Table 8-1. Complications of Twin Pregnancies
| Anemia ↑ 3x (iron & folate) | ||
| ANTEpartum | Preeclampsia ↑ 3x | |
| Gestational diabetes ↑ 2x | ||
| Thromboembolism ↑ 4x | ||
| Preterm labor (50%) | ||
| INTRApartum | ||
| Malpresentation (50%) | ||
| Cesarean delivery (50%) | ||
| POSTpartum | Hemorrhage ↑ 5x | |
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Dizygotic twins arise from multiple ovulation with2 zygotes. They are always dichorionic,diamnionic.
Monozygotic twins arise from one zygote. Chorionicity and amnionicity vary according to theduration of time from fertilization to cleavage.
• Up to 72 hours (separation up to the morula stage), the twins are dichorionic, diam-nionic. There are 2 placentas and 2 sacs. This is the lowest risk of all monozygotictwins.
• Between 4 and 8 days (separation at the blastocyst stage), the twins are monochori-onic, diamnionic. There is 1 placenta and 2 sacs. A specific additional complication is twin–twin transfusion, which develops in 15% of mono-di twins. The twins share a
single placenta but do so unequally. The donor twin gets less blood supply, resulting in growth restriction, oligohydramnios, and anemia. However, neonatal outcome is usu-
ally better. The recipient twin gets more blood supply, resulting in excessive growth, polyhydramnios, and polycythemia. Intrauterine fetal surgery is indicated to laser thevascular connections on the placental surface between the 2 fetuses. Neonatal course is often complicated.
Medical Education Division of the Brookside Associates, brooksidepress.org
Figure I-8-1. Monochorionic, Diamniotic Twin Gestation
• Between 9 and 12 days (splitting of the embryonic disk), the twins are monochori-onic, monoamnionic. There is only 1 placenta and 1 sac. Specific additional risks aretwin–twin transfusion but particularly umbilical cord entanglement which can result in fetal death. This is the highest risk of all monozygotic twins.
• After 12 days, conjoined twins result. Most often this condition is lethal.
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Table 8-2. Postconception Days to Identical Twin Cleavage
| Dichorionic–diamnionic | 0–3 days |
| Morula | |
| Monochorionic–diamnionic | 4–8 days |
| Blastocyst | |
| Monochorionic–monoamnionic | 9–12 days |
| Embryonic disk | |
| Conjoined | >12 days |
| Embryo | |
Clinical Findings. Hyperemesis gravidarum is more common from high levels ofb-hCG.
Uterus is larger than dates. Maternal serum a-fetoprotein is excessively higher than with one fetus.
Management
• Antepartum: Give mother iron and folate supplementation to prevent anemia, moni-tor blood pressure 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 deliveryif 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.
• Postpartum: Watch for postpartum hemorrhage from uterine atony owing to an over-distended uterus.
ALLOIMMUNIZATION
A 32-year-old woman, G2 P1, was seen for her first prenatal visit at 12 weeks’ gestation. Her prenatal laboratory panel reveals a blood type of O negative. Her atypical antibody screen (indirect Coombs test) is positive. She has been married to the same husband for 10 years and states he is the father of both her pregnancies.
She did not receive RhoGAM during her last pregnancy.
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Definition. A pregnant woman has developed antibodies to foreign red blood cells (RBCs),most commonly against those of her current or previous fetus(es), but also caused by transfu-sion of mismatched blood.
Pathophysiology
• The most common RBC antigens are of the Rh system (C, c, D, E, e), with the most common being big D.
• Antibodies to RBC antigens are detected by indirect Coombs test (atypical antibody test [ATT]). The concentration of antibodies is reported in dilutional titers with the lowest level being 1:1, and titers increasing by doubling (e.g., 1:1, 1:2, 1:4, 1:8, 1:16, 1:32…1:1,024, etc.).
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• Hemolytic disease of the newborn (HDN) is a continuum ranging from hyperbili-rubinemia to erythroblastosis fetalis. HDN is caused by maternal antibodies crossing into the fetal circulation and targeting antigen-positive fetal RBCs, resulting in hemo-lysis. When severe, this can result in anemia, fetal hydrops, and even death.
Risk Factors. Alloimmunization most commonly occurs when fetal RBCs enter the mother’scirculation transplacentally at delivery. It can also occur if a woman is transfused with mis-matched RBCs. Other pregnancy-related risk factors are amniocentesis, ectopic pregnancy, D&C, abruptio placenta, and placenta previa.
Protective Factors. ABO incompatibility decreases the risk of maternal alloimmunizationfrom foreign RBCs. Naturally occurring anti-A and anti-B antibodies rapidly lyse foreign RBCs before maternal lymphocytes are stimulated to produce active antibodies.
Requirements (all must be present).
• Mother must be antigen negative.
• Fetus must be antigen positive, which means the father of the pregnancy must also be antigen positive.
• Adequate fetal RBCs must cross over into the maternal circulation to stimulate her lymphocytes to produce antibodies to the fetal RBC antigens.
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• Antibodies must be associated with HDN.
• A significant titer of maternal antibodies must be present to cross over into the fetal circulation and lead to fetal RBC hemolysis.
Zone 3
High anemia risk
| m) | Intrauterine | ||||||||
| h | transfusion | Deliver | |||||||
| 450 | Zone 2 | ||||||||
| OD | Mod anemia risk | ||||||||
| (D | Repeat | ||||||||
| bilirubin | |||||||||
| in 1 | week | ||||||||
| Repeat | |||||||||
| fluid | |||||||||
| in 2 | weeks | ||||||||
| Amniotic | |||||||||
| Zone 1 | Repeat | in 3 | weeks | ||||||
| No or mild anemia risk | |||||||||
| 19 | 22 | 25 | 28 | 31 | 34 | 37 | 40 | ||
| Gestational age in weeks | |||||||||
Figure I-8-2. Liley Graph
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Management.
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