channel mutations.451 There are multiple types of monogenic autosomal dominant maturity‐onset diabetes of the young (MODY), four subtypes predominating with mutations in HNFIA (52 percent), GCK (32 percent), HNF4A (10 percent), and HNF1B (6 percent).452
A precise preconception molecular diagnosis is important so as to direct appropriate treatment. No pharmacologic treatment is indicated for the GCK‐MODY type, low dose sulfonylureas are prescribed for HNF1A‐MODY and HNF4A‐MODY, with high‐dose sulfonylureas for KATP channel‐related diabetes.451
Pregestational T1DM and T2DM are associated with poorer pregnancy outcomes, including up to a fourfold higher rate of perinatal mortality.453 The poorer glycemic control at the time of conception and the first trimester, the higher the frequency of stillbirths, congenital abnormalities, perinatal morbidity and mortality, macrosomia, dystocia in labor, and maternal mortality.454–458 Obesity, with its burden of obstetric complications and congenital anomalies457 (as discussed earlier), compounds all the problems in the diabetic mother.
Pregnant women with the chronic multifactorial autoimmune disease systemic lupus erythematosus (SLE) face a host of complications. This disorder, with its predilection for women of childbearing age, is more prevalent in non‐white populations and is characterized by involvement that includes renal, cardiovascular, musculoskeletal, neurological, rheumatological, and cutaneous systems.459 Adverse pregnancy outcomes include fetal death, preterm births, intrauterine growth restriction, and neonatal lupus.460 Women with anti‐Ro/anti‐La antibodies, the latter being specific for the diagnosis of SLE and Sjögren syndrome,461 can be asymptomatic. Anti‐Ro antibodies may precede the clinical manifestations of SLE by an average of 3.6 years.462 Note, however, these antibodies are found in up to 3 percent of the general population.463
The prime consequences of having anti‐Ro antibodies is the risk of fetal/neonatal heart block and neonatal lupus. In a study of 325 children with second‐ or third‐degree heart block, the overall mortality rate was 17.5 percent. Death in utero occurred in 6 percent.464 The risk of offspring being born with congenital heart block to a mother with anti‐Ro antibodies is between 0.2 and 2.0 percent, but 15–20 percent if there has been a previously affected fetus or neonate.464, 465 After two affected pregnancies, the subsequent pregnancy risk is 50 percent.466 Complex therapeutic considerations include fluorinated glucocorticoids (dexamethasome and betamethasome) and maternal fetal echocardiography monitoring.467, 468 Neonatal lupus with congenital heart block will usually require pacemaker implantation.469, 470 For mothers with a previous affected pregnancy, hydroxychloroquine has been recommended as a pre‐emptive treatment.471, 472 Fortunately, only a third of mothers carrying fetuses with complete heart block have an identified autoimmune disorder such as lupus or Sjögren disease.473
Certain genetic disorders may threaten maternal and fetal health in pregnancy and are discussed in detail in Chapter 31.
A history of infertility
Beyond the issues of paternal age discussed earlier, there is the evidence that structural chromosomal abnormalities, which occur in 0.25 percent of births, more frequently have their origin in paternal chromosomes. In a 2006 report, 72 percent of de novo unbalanced chromosomal rearrangements were of paternal origin.474 The likelihood of having a translocation doubled every 10 years after the age of 25.475 An American Cancer Society Study of 2,532 cases of hematological cancers noted that men over 35 had a 63 percent higher risk of having affected offspring when compared with those under 25.476 A small, but statistically significant increased risk of nonchromosomal congenital malformations associated with advanced paternal age was reported by the National Birth Defects Prevention Study.477 Malformations included were cleft lip, diaphragmatic hernia, right ventricular outflow tract obstruction, and pulmonary stenosis.
About 10 percent of couples have infertility. A World Health Organization multicenter study concluded that the problem appeared predominantly in males in 20 percent of cases, predominantly in females in 38 percent, and in both partners in 27 percent. In the remaining 15 percent of cases, no definitive cause for the infertility was identified.478 Care should be exercised in the preconception counseling of a couple with a history of infertility. In the absence of a recognizable cause, karyotyping of both is recommended. Unrecognized spontaneous abortions may have occurred without the patient's awareness, caused by overt structural chromosome rearrangements or microdeletions or duplications (see Chapters 11 and 13). Microarrays performed after routine cytogenetics on products of conception in 2,389 cases revealed significant copy number changes or whole‐genome uniparental disomy in 1.6 percent and 0.4 percent of cases, respectively.479 A study of 1,300 infertile men revealed chromosomal abnormalities in 10.6 percent and Y‐microdeletions in 4.0 percent.480 Recognized habitual abortion due to the same causes would also require cytogenetic analysis. Such studies may reveal a parent (rarely both) with a chromosomal rearrangement with significant risks for bearing a child with intellectual disability and/or malformations, who could benefit from prenatal or preimplantation diagnosis.
Other examples of disorders characteristically associated with recurrent pregnancy loss or infertility include premature ovarian failure in fragile X syndrome carriers (see Chapter 16), and the X‐linked disorders steroid sulfatase deficiency481 and incontinentia pigmenti.482 Thrombophilia as a significant cause remains uncertain.483, 484 In about 8 percent of women experiencing recurrent abortion a mutation in the SYCP3 gene (which encodes an essential component of the synaptonemal complex, key to the interaction between homologous chromosomes) was noted.485 An extensive list of genes related to premature ovarian failure have been recognized,486 especially noteworthy in a highly consanguineous population.487 Consequently, next‐generation sequencing488 or whole‐exome sequencing,489–492 cost issues aside, would be indicated.
Although the investigation to determine the cause of male or female infertility can be extensive, several observations are pertinent here. We recognized that congenital bilateral absence of the vas deferens (CBAVD),493 which occurs in 1–2 percent of infertile males, is primarily a genital form of CF (see Chapter 15). Men with CBAVD494 should have CF gene analysis (sequencing, poly T variant analysis, deletion analysis). A meta‐analysis concluded that among CBAVD patients, 78 percent had one recognizable CFTR gene mutation whereas 46 percent were noted to have two mutations.495 The mutation detection rate is likely to exceed 92 percent including large gene rearrangements.496 Of interest is the observation of Traystman et al.497 that CF carriers may be at higher risk for infertility than the population at large. Men who test negative for a CFTR mutation should have the ADGRG2 gene on the X chromosome sequenced.498, 499
Some patients with CBAVD (21 percent in one study500) also have renal malformations. These patients may have a normal sweat test and thus far no recognizable mutations in the CF gene.500, 501 Renal ultrasound studies are recommended in all patients with CBAVD who have normal CFTR analyses. The partner of a male with CBAVD and a recognized mutation(s), after gene analysis, should routinely be offered sequencing and deletion analysis of the CFTR gene. Such couples frequently consider epididymal sperm aspiration,502, 503 with pregnancy induced by IVF. Precise prenatal and/or preimplantation genetic testing
