins, where each
fetus has its own placenta and amniotic
cavity. Although they always have two
functionally separate placentae
(dichorionic),if the two ova implanted close to
each other, the placentae can become
anatomically fused together and appear to
the naked eye as a single placental mass.
They always have separated amniotic cavities
(diamniotic) and the two cavities are
separated by a thick three-layer membrane
(fused amnion in the middle with chorion on
either side). The fetuses can be either same-
sex or different-sex pairings. (the similarity
between them is like the similarity between
any two members of the same family).
Dichorionic diamniotic. If the zygote splits shortly after fertilization (within 3
days after fertilization, morula stage), the twins will
each have a separate placenta
Monochorionic diamniotic (20%) division of the zygote occurs between days four and
eight postfertilization (at blastocyst stage). The vast
majority of monochorionic twins have two amniotic
cavities (diamniotic) but the dividing membrane is thin,
as it consists of a single layer of amnion alone.
Monochorionic monoamniotic (1%) when division occurs between days 8 and 12
postfertilization (splitting of the embryonic disk).
Conjugated twins when incomplete division of the fertilized ovum, occur
after more than 13 days of fertilization (embryo stage).
Risk factors 14
Dizygotic twins Monozygotic twin
Previous multiple pregnancies ( the strongest)
No identifiable risk factors
Race ( more in blacks than whites)
Family history from mother’s side only and with spontaneous
multiple gestation only (IVF is not included).
Assisted reproductive technologies like IVF.
Risk of twinning is up to 10% with drugs like clomiphene citrate and
up to 30% with human menopausal gonadotropin
Increased maternal age, parity, height and weight due to higher
levels of FSH
BY CLINICAL FEATURES (HISTORY
AND PHYSICAL EXAM).
DEFINITIVE DIAGNOSIS BY U/S.
“WOMEN WITH MULTIPLE
PREGNANCIES SHOULD BE
OFFERED AN ULTRASOUND SCAN
AT AROUND 11 TO 14WEEKS”
• Twin pregnancy is associated with higher rates of almost
every potential complication of singleton pregnancy, with
the exceptions of postterm pregnancy and macrosomia,
and is also associated with some unique complications
Give mother iron and folate supplementation to prevent anemia, monitor BP to
detect preeclampsia, educate mother regarding preterm labor symptoms and
signs, and perform serial ultrasound examinations looking for twin–twin
transfusion (amniotic fluid discordance).
Intrapartum Route of delivery is based on presentation in labor—vaginal delivery if both are
cephalic presentation (50%); cesarean delivery if first twin in noncephalic
presentation; route of delivery is controversial if first twin is cephalic, and
second twin is noncephalic, but if they are stable and have the same way,
vaginal delivery is indicated.
Postpartum: Watch for postpartum hemorrhage from uterine atony owing to an
When to deliver when CS is indicated?
37 to 38 weeks Dichorionic
36 weeks Monochorionic
35 weeks Uncomplicated Triplet
32 to 33 weeks Monochorionic Monoamniotic
28 weeks Quadruplet
• Develops in 15% of mono-di twins with 25% mortality rate.
• Most common cause of oligohydramnios and polyhydramnios in twins.
• The twins share a single placenta but do so unequally, because there is
an anastomoses between the two fetal circulations that could be artery
to artery, artery to vein (most severe), vein to vein.
• The donor twin gets less blood supply, resulting in growth restriction,
oligohydramnios, hypotension, anemia and even fetal death due to heart failure
resulted from anemia. However, neonatal outcome is usually better.
• The recipient twin gets more blood supply, resulting in excessive growth,
hypertension, polyhydramnios, polycythemia and fetal death due to congestive heart
failure due to overperfusion.
• Diagnosis by doppler U/S showing anastomosis within the placenta.
• Intrauterine fetal surgery is indicated to laser the vascular connections on the
placental surface between the two fetuses. Neonatal course is often complicated.
Stage 1 Oligohydramnios and polyhydramnios sequence and the bladder of the donor twin is
visible. Dopplers in both twins are normal.
Stage 2 Oligohydramnios and polyhydramnios sequence, but the bladder of the donor is not
visualized. Dopplers in both twins are normal.
Oligohydramnios and polyhydramnios sequence, non-visualized bladder and abnormal
Dopplers. There is absent/reversed end-diastolic velocity in the umbilical artery,
reversed flow in a-wave of the DV or pulsatile flow in the umbilical vein in either fetus.
Stage 4 One or both fetuses show signs of hydrops.
Stage 5 One or both fetuses have died.
• It is a classical complication of a
pregnancy which can mean either
one or more loops of the umbilical
cord encircling any part of the fetal
body or two umbilical cords becoming
entangled with each other.
Locked Twin Syndrome
• Locked twins usually occur when the
after-coming head of the first breech
fetus is locked with the head of the
second cephalic fetus. Of the different
etiological factors, the most important
are the ageand parity of the mother
and the size of the twins
• Kenny, L. C., & Bickerstaff, H. (2016).
Gynaecology by Ten teachers. CRC Press.
• Sakala, E. P. (2020). Usmle Step 2 Ck lecture
notes 2021 Obstetrics and Gynecology. Kaplan