Multiple Pregnacies

IVF

While multiple gestation (2%–3% of births) is rising due to __ it remains a pregnancy complication because of the physical strain on the mother.

higher levels of Follicle-Stimulating Hormone (FSH)

As women approach perimenopause (30s–40s), the brain releases __ to compensate for decreasing ovarian efficiency.

Multiple eggs

ADVANCED MATERNAL AGE

Due to the rise of FSH this can overstimulate the ovaries, causing them to release __ and increasing the likelihood of fraternal twins

hormonal shifts and changes in ovarian sensitivity or the uterine environment after a body has already carried a pregnancy to term

The statistical likelihood of having twins increases with each subsequent pregnancy. This is likely due to __

IVF Multiples

clinicians often transfer multiple embryos into the uterus to improve the odds of a successful pregnancy. If more than one embryo successfully implants, it results in a multiple gestation.

Identical (Monozygotic) and Fraternal (Dizygotic)

Types of Twinning

Identical (Monozygotic)

single zygote (one egg + one sperm) divides into two individuals. They share the same DNA and sex. Typically, they have one placenta and one chorion, but two amnions and two cords.

Identical (Monozygotic)

PCAA

Fraternal (Dizygotic)

Two separate eggs are fertilized by two separate sperm. They are essentially siblings born at the same time and can be the same or different sexes. They always have two placentas, two chorions, and two amnions.

Dichorionic-Diamoniotic

Two enbryos developed completely independent EARLY SPLIT (DAY 0-3)
2 Placenta (food/oxygen) 2 chorions outer protective membrane, 2 amnions inner fluid— filled bubble

Monochorionic-Diamnotic

Single fertilized egg begins to develop, split happens after outer layer (chorion) has already started to form two embryos.

Trapped inside the same outer shell

1 shared Placenta, 1 shared chorion, 2 amnions

Monochorionic- Monoamniotic

Fertlized eggs has already implanted

Begun forming structures before dividing intro two individuals
Later split outer sac (chorion) & inner sac (amnion) formed single units

1 shared placenta, shared chorion, 1 shared amnion

DiDi (2 Placentas, 2 Sacs)

Days 0–3 Split

MoDi (1 Placenta, 2 Sacs)

Days 4–8 Split

MoMo (1 Placenta, 1 Sac)

Days 8–13 Split

Conjoined Twins (Incomplete Split)

After Day 13 SPlit

Conjoined Twins

The split occurs very late—usually 13 to 15 days after fertilization. By this point, the embryonic disc has already begun to differentiate into specific body structures, so the separation is incomplete.

Throracopagus

Joined at the chest (often sharing a heart)

Omphalopagus

Joined at the abdomen (often sharing a liver)

Craniopagus

Joined at the skull/head

Pygopagus

Joined at the base of the spine/buttocks

uterus grows faster than expected

PHYSICAL SIGNS of Multiple Pregnancy

• volume of the fetuses, placentas, and amniotic fluid forces the uterus to expand more rapidly than a singleton pregnancy

There is Quickening or Flurries in multiple areas of the abdomen

FETAL ACTIVITY OF Multiple Pregnancies

Because fetuses are positioned differently, their limbs strike different abdominal walls

Why is flurries in multiple abdominal areas rather than one localized spot.

Elevated Alphafetoprotein and multiple FHT via auscultation

CLINICAL FINDINGS of Multiple Pregnancy

Early ultrasound

IMAGING in multiple pregnancies

Dichorionic Diamniotic (DiDi) Twins

Usually delivered at 37–38 weeks.

Monochorionic Diamniotic (MoDi) Twins:

Usually delivered at 36–37 weeks

Monoamniotic (MoMo) Twins

High risk (sharing one sac); delivery is usually via C-section at 32–34 weeks.

Vaginal Birth

MODE OF DELIVERY

Often possible for twins if the first baby (Twin A) is head-down (cephalic) and there are no other complications.

Cesarean Section

MODE OF DELIVERY

Recommended for triplets or higher-order multiples, or if Twin A is breech

massive amounts of hormones

With multiple placentas or one large one, the body produces

Pregnancy-Induced Hypertension (PIH) and Hydramnios

If the body produces massive amounts of hormones it could lead to

Preterm labor

The stretching triggers early contractions which can lead to

Postpartum hemorrhage

After birth, the "over-stretched" uterine muscle is often too tired to contract down quickly, leading to __

• velamentous cord insertion

• placenta previa

Why cord & Placenta issues occur

Velamentous Cord Insertion

In a crowded uterus, the umbilical cord may not attach to the center of the placenta. Instead, it attaches to the fetal membranes. Because these vessels aren't protected by the usual "Wharton's Jelly," they are easily torn or compressed during labor.

Placenta Previa

With two placentas (or one very large one), there is more "surface area" covered. This increases the mathematical chance that the placenta will grow over the internal os (cervical opening).

Twin-to-Twin Transfusion

This happens only in Monochorionic (shared placenta) twins:

Vascular Anastomoses

Deep inside the shared placenta, the blood vessels of the two twins connect.

Imbalance of TTTS

Blood begins to flow more in one direction than the other.

Donor Twin

Becomes dehydrated, produces less urine (low amniotic fluid), and has stunted growth (undergrowth

Recipient Twin

Gets too much blood, which overloads their heart and kidneys, leading to excess urine (high amniotic fluid) and overgrowth

Cord Entanglement

In a Monoamniotic pregnancy, there is no "room divider" (amnion). As the twins move and flip, their umbilical cords can literally braid or knot together. This can cut off oxygen and nutrients to one or both babies