Which is the ideal age for motherhood?

Studies show that women are delaying motherhood more and more, and yet, only a few know about the health risks that come with it.

The questions were inevitable: family and friends started wondering when Miriam* was going to have a baby as soon as she hit 30. She is a pilot and at the time, she would be away for work for five to six weeks at a time. She was also working towards becoming a captain, which, as soon as she attained the position, required a few years of proving herself, solidifying the position.

In 2009, Miriam was involved in a plane accident and during the six-month recovery period, she had time to think and realised she was missing out on motherhood. She was 33-years-old then. Apart from her demanding job, she and her partner worked in separate towns. She changed jobs so she could 'settle down' and moved to Nairobi to join her partner. She doesn't fly actively anymore.

They started trying for a baby, and after a year with no positive results, decided to see a fertility specialist. Miriam first went through a hysterosalpingogram (or HSG), a test that detects blockages in the fallopian tubes and abnormalities in the uterus, both of which can prevent pregnancy. There were no physical problems detected. The doctor prescribed drugs that would regulate ovulation. Because her job required frequent travel and being away from home for weeks at a time, she wasn't able to take the drugs.

In October 2015, when she was 39-years-old, she found out that she was pregnant. Unfortunately in December that year, she suffered a miscarriage. "After that I wasn't in the right frame of mind to start trying again," says Miriam. In fact, she stopped thinking about it altogether. Regular exercise helped get her out of the funk. "I started doing a lot of exercise, lots of boot camp and the good thing about exercise is, apart from helping you in keeping fit, it helps clear your mind. Before that, all I thought about was trying to have a baby. With exercise I got peace of mind. My thinking changed from desperately wanting a baby to 'If I get pregnant, well and good. If I don't, so be it.'"

She went back to the doctor's in May last year for the next course of action. After a blood test revealed again that there was nothing physically wrong with her, the doctor suggested assisted reproductive technology. Before deciding what to do next, Miriam took a vacation and while away, she missed her periods. A test for pregnancy turned out positive. She had, she says, the usual nerves every expectant woman suffers, but that increased following routine questions by a radiologist who asked how old she was if that would be her first childbirth and whether she had done genetic testing (she hadn't). She had just hit 40.

"Naturally, I was worried when he brought up chromosomal abnormalities and how the risk goes up in older women," Miriam says. The screenings revealed a healthy foetus. The pregnancy went smoothly, "even smoother than those of my younger friends. I didn't have any adverse reactions to food, I didn't experience any nausea. I only had heartburns when I was nine months," she says.

She describes herself as a "laid back mother and more chilled out than I would have been if I had had the baby earlier." And because she is much better off now financially and mentally, "my partner and I worry less and enjoy the baby more, even though the sleepless nights are killing us," laughs Miriam, who requested that we don't use her real name to protect her privacy and that of her partner. Her last statement isn't surprising given the growing body of research that shows that older mothers are better, less worried mothers.

OLDER MOTHERS ARE BETTER, LESS WORRIED MOTHERS

In the most recent study, researchers from Aarhus University School of Business and Social Sciences found that older mothers are less likely to punish and scold their children while raising them, and that the children have fewer behavioural, social and emotional difficulties. This is as a result of psychological maturity attained with age. "We know that people become more mentally flexible with age, are more tolerant of other people and thrive better emotionally themselves. That's why psychological maturity may explain why older mothers do not scold and physically discipline their children as much," Professor Dion Sommer, one of the researchers of the study, said.

Sociology professor Grace Wamue-Ngare of the Department of Gender and Development Studies at Kenyatta University says that women are increasingly having their first baby later in life because of factors such as education and career advancements, improved contraception and high living costs.

But while women are attaining psychological well-being with age on one hand, biology is playing against them on the other. When Janet Jackson announced her pregnancy last year at age 50, comments on social media feeds varied from congratulatory messages to questions whether pregnancy at 50 is healthy. Medical experts have warned about the risk factors associated with advanced maternal age, that is, when a woman is 35 or older whether the childbirth is the first or not. While the factors that determine when a woman should get pregnant range from one individual to the other, or as one doctor I interviewed succinctly put it, "none of our business," where the health of the mother and the baby are concerned, age does matter.

BEST AGE FOR MOTHERHOOD

"As far as health is concerned, 24 to 30 is the best age to get pregnant because a woman is at the peak of fertility. Too early or too late carries risks of complications," says Dr Joe Wanyoike Gichuhi, a senior lecturer in the Department of Obstetrics and Gynaecology at the University of Nairobi. As age increases, he says, so does the risk of other problems that may affect fertility such as uterine fibroids, adenomyosis and endometriosis.

The biggest risk an older women faces, though, is difficulty conceiving because of the sharp decline of fertility at 35. "A woman is born with a certain number of eggs which naturally age and die off, a process called atresia. The eggs are at their highest at 16 weeks in the female foetus, about six million. At childbirth that number has gone down to about half. By the time a woman is hitting puberty, the number has gone down further still. That's the main cause of difficulty conceiving as a woman grows older," says Dr Wanjiru Ndegwa-Njuguna, a fertility specialist at Footsteps to Fertility Centre. "If you're over 35 and haven't been able to conceive within six months of regular intercourse then it is advisable that you see a doctor," she says. If, on the other hand, you're below 35 and haven't conceived within a year of regular intercourse, see a doctor.

I ask Peter Gichangi, an associate professor of human anatomy at the University of Nairobi, why atresia is gradual over time but rapid once a woman turns 35 and he explains that when a woman gets closer to menopause - which on average occurs between 45 and 55 years of age - the decline is much faster and that is genetically programmed so a woman doesn't make a baby when they've hit menopause. "It is a natural way of reducing the possibility of pregnancy during menopause," he says. "Ageing affects both men and women," he adds, "the difference is for a woman, once she has hit menopause, her chances of naturally having a baby end at that point. Men produce sperm throughout their lives. A man has a potential to make a baby as long as he is alive. The sperms are probably fewer and of poor quality but still there."

Professor Gichangi explains that risks of complications such as gestational diabetes, hypertension, spontaneous abortion (or miscarriage), premature delivery, low birth weight, stillbirth and chromosomal abnormalities increase with advanced maternal age. High-risk infants (preterm, low birth weight, multiple gestations such as twins) may continue to have health problems after hospital discharge and higher rates of hospitalisations than full-term peers, shows a study in the Journal of Pediatrics.

The biological mechanisms behind this are uncertain but experts say that it may be related to a poor uterine vascular system, and in the case of stillbirth, the association between older age and certain risk factors such as chronic diseases and medical or obstetric complications may also play a role, shows a study in the Canadian Medical Association Journal.

CHROMOSOMAL ABNORMALITIES

The most common chromosomal abnormalities associated with advanced maternal age, explains Anup Devani, a molecular biologist and laboratory director at GeneMetrics, are Down syndrome, a condition that is associated with intellectual disability and distinct physical features, Edwards syndrome, associated with severe disabilities and Patau syndrome, associated with multiple and complex organ defects.

"They are generally called trisomies. A trisomy literally means three chromosomes," Devani says. A normal cell has 46 chromosomes: 22 pairs of autosomes and one pair of sex chromosomes, XX for a girl and XY for a boy. "In Down syndrome there are three copies of chromosome 21 which is quite small. In Edward syndrome there are three copies of chromosome 18 which is a little bigger and in Patau syndrome three copies of chromosome 13 which is even bigger. We number them 1 to 22, one being the biggest and 22 the smallest. The larger the chromosome is, the more genes there are on it. Chromosome 21 is quite small so the likelihood of a child with three copies of it surviving is higher because there are less genes that are damaged or incorrectly expressed. And obviously if you go to chromosome 18 which is bigger there's more likely for things to go wrong and with chromosome 13 even bigger still."

There are a lot of theories that explain the relationship between advanced maternal age and the risk of chromosomal abnormalities: one is the concept of cell senescence (the state of being old or the process of becoming old) which, professor Gichangi explains, affects cell division.

How does an older woman know for sure whether the baby she is carrying is free of mentioned defects? "We need to remember that these conditions are not guaranteed, the fact that there is an increased risk means just that - there is an increased risk," explains Devani. "But to be entirely certain of that fact, genetic testing is the right way to go."

Dr Nelson Kimani, a consultant radiologist at Kenyatta National Hospital, says that while some of the features of these conditions can be picked up by ultrasound, the tests are merely indicative - it is not as precise as genetic testing. The idea of these genetic tests, because abortion is illegal in Kenya unless the mother's life is in danger, is at least you're informed well in advance. That way you have plenty of time to get your head around it and understand what it is that you're going to have to deal with.

A NUMBERS GAME

These conditions are usually as a result of a less than perfect egg cell and that, the argument goes, is down to a numbers game. Each day, a man can make millions of sperm. The chances of a faulty sperm cell being able to fertilise an egg are less because they have some kind of disadvantage in the race to the egg. A woman, though, normally releases one egg to be fertilised during ovulation.

Studies show that women are not fully aware of the health risks associated with delayed childbirth. For example, in a study sampling American women in the journal Human Reproduction by researchers from the University of California, participants were "shocked" to discover that fertility rapidly declines after 35. They imagined that the decline starts at 40 while others imagined the decline is gradual at around the age of menopause.

Another assumption in the general population is that Assisted Reproductive Technologies can fully compensate for infertility, as demonstrated by a study in the Human Reproduction Update. Assisted Reproductive Technologies such as in vitro fertilization cannot fully compensate, the report reads, further stating that the success rates of these techniques sharply decrease with age.

Advanced maternal age, says Dr Ndegwa-Njuguna, should not be considered a complete barrier. "There are factors that determine when a woman decides to have a baby ; do you have the money, a partner...is the time right for you? Age shouldn't be considered a complete barrier. These are just risks. It is not a given that you'll suffer any of these problems."

A study in the Current Opinion in Obstetrics and Gynecology reports that uterine aging can be compensated for by hormonal means, and egg quality can be compensated for with donations from young women; obstetrical complications among older women could be minimized with good screening and modern obstetrical care.

SO WHAT TO DO IF OVER 35 AND BROODY?

When you're over 35 and planning to have a baby, Dr Ndegwa-Njuguna advises that you should have regular hospital visits and care such as folic supplementation, eating healthy foods (which includes plenty of fruits and vegetables), and regular exercise so that the body is fit enough to carry a pregnancy to term. "Being overweight is a big problem. It reduces the likelihood of your getting pregnant and even when you are, obesity increases your chances of hypertension and diabetes. Exercise regularly but don't overdo it. Walking half an hour a day is good enough. Swimming is excellent because it engages the whole body. Light aerobics and yoga also count," she says.

"Women who have postponed motherhood tend to have enormous social and cultural pressure to deal with on a daily basis," says Ruth Mwangi, a counseling psychologist with Life Pillars Counseling and Consultancy. "Particularly in more conservative contexts, they are constantly seen as 'different' and this can negatively impact on self-esteem and even social interactions."

Ultimately, Mwangi says, every woman has to make choices in life that are in their best interest and in motherhood, for the baby.